April Weber

April Weber

Monday, 04 April 2011 17:33

Coffee Industry

General Overview

Coffee as a beverage was introduced in Europe during the sixteenth century, first in Germany and then throughout the European continent during the following century, especially to France and Holland. Afterwards, it spread to the rest of the world.

Since coffee will not keep its characteristic smell and flavour for long, after roasting and grinding, industrial establishments to roast and grind coffee have become needed wherever coffee is consumed. The establishments are usually small or medium-sized plants, but large factories do exist, mainly to produce regular as well as instant (soluble) coffee.

It is difficult to estimate the number of workers employed by the coffee industry. Some of the smaller plants do not keep registries, and figures are not entirely reliable. Considering a total consumption of approximately 100 million 60 kg bags of coffee during the year 1995, the worldwide coffee trade represents about US$50 million. Table 1 lists selected coffee-importing countries, giving an idea of the present world consumption.

Table 1. Selected coffee importers (in tonnes).

Country

1990

1991

1992

United States

1,186,244

1,145,916

1,311,986

France

349,306

364,214

368,370

Japan

293,969

302,955

295,502

Spain

177,681

176,344

185,601

United Kingdom

129,924

119,020

128,702

Austria

108,797

118,935

125,245

Canada

120,955

126,165

117,897

Source: FAO 1992.

 

Coffee manufacturing is a relatively simple process, including cleaning, roasting, grinding and packing processes, as shown in figure 1. However, modern technology has led to complex processes, with an increase in speed of production and requiring laboratories for quality-control testing of the product.

Figure 1. Flow chart of coffee manufacturing.

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Coffee beans arrive at factories in 60 kg bags, which are unloaded mechanically or manually. In the latter case, usually two workers hold a bag and place it upon another worker’s head. This worker will carry the bag to be stored. Even when transportation is done on coveyor belts, some physical effort with high energy consumption is required.

The use of instant coffee has steadily increased, reaching approximately 20% of the world consumption. Instant coffee is obtained through a complex process in which blasts of hot air blow over coffee extracts, followed by evaporation, cooling and lyophilization (freeze drying), varying in details from one factory to another. In the manufacture of decaffeinated coffee, which represents over 10% of the consumption in the United States and in Europe, some plants still utilize chlorinated solvents (such as methylene chloride), which is removed by a blast of water vapour.

Potential Risks and Health Effects

To start coffee processing, bags are opened with a small knife, and the beans are thrown inside a bin to be cleaned. The work area is noisy and a large amount of residual particulate material remains in suspension, released from the cleaning machine.

Roasting exposes workers to risks of burns and thermal discomfort. Bean mixing, or blending, is done automatically, as is grinding, in areas which may be deficient in lighting due to interference from suspended coffee dust. Dirt may accumulate, noise levels may be high and mechanization requires work at a high speed.

After grinding, bags of different materials and sizes are filled and then packed, usually in cardboard boxes. When performed manually, these operations require high-speed repetitive motion of hands and arms. Cardboard boxes are transported to storage areas and then to their final destination.

The strong odour characteristic of the coffee industry may bother workers inside the plants, and the surrounding community as well. The significance of this problem as a potential health risk has not yet been clarified. The odour of coffee is due to a mixture of different products; research is ongoing to identify individual effects of these chemicals. Some components of the coffee dust and some of the odour-producing substances are known to be allergens.

Potential risks in instant-coffee plants are similar to those in regular coffee production; in addition, there are risks due to hot steam and boiler explosions. In the removal of caffeine, even when performed automatically, the risk of solvent exposure may be present.

Other potential risks which may affect workers’ health are similar to those found in food industries in general. Risks for accidents arise from cuts from knives used in bag opening, burns during roasting and crushing during grinding operations, especially in old machinery without automatic machine guarding. There are fire and explosion hazards from the large amounts of dust, unsafe electric wiring and gas used for heating the roasters.

Several hazards may be found in the coffee industry including, among others: hearing loss due to excessive noise, thermal stress during roasting, poisoning from pesticides and musculoskeletal disorders, especially affecting the backs of workers who lift and carry heavy bags.

Allergic disorders affecting the eye, skin or respiratory system may occur in any area in a coffee plant. It is the coffee dust which is associated with bronchitis with lung function impairment; rhinitis and conjunctivitis are also concerns (Sekimpi et al. 1996). Allergic reactions to contaminants of bags previously used for other materials, such as castor bean seeds, have also occurred (Romano et al. 1995).

Repetitive-motion disorders may result from high-speed motion in packing operations, especially where workers are not warned of the risk.

In less developed countries, effects of occupational risks may develop early because conditions of work may be inadequate and, moreover, other social and public health factors may contribute to disease. Such factors include: low salaries, inadequate medical care and social security, improper housing and sanitation, low levels of education, illiteracy, endemic diseases and malnutrition.

Preventive Measures

Machine guarding, general ventilation and local exhaust systems, noise abatement, housekeeping and cleaning, decreased bag weights, substitutes of solvents used in caffeine extraction, periodic inspection and preventive maintenance of boilers are examples of preventive measures that are required for ensuring adequate levels of industrial hygiene and safety. Odour intensity may be reduced through modification of roasting procedures. The organization of work can be modified so that repetitive-motion disorders may be avoided through alteration of working position and rhythm, as well as the introduction of systematic breaks and regular exercises, among other practices.

Periodic health screening should stress evaluation of exposure to herbicides and pesticides, spinal disorders and early signs of repetitive-motion disorders. Scratch tests using extracts from coffee beans, even if not universally accepted as completely reliable, may be useful in the identification of hypersusceptible individuals. Lung function tests may aid in the early diagnosis of obstructive respiratory conditions.

Health education is an important instrument to enable workers to identify health risks and their consequences and to become aware of their right to a healthy working environment.

Governmental action is required, through legislation and enforcement; employers’ participation is needed in providing and maintaining adequate working conditions.

 

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Monday, 04 April 2011 17:26

Soft Drink Bottling and Canning

In most established markets around the world, soft drinks now rank first among manufactured beverages, surpassing even milk and coffee in terms of per capita consumption.

Including ready-to-drink, packaged products and bulk mixes for fountain dispensing, soft drinks are available in almost every conceivable size and flavour and in virtually every channel of retail distribution. Complementing this universal availability, much of the soft drink category’s growth can be attributed to convenient packaging. As consumers have become increasingly mobile, they have opted for easier-to-carry packaged goods. With the advent of the aluminium can and, more recently, the resealable plastic bottle, soft drink packaging has become lighter and more portable.

Stringent quality-control standards and state-of-the-art water treatment processes also have afforded the soft drink industry a high degree of confidence regarding product purity. Moreover, the manufacturing or bottling plants that produce soft drinks have evolved into highly mechanized, efficient and spotlessly clean food-processing facilities.

As early as the 1960s, most bottlers were producing beverages through machinery that ran at 150 bottles per minute. As product demand has continued to skyrocket, soft drink manufacturers have shifted to faster machinery. Thanks to advances in production technology, filling lines now are able to run in excess of 1,200 containers per minute, with minimal downtime except for product or flavour changes. This highly automated environment has allowed soft drink manufacturers to reduce the number of employees required to operate the lines (see figure 1). Still, as production efficiencies have risen dramatically, plant safety has remained an ever-important consideration.

Figure 1. Control panel in an automated soft drink plant in Novosibirsk, Russia.

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Soft drink bottling or manufacturing involves five major processes, each with its own safety issues that must be evaluated and controlled:

  1. treating water
  2. compounding ingredients
  3. carbonating product
  4. filling product
  5.  packaging.

 

See figure 2.

Figure 2. Flow chart of basic bottling operations.

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Soft drink manufacturing starts with water, which is treated and cleansed to meet exacting quality-control standards, usually exceeding the quality of the local water supply. This process is critical to achieving high product quality and consistent taste profiles.

As ingredients are being compounded, the treated water is piped into large, stainless-steel tanks. This is the stage at which various ingredients are added and mixed. Diet beverages are mixed with artificial, non-nutritive sweeteners such as aspartame or saccharin, whereas regularly sweetened drinks typically use liquid sugars like fructose or sucrose. It is during this stage of the production process that food colouring may be added. Flavoured, sparkling waters receive the desired flavouring at this stage, while plain waters are stored in the mixing tanks until the filling line calls for them. It is common for bottling companies to purchase concentrate from other firms.

In order for carbonation (absorption of carbon dioxide (CO2)) to occur, soft drinks are cooled using large, ammonia-based refrigeration systems. This is what gives carbonated products their effervescence and texture. CO2 is stored in a liquid state and piped into carbonation units as needed. This process can be manipulated to control the required rate of beverage absorption. Depending upon the product, soft drinks may contain from 15 to 75 psi of CO2. Fruit-flavoured soft drinks tend to have less carbonation than colas or sparkling water. Once carbonated, the product is ready to be dispensed into bottles and cans.

The filling room usually is separated from the rest of the facility, protecting open product from any possible contaminants. Again, the highly automated filling operation requires a minimal number of personnel. See figure 3 . Filling room operators monitor the equipment for efficiency, adding bulk lids or caps to the capping operation as necessary. Empty bottles and cans are transported automatically to the filling machine via bulk material-handling equipment.

Figure 3. Soft drink canning line showing filling operations.

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Stringent quality-control procedures are followed throughout the production process. Technicians measure many variables, including CO2, sugar content and taste, to ensure that finished drinks meet required quality standards.

Packaging is the last stage prior to warehousing and delivery. This process also has become highly automated. Meeting various marketplace requirements, bottles or cans enter the packaging machinery and may be wrapped with cardboard to form cases or placed into reusable plastic trays or shells. The packaged products then enter a palletizing machine, which automatically stacks them onto pallets. (See figure 4.) Next, the loaded pallets are moved—typically via fork-lift—to a warehouse, where they are stored.

Figure 4. Eight-packs of 2-litre soft drink plastic bottles on the way to an automatic palletizer.

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Hazard Prevention

Lifting-related injuries—especially to employees’ backs and shoulders—are not uncommon in the beverage business. While many technological advances have been made in material handling over the years, the industry continues to seek safer, more efficient ways to move heavy product.

Certainly, employees must be provided with the proper training on safe work practices. Injuries also can be minimized by limiting exposure to lifting through enhanced work-station design. Adjustable tables can be used to raise or lower material to waist level, for example, so that employees do not have to bend and lift as much. In this manner, most weight-related stress is transferred to a piece of equipment instead of the human body. All beverage manufacturers should implement ergonomics programmes that identify work-related hazards and minimize the risks—either through modification or by developing better equipment. A reasonable means to that end is job rotation, which reduces employee exposure to high-risk tasks.

The use of machine guarding is another critical component of safe beverage manufacturing. Equipment such as fillers and conveyors move at high speeds and, if left unguarded, could snag employee clothing or body parts, causing potentially severe injuries. Conveyors, pulleys, gears and spindles must have appropriate covers to prevent employee contact. Overhead conveyors can create an additional hazard of falling cases. Netting or wire-mesh screens should be installed to protect against this danger. Maintenance programmes should dictate that all guarding which is removed for repair be replaced as soon as repair work is completed.

Since wet conditions are prevalent in the filling room, adequate drainage is necessary to keep liquid from accumulating on nearby walkways. In order to avoid slip-and-fall injuries, proper efforts must be made to keep floors as dry as possible. While steel-toed shoes usually are not required in the filling room, slip-resistant soles are highly recommended. Shoes should be selected based on the slip coefficient of the sole. Additionally, all electrical equipment should be properly grounded and protected from any moisture. Employees must take precautions to dry the areas around equipment before any electrical work begins.

Good housekeeping practices and routine inspections also are beneficial in keeping the workplace hazard-free. By taking these comparatively simple steps, management can be sure that all equipment is in good operating condition and properly stored. Emergency equipment such as fire extinguishers and eyewash stations also should be inspected for proper operation.

Although most of the chemicals present in bottling plants are not extremely hazardous, every operation uses flammable substances, acids, caustics, corrosives and oxidants. Appropriate work practices should be developed so employees know how to work safely with these chemicals. They must be taught how properly to store, handle and dispose of the chemicals and how to wear protective gear. Training should cover the location and operation of emergency response equipment. Eyewash stations and showers can minimize injury to anyone who is accidentally exposed to a hazardous chemical.

It also is necessary to install equipment such as chemical booms and dykes, as well as absorbent material, to be used in the event of a spill. Properly designed hazardous chemical storage facilities will minimize the risk of employee injury, too. Flammables should be separated from corrosives and oxidants.

The large tanks used for mixing ingredients, which need to be entered and cleaned routinely, are considered confined spaces. See the box on confined spaces in this chapter for information on the related hazards and precautions.

Mechanized equipment has become increasingly complex, often controlled by remote computers, pneumatic lines or even gravity. Employees must be sure that this equipment has been de-energized before it is serviced. Proper de-energizing procedures must be developed to guarantee the safety of those who maintain and repair this equipment. Energy must be shut off and locked out at its source so that the unit being serviced cannot be accidentally energized, causing potentially fatal injuries to service employees or nearby line operators.

Safety training and written de-energizing procedures are critical for each piece of equipment. Emergency stop switches should be strategically placed on all equipment. Interlocked safety devices are used to stop the equipment automatically when doors are opened or light beams are interrupted. Employees must be informed, however, that these devices cannot be relied upon to completely de-energize the equipment, but only to stop it in an emergency. Emergency stop switches cannot take the place of a proven de-energizing procedure for equipment maintenance.

Chlorine, which is used in the water treatment area, could be hazardous in the event of an accidental release. Chlorine typically comes in steel cylinders, which should be stored in an isolated, well-ventilated area and secured from tipping. Employees should be trained to follow safe cylinder-changing procedures. They also should be taught how to take quick, decisive action if an accidental release of chlorine occurs. In the late 1990s new chlorine compounds are gradually replacing the need for chlorine gas. Although still hazardous, these compounds are much safer to handle than gas.

Ammonia is used as a refrigerant in bottling operations. Typically, large ammonia systems can create a health hazard in the event of a leak or a spill. Bottling facilities should develop emergency response procedures to identify the responsibilities of involved employees. Those who are required to respond to such an emergency must be trained in spill response and respirator use. In the event of a leak or spill, respirators should be immediately available, and all non-essential personnel evacuated to safe areas until the situation is controlled.

CO2, which is used in the filling operation, also can create health concerns. If filling rooms and adjacent work areas are not adequately ventilated, CO2 accumulation can displace oxygen in employees’ breathing zones. Facilities should be monitored regularly for elevated CO2 levels and, if they are detected, ventilation systems should be inspected to determine the cause for this occurence. Additional ventilation may be required to correct the situation.

Technological advances have made available better sound-absorption material for insulating or muffling motors and gears in most equipment. Still, given the function and size of filling equipment, noise levels generally exceed 90 dBA in this area. Employees who are exposed to this level of noise for an 8-hour weighted average must be protected. Good hearing protection programmes should include research on better ways to control noise; employee education on related health effects; personal noise protection; and training on how to use hearing protection devices, the wearing of which must be enforced in high-noise areas. Employee hearing must be routinely checked.

Fork-lifts are operated throughout the bottling plant and their safe use is imperative. In addition to demonstrating their driving skills, potential operators must understand fork-lift safety principles. Licenses are commonly issued to show that a minimum level of competency has been achieved. Fork-lift safety programmes should include a pre-use inspection process, whereby the vehicles are checked to ensure that all safety equipment is in place and working. Any deficient conditions should be immediately reported and corrected. Gas or liquid petroleum (LP) fork-lifts generate carbon monoxide as a by-product of combustion. Such emissions can be minimized by keeping the fork-lift engines tuned to manufacturers’ specifications.

Personal protective equipment (PPE) is common throughout the bottling facility. Filling-room employees wear eye and ear protection. Sanitation crews wear face, hand and foot protection that is appropriate for the chemicals they are exposed to. While slip-resistant shoes are recommended throughout the plant, maintenance employees should also have the added protection of steel-toed shoes. The key to a good PPE programme is to identify and evaluate the potential hazards associated with each job and to determine whether those hazards can be eliminated through engineering changes. If not, PPE must be selected to address the specific hazard at hand.

Management’s role is critical in identifying hazards and developing practices and procedures to minimize them in the workplace. Once developed, these practices and procedures must be communicated to employees so that they can perform their jobs safely.

As plant technology continues to advance—providing better equipment, new guards and protective devices—soft drink bottlers will have even more ways to maintain the safety of their workforce.

 

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Monday, 04 April 2011 17:24

Soft Drink Concentrate Manufacturing

Process Overview

The making of the concentrate is the first step in the production of a carbonated soft drink. At the beginnings of the industry, in the nineteenth century, both concentrate and soft drink were manufactured in the same facility. Sometimes the concentrate was sold to the consumers, who would make their own soft drinks. As the carbonated soft drink business has grown, the concentrate and the soft drink manufacturing have become specialized. Today, a concentrate manufacturing plant sells its product to various bottling companies.

Concentrate plants are constantly optimizing their operation through systems automation. As the demand for concentrate increases, automation has allowed the manufacturer to satisfy the demand without expanding the size of the manufacturing plant. Packaging size has increased too. Early in the industry, 1/2-, 1- and 5-gallon containers were the most common. Today 40- and 50-gallon drums and even tank trucks with capacities of 3,000 to 4,000 gallons are used.

Operations in a concentrate manufacturing plant can be divided into five basic processes:

  1. treating water
  2. receiving raw materials
  3. concentrate manufacturing
  4. concentrate and additives filling
  5. shipping finished products.

 

Each of these processes has safety hazards that must be evaluated and controlled. Water is a very important ingredient in the concentrate and it must have excellent quality. Each concentrate plant treats water until it reaches the desired quality and is free from micro-organisms. Water treatment is monitored during all stages.

When the plant receives the compounding ingredients, inspection, sampling and analysing of the ingredients in the quality-control department are begun. Only materials that have passed the tests will be used in the concentrate manufacturing process. Some of the raw materials are received in tank trucks and require special handling. Also, packaging material is received, evaluated and analysed in the same way as the raw materials.

During the manufacturing of concentrate, treated water and liquid and solid ingredients are pumped into stainless-steel tanks, where they are mixed, homogenized and/or extracted in accordance with the manufacturing instructions. The tanks have capacities of 50 gallons, 10,000 gallons and even more. These tanks are completely clean and sanitized at the time of mixing.

Once the concentrate is manufactured, the filling stage is started. All the products are piped into the filling room. Filling machines are strictly cleaned and sanitized before the filling process starts. Most of the filling machines are dedicated to specific container sizes. The product is kept inside pipes and tanks at times during the filling process in order to avoid contamination. Each container should be labelled with the product name and handling hazards (if necessary). Full containers are moved by conveyors to the packaging area. Containers are placed on pallets and wrapped in plastic or tied before they are stored. Besides the concentrates, additives to be used in the preparation of carbonated soft drinks are packed. Many of these additives are packed in plastic bags and placed in boxes.

Once at the warehouse, the products are divided and prepared to be sent to the different bottling companies. These products should be labelled following all government regulations. If products are going to another country, the product must be labelled in accordance with the other country’s labelling requirements.


Production of fruit juices

Fruit juices are made from a wide variety of fruits, including oranges and other citrus fruits, apples, grapes, cranberries, pineapples, mangoes and so forth. In many cases, various fruit juices are blended. Usually, the fruit is processed into a concentrate near where it is grown, then shipped to a fruit juice packager. Fruit juices can be sold as concentrates, frozen concentrates (especially orange juice) and as the diluted juice. Often sugar and preservatives are added.

Once received at the processing plant, the oranges are washed, graded to remove damaged fruit, separated according to size and sent to the juice extractors. There the oils are extracted from the peel, and then the juice extracted by crushing. The pulpy juice is screened to remove seeds and pulp, which often end up as cattle feed. If the orange juice is intended for sale as “not from concentrate”, it is then pasteurized. Otherwise the juice is sent to evaporators, which remove most of the water by heat and vacuum, then chilled, to produce the frozen, concentrated orange juice. This process also removes many oils and essences which are blended back into the concentrate before shipping to the juice packager.

The frozen concentrate is shipped to the packager in refrigerated trucks or tankers. Many dairies package orange juice using the same equipment used to package milk. (See the article “Dairy products industry” elsewhere in this volume.) The concentrate is diluted with filtered water, pasteurized and packaged under sterile conditions. Depending on the amount of water added, the final product can be cans of frozen orange juice concentrate or ready-to-serve orange juice.

Michael McCann


Hazard Prevention

Hazards in a concentrate manufacturing plant vary depending on the products manufactured and the size of the plant.

Concentrate plants have a low injury rate due to a high degree of automation and mechanized handling. Materials are handled by fork-lifts, and full containers are placed on pallets by automatic palletizers. Although, employees generally do not have to use excessive force to get the job done, lifting related injuries remain a concern. Major hazards include engines and equipment in motion, objects falling from overhead containers, energy hazards in repair and maintenance, confined space hazards in cleaning mixing tanks, noise, fork-lift accidents and hazardous chemical cleaning agents. See the article “Soft drink bottling and canning” for more information on hazards and precautions.

 

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Monday, 04 April 2011 17:22

Production of Fruit Juices

Fruit juices are made from a wide variety of fruits, including oranges and other citrus fruits, apples, grapes, cranberries, pineapples, mangoes and so forth. In many cases, various fruit juices are blended. Usually, the fruit is processed into a concentrate near where it is grown, then shipped to a fruit juice packager. Fruit juices can be sold as concentrates, frozen concentrates (especially orange juice) and as the diluted juice. Often sugar and preservatives are added.

Once received at the processing plant, the oranges are washed, graded to remove damaged fruit, separated according to size and sent to the juice extractors. There the oils are extracted from the peel, and then the juice extracted by crushing. The pulpy juice is screened to remove seeds and pulp, which often end up as cattle feed. If the orange juice is intended for sale as “not from concentrate”, it is then pasteurized. Otherwise the juice is sent to evaporators, which remove most of the water by heat and vacuum, then chilled, to produce the frozen, concentrated orange juice. This process also removes many oils and essences which are blended back into the concentrate before shipping to the juice packager.

The frozen concentrate is shipped to the packager in refrigerated trucks or tankers. Many dairies package orange juice using the same equipment used to package milk. (See the article “Dairy products industry” elsewhere in this volume.) The concentrate is diluted with filtered water, pasteurized and packaged under sterile conditions. Depending on the amount of water added, the final product can be cans of frozen orange juice concentrate or ready-to-serve orange juice.

 

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Monday, 04 April 2011 17:02

General Profile

Overview of the Sector

The beverage industry consists of two major categories and eight sub-groups. The non-alcoholic category is comprised of soft drink syrup manufacture; soft drink and water bottling and canning; fruit juices bottling, canning and boxing; the coffee industry and the tea industry. Alcoholic beverage categories include distilled spirits, wine and brewing.

Evolution of the industry

Although many of these beverages, including beer, wine and tea, have been around for thousands of years, the industry has developed only over the past few centuries.

The beverage products industry, viewed as an aggregate group, is highly fragmented. This is evident by the number of manufacturers, methods of packaging, production processes and final products. The soft drink industry is the exception to the rule, as it is quite concentrated. Although the beverage industry is fragmented, ongoing consolidation since the 1970s is changing that.

Since the early 1900s beverage companies have evolved from regional firms that mainly produced goods for local markets, to today’s corporate giants that make products for international markets. This shift began when companies in this manufacturing sector adopted mass production techniques that let them expand. Also during this time period there were advances in product packaging and processes that greatly increased product shelf life. Air-tight containers for tea prevented absorption of moisture, which is the principle cause of loss of flavour. In addition, the advent of refrigeration equipment enabled lager beers to be brewed during the summer months.

Economic importance

The beverage industry employs several million people worldwide, and each type of beverage grosses billions of dollars in revenue each year. Indeed, in several small, developing countries, the production of coffee is the major support of the entire economy.

Characteristics of the Workforce

Though the ingredients and production of beverages vary, generally the characteristics of those employed in this industry have many commonalties. The process of harvesting raw materials, whether they be coffee beans, barley, hops or grapes, employs low-income, unskilled individuals or families. In addition to being their main source of income, the harvest determines a large part of their culture and lifestyle.

In contrast, the processing of the product involves automated and mechanized operations, usually employing a semi-skilled, blue-collar workforce. In the production facility and warehouse areas, some of the common jobs include packaging and filling machine operator, fork-lift operator, mechanic and manual labourer. The training for these positions is completed onsite with extensive on-the-job instruction. As technology and automation evolve, the workforce diminishes in number and technical training becomes more important. This semi-skilled manufacturing workforce is usually supported by a highly skilled technical group consisting of industrial engineers, manufacturing managers, cost accountants and quality assurance/food safety technicians.

The beverage industry for the most part distributes its products to wholesalers using common carriers. However, soft drink manufacturers usually employ drivers to deliver their products directly to individual retailers. These drivers-salesworkers account for about one-seventh of the workers in the soft drink industry.

The more health-conscious atmosphere in Europe and North America in the 1990s has led to a flat market in the alcoholic beverage industry, with demand shifting to non-alcoholic beverages. Both alcoholic and non-alcoholic beverages, however, are expanding considerably in developing nations in Asia, South America and to some extent Africa. Because of this expansion, numerous local jobs are being created to meet production and distribution needs.

 

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Monday, 04 April 2011 16:45

Warehousing

Warehousing has long been a global industry; warehouses are integrally linked to commerce and transportation of goods—by rail, sea, air and road. Warehouses may be classified by the type of products stored: food products stored in dry, chilled or frozen sections; clothing or textiles; construction equipment or materials; machinery or machine parts. In the United States in 1995, for exemple, 1,877,000 workers were employed in trucking and warehousing (BLS 1996); this statistic cannot presently be disaggregated into workers by warehouse type or category. Warehouses might sell directly to external (retail) or internal (wholesale) customers, and the quantities retrieved for customers may be either full-pallet or less-than-full-pallet (one or more cases selected from a single pallet). Mechanical means (fork-lifts, conveyors or automatic storage and retrieval systems (AS/RS)) may be used to transport full-pallet or less-than-full-pallet loads; or workers, working without pallet movers and conveyors, may manually handle stored materials. Regardless of the nature of the business, the products stored or the mode of transportation servicing the warehouse, the basic layout is quite uniform, although the operational scale, terminology and technology will likely differ. (For additional information on AS/RS in warehousing, see Martin 1987.)

Products are delivered by shippers or suppliers to a receiving dock, where they are then entered into either a manual or computerized inventory system, assigned a storage rack or “slot” location (an address) and then transported to that location, usually by mechanical means (conveyors, AS/RS, fork-lift trucks or tractors). Once a customer order is received, the desired containers or cases must be retrieved from their slot location. Where full pallets are retrieved, mechanical means (a fork-lift or tractor operator) are used (see figure 1). When less than a full pallet load (one or more cases from a rack or slot) is to be retrieved, manual material handling is required, using a worker called a selector, who will choose the desired number of cases and place them either onto a mechanical pallet mover, a push cart or a conveyor. The individual customer order is assembled onto a pallet or similar container for shipment to the customer; a label, tag or other mark containing invoice/billing and/or routing instructions is then applied. This task may be performed by the order selector or fork-lift operator, or, where conveyors are used to deliver single cases for final assembly, by an assembler. When the order is ready for shipment, it is loaded by mechanical means onto the truck, trailer, railroad car or ship. (See figure 2).

Figure 1. A fork-lift truck in a warehouse in the United Kingdom being loaded with apples.

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Figure 2. A dockworker in the United Kingdom using lifting machines to move quarters of beef.

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Approximately 60% of the work activity in the warehouse is directly related to travel; the remainder relates to manual material handling. Aside from the important work of clerks, dispatchers, cleaners, supervisors and managers, the main work of the warehouse relating to the transporting and handling of goods is performed primarily by two classes of workers: fork-lift operators and selectors.

Intense worldwide competition and the rapid entrance of new firms have created the drive for increased labour and space efficiency, spawning a new discipline called warehouse management systems (WMSs) (Register 1994). These systems are becoming increasingly less expensive and more powerful; they rely on computer networks, bar coding, computer software and radio-frequency communications systems to vastly increase management and control of warehouse inventory and operations, allowing warehouses to improve customer order response times and responsiveness while dramatically increasing inventory accuracy and reducing costs (Firth 1995).

WMSs essentially computerize inventory and order dispatch systems. When incoming product from a supplier or shipper arrives at the receiving dock, bar code scanners record the product code and name, instantly updating the inventory database while assigning the incoming product an address in the warehouse. A fork-lift operator is then alerted to pick up and deliver the stock via a radio-frequency communications system mounted on the vehicle.

Orders from customers are received by another computer program which looks up the product address and availability of each item ordered in the inventory database and then sorts the customer order by the most efficient travel path to minimize travel. Labels with the product name, code and location are printed out for use by the order selectors who must then fill this order. While these features clearly help improve customer service and improve efficiency, they are important preconditions for engineered work standards (EWSs), which may pose additional health and safety hazards for both fork-lift operators and order selectors.

Information about each order—the number of cases, travel distances and so on—which is generated by the order dispatch programme can be further combined with standard or allowed times for each activity to calculate an overall standard time for selecting a particular customer order; it would be extremely time-consuming and difficult to retrieve this information without the use of the computer hardware and databases. Computer monitoring can then be used to record the elapsed time on each order, compare the actual with the allowed time and then compute an efficiency index, which any supervisor or manager can look up by pressing a few computer keys.

Warehouse EWSs have spread from the United States to Australia, Canada, the United Kingdom, Germany, Austria, Finland, Sweden, Italy, South Africa, the Netherlands and Belgium. While WMS systems themselves do not necessarily add safety and health hazards, there is considerable evidence to suggest that the resulting increased workload, lack of control over work pace and the impact of increased frequency of lifting contribute significantly to increased injury risk. In addition, the time pressure imposed by work standards may force workers to take risky short cuts and not utilize proper safe work methods. These risks and hazards are described below.

Hazards

In the most basic warehouse, regardless of the level of technology and computerization, there are a myriad of basic health and safety hazards; modern WMSs can be linked with a different order of health and safety hazards.

Basic health hazards begin with potentially toxic materials which may be stored in warehouses; examples include petroleum products, solvents and dyestuffs. These require proper labelling, employee education and training and an effective hazard communication programme (including MSDSs) for all affected workers, who often know little about the health effects of what they are handling, much less proper handling, spill and clean-up procedures. (See, for example, the ILO Chemicals Convention, 1990 (No. 170), and Recommendation, 1990 (No. 177).) Noise may be present from gasoline or LP-powered fork-lifts, conveyors, ventilation systems and pneumatically-actuated equipment. Additionally, workers who operate such equipment may be subject to whole-body vibration. (See, for example, the ILO Working Environment (Air Pollution, Noise and Vibration) Convention, 1977 (No. 148), and Recommendation, 1977 (No. 156).)

Both fork-lift operators and selectors may be exposed to diesel and gasoline exhaust from trucks at the loading and receiving docks, as well as from fork-lifts. Lighting may not be adequate for fork-lift and other vehicle traffic or for ensuring proper identification of products desired by customers. Workers assigned to work in cold and frozen storage areas may experience cold stress from exposure to cold temperatures and air recirculation systems; temperatures in many freezer storage areas can approach –20ºC, even without wind chill factors being considered. Moreover, since few warehouses are air conditioned during warm months, warehouse workers, particularly those performing manual material handling, may be exposed to heat stress problems.

Safety hazards and risks are also many and varied. Besides the more obvious hazards evident when pedestrians and any motor-driven vehicle are put into the same work area, many of the injuries occurring among warehouse workers include slips, trips and falls from floors not kept free of ice, water or spilled product or that are poorly maintained; a number of injuries involve fork-lift operators who slip or fall while mounting or dismounting their fork-lift trucks.

Workers are often exposed to falling product from overhead racks. Workers may be caught in or between fork-lift masts, forks and cargo, resulting in serious physical injury. Wooden pallets handled by workers often result in exposure to slivers and related puncture wounds. Using knives to cut apart boxes and cases often results in cuts and lacerations. Workers who move boxes or containers on or off conveyors may be exposed to in-running nip points. Selectors, assemblers and other workers engaged in manual material handling are exposed to varying degrees of risk of developing low-back pain and other related injuries. Weight-lifting regulations and recommended methods for materials handling are discussed elsewhere in the Encyclopaedia.

Recordable injuries and lost workday cases in the US warehouse industry, for example, are considerably higher than those for all industry.

Data regarding injuries (and particular back injuries) among grocery order selectors, the group at greatest risk from lifting-related injuries, are not available on a national or international scale. The US NIOSH, however, has studied lifting and other related injuries at two grocery warehouses in the United States (see US NIOSH) and found that “all order selectors have an elevated risk for musculoskeletal disorders, including low-back pain, because of the combination of adverse job factors, all contributing to fatigue, a high metabolic load and the workers’ inability to regulate their work rate because of the work requirements” (NIOSH 1995).

A comprehensive application of ergonomics to the warehouse should not be confined to lifting and to order selectors. A wide focus is required, involving detailed job analysis, careful measurement and assessment (part of the job analysis begins with the job safety analyses below). A more comprehensive look at the design of racks and shelves is required, as is establishment of a closer working relationship with suppliers to design or retrofit fork-lift controls to reduce ergonomic risk factors (extensive reaches, foot flexion and extension, winging, awkward neck and body positions) and to design containers that are less heavy and bulky, with handles or grips to reduce lifting risk.

Corrective Actions

Basic health hazards

Employers, workers and trade unions should cooperate to develop and implement an effective hazard communication programme which emphasizes the three following fundamentals:

  1. adequate labelling of all toxic substances
  2. availability of detailed MSDSs that provide more detailed information about health effects, fire, reactivity, PPE, first aid, spill clean-up and other emergency procedures
  3. regular and relevant worker training in proper handling of these substances.

 

Lack of an effective hazard communication programme is one of the most frequent standards violations cited in this industry by the US Occupational Safety and Health Administration (OSHA).

Noise and vibration from mechanical equipment, conveyors and other sources require frequent noise and vibration testing and worker training, as well as engineering controls where needed. These controls are most effective when applied at the source of the noise in the form of noise insulation, mufflers and other controls (since most fork-lift operators are seated on top of the engine, vibration and noise dampening at this point are generally most effective). Lighting should be checked frequently and maintained at levels sufficient to reduce vehicle-pedestrian accidents and ensure that product identification and other information can be easily read. Heat (or cold) stress prevention programmes should be implemented for workplaces in warm and humid climates and for selectors or fork-lift operators assigned to cold storage or freezer rooms, to ensure that workers receive adequate breaks, fluids, training and information and that other preventive measures are implemented. Finally, where diesel or petroleum-based fuels are used, exhaust systems should be periodically tested for emissions of carbon monoxide and nitrogen oxides to ensure that they are within safe levels. Proper maintenance of vehicles and restricting their use to adequately ventilated areas will also help reduce the risk of over-exposure to these emissions.

Safety hazards for fork-lift and vehicle operators

Vehicle-pedestrian accidents are a constant risk in any warehouse. Pedestrian lanes should be clearly marked and respected. All vehicle operators should receive training in the safe operation of the vehicle, including traffic rules and speed limits; refresher training should also be considered. Mirrors should be installed at busy intersections or at blind corners to enable vehicle operators to check for traffic or pedestrians before proceeding, and operators should sound their horn before proceeding; back-up beepers or signals may also be considered. Dockplates from loading and receiving docks to the truck, railroad car or barge need to be sufficient to support the load and adequately secured.

Table 2 gives a job safety analysis for fork-lift operators, with recommendations.

Table 2. Job safety analysis: Fork-lift operator.

Job elements or tasks

Hazards present

Recommended protective actions

Mounting/dismounting fork-lift

Slipping/tripping on floor (grease, water, cardboard) during mounting/dismounting; back or shoulder strain from repeated incorrect entry/exit and bumping head on protective structure

Proper maintenance and clean-up of floors, particularly in high-traffic areas; exercising caution when mounting/dismounting; using three-point method to get in and out of fork-lift cab, being careful not to bump your head on overhead protective structure: grasping the support beams for the overhead protective structure with both hands, placing the left foot into the foot-hold (if one is provided) and then pushing off with the right foot and levering oneself into the cab.

Driving with and without loads

Pedestrian traffic and other vehicles might cross path suddenly; inadequate lighting; noise and vibration hazards; turning and twisting neck into awkward postures; steering may require wrist deviation, winging and/or excessive force; brake and accelerator pedals often require awkward foot and leg posture together with static loading

Slowing down in high traffic areas; waiting and sounding horn at all crossings with other aisles; exercising caution around other pedestrians; observing speed limits; ensuring proper lighting is provided and maintained through periodic inspections of illumination; installing and maintaining material that dampens noise and vibration on all vehicles and equipment; regular noise testing; operators should twist their upper torso at their waist, not at their neck, particularly when looking behind mirrors installed on the fork-lift and throughout the work facility will also help reduce this risk factor; purchasing, retrofiting and maintaining power steering and steering wheels which can tilt and raise to fit operators and avoiding winging; providing frequent rest breaks for recovery from static loading fatigue; considering redesign of foot pedals to reduce angle of foot (extension) and by hinging accelerator pedals to the floor

Raising or lowering forks with or without loads

Leaning and twisting of neck in order to see load clearly; reaching for hand controls which may involve excess reach or winging

Twisting or leaning from the waist, not from the neck; selecting fork-lifts which provide adequate visibility about the mast and which have hand controls within easy reach (located at side of operator, not on control console by steering wheel), but which are not so close or high as to involve winging; possibly retrofiting fork-lifts, with manufacturer’s permission.

Filling gas tanks or changing batteries

Changing LPG or gasoline tanks or batteries may require excessive and awkward lifting

Using at least two employees to lift, or using a mechanical hoist; considering redesign of fork-lift to facilitate a more accessible location for fuel tank

 

Implementing ergonomic solutions will require closer coordination with fork-lift and vehicle manufacturers; relying solely upon operator training and traffic rules will not eliminate hazards by itself. In addition, safety and health regulatory agencies have prepared mandatory standards for the design and use of fork-lifts—for example, requiring overhead guards to offer protection against falling objects (see figure 3).

Figure 3. An overhead guard fitted to a fork-lift truck.

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Safety hazards for order selectors

Table 3 is a job safety analysis listing most of the corrective actions necessary to reduce the safety and lifting hazards for order selectors. However, just as improved fork-lift design to reduce ergonomic risk factors requires closer coordination with vehicle manufacturers, reducing safety and lifting hazards for order selectors requires similar coordination with designers of racking systems, consultants who design and install warehouse control systems and engineered standards systems and the vendors who store their products in the warehouse. The latter can be enlisted to design products that are less bulky, weigh less and have better handles or grips. Rack manufacturers can be very helpful in designing and retrofitting rack systems which allow the selector to stand upright during selection.

Table 3. Job safety analysis: Order selector.

Job elements or tasks

Hazards present

Recommended protective actions

Mounting/dismounting pallet jack

Slipping/tripping on floor (grease, water, cardboard) during mounting/dismounting

Proper maintenance and clean-up of floors, particularly in high-traffic areas; exercising caution when mounting/dismounting

Travel up and down aisles

Pedestrian traffic and other vehicles might cross path suddenly; lighting; noise

Slowing down in high-traffic areas; waiting and sounding horn at all crossings with other aisles; exercising caution around other pedestrians; observing speed limits; ensuring that proper lighting is provided and maintained; installing and maintaining material that dampens noise and vibration on all vehicles and equipment; regular noise testing

Select case from rack, walk to pallet, place case on pallet

Lifting injuries, shoulder, back and neck strain; bumping head on racks; heat stress; cold stress in freezer or cold rooms

Working in conjunction with vendors to reduce container weight to lowest possible levels and to install handles or better grips on bulky or heavy products; storing heavy products at knuckle height or higher; not storing products to require significant lifting over the shoulder, or provide steps, stairs or platforms; providing “turntable” pallets which can be rotated when selecting products, to avoid stretching; modifying carts or pallet jacks to raise higher, to minimize bending and stooping when placing product on the cart or pallet jack; restricting the “cube” of the pallet so that over-the-shoulder lifting is minimized; providing regular heat and cold stress monitoring; providing adequate fluids, conditioning programmes, clothing and frequent rest breaks

Separate pallets to wrap, mark or drop off at loading docks

Slipping/tripping on floor (grease, water, cardboard) during mounting/dismounting

Proper maintenance and clean-up of floors, particularly in high traffic areas; exercising caution when mounting/dismounting

 

Consultants who design and install warehouse control systems and engineered standards need to be more aware of the health and safety risks concerning the effect of work intensification on manual material-handling injuries. NIOSH (1993a, 1995) has recommended that more objective forms of determining fatigue allowance, such as oxygen consumption or heart rate, be used. They have also recommended that the height of the pallet being constructed (the “cube”) be limited to no more than 150 cm, and that there be an “order break” after one pallet has been assembled by the order selector, thus increasing the frequency of recovery periods between orders. In addition to more frequent breaks, NIOSH has recommended restricting overtime for workers based on engineered standards, considering worker rotation and installing “light duty” programmes for order selectors who return from injury or leave.

 

Back

Pipelines, marine vessels, tank trucks, rail tank cars and so forth are used to transport crude oils, compressed and liquefied hydrocarbon gases, liquid petroleum products and other chemicals from their point of origin to pipeline terminals, refineries, distributors and consumers.

Crude oils and liquid petroleum products are transported, handled and stored in their natural liquid state. Hydrocarbon gases are transported, handled and stored in both the gaseous and liquid states and must be completely confined in pipelines, tanks, cylinders or other containers prior to use. The most important characteristic of liquefied hydrocarbon gases (LHGs) is that they are stored, handled and shipped as liquids, taking up a relatively small amount of space and then expanding into a gas when used. For example, liquefied natural gas (LNG) is stored at –162°C, and when it is released the difference in storage and atmospheric temperatures causes the liquid to expand and gasify. One gallon (3.8 l) of LNG converts to approximately 2.5 m3 of natural gas at normal temperature and pressure. Because liquefied gas is much more “concentrated” than compressed gas, more useable gas can be transported and provided in the same size container.

Pipelines

It is generally the case that all crude oils, natural gas, liquefied natural gas, liquefied petroleum gas (LPG) and petroleum products flow through pipelines at some time in their migration from the well to a refinery or gas plant, then to a terminal and eventually to the consumer. Aboveground, underwater and underground pipelines, varying in size from several centimetres to a metre or more in diameter, move vast amounts of crude oil, natural gas, LHGs and liquid petroleum products. Pipelines run throughout the world, from the frozen tundra of Alaska and Siberia to the hot deserts of the Middle East, across rivers, lakes, seas, swamps and forests, over and through mountains and under cities and towns. Although the initial construction of pipelines is difficult and expensive, once they are built, properly maintained and operated, they provide one of the safest and most economical means of transporting these products.

The first successful crude-oil pipeline, a 5-cm-diameter wrought iron pipe 9 km long with a capacity of about 800 barrels a day, was opened in Pennsylvania (US) in 1865. Today, crude oil, compressed natural gas and liquid petroleum products are moved long distances through pipelines at speeds from 5.5 to 9 km per hour by large pumps or compressors located along the route of the pipeline at intervals ranging from 90 km to over 270 km. The distance between pumping or compressor stations is determined by the pump capacity, viscosity of the product, size of the pipeline and the type of terrain crossed. Regardless of these factors, pipeline pumping pressures and flow rates are controlled throughout the system to maintain a constant movement of product within the pipeline.

Types of pipelines

The four basic types of pipelines in the oil and gas industry are flow lines, gathering lines, crude trunk pipelines and petroleum product trunk pipelines.

  • Flow lines. Flow lines move crude oil or natural gas from producing wells to producing field storage tanks and reservoirs. Flow lines may vary in size from 5 cm in diameter in older, lower-pressure fields with only a few wells, to much larger lines in multi-well, high-pressure fields. Offshore platforms use flow lines to move crude and gas from wells to the platform storage and loading facility. A lease line is a type of flow line which carries all of the oil produced on a single lease to a storage tank.
  • Gathering and feeder lines. Gathering lines collect oil and gas from several locations for delivery to central accumulating points, such as from field crude oil tanks and gas plants to marine docks. Feeder lines collect oil and gas from several locations for delivery direct into trunk lines, such as moving crude oil from offshore platforms to onshore crude trunk pipelines. Gathering lines and feeder lines are typically larger in diameter than flow lines.
  • Crude trunk pipelines. Natural gas and crude oil are moved long distances from producing areas or marine docks to refineries and from refineries to storage and distribution facilities by 1- to 3-m- or larger-diameter trunk pipelines.
  • Petroleum product trunk pipelines. These pipelines move liquid petroleum products such as gasoline and fuel oil from refineries to terminals, and from marine and pipeline terminals to distribution terminals. Product pipelines may also distribute products from terminals to bulk plants and consumer storage facilities, and occasionally from refineries direct to consumers. Product pipelines are used to move LPG from refineries to distributor storage facilities or large industrial users.

 

Regulations and standards

Pipelines are constructed and operated to meet safety and environmental standards established by regulatory agencies and industry associations. Within the United States, the Department of Transportation (DOT) regulates the operation of pipelines, the Environmental Protection Agency (EPA) regulates spills and releases, the Occupational Safety and Health Administration (OSHA) promulgates standards covering worker health and safety, and the Interstate Commerce Commission (ICC) regulates common carrier pipelines. A number of industry organizations, such as the American Petroleum Institute and the American Gas Association, also publish recommended practices covering pipeline operations.

Pipeline construction

Pipeline routes are planned using topographic maps developed from aerial photogrammetric surveys, followed by actual ground surveying. After planning the route, obtaining right-of-way and permission to proceed, base camps are established and a means of access for construction equipment is required. Pipelines can be constructed working from one end to another or simultaneously in sections which are then connected.

The first step in laying pipeline is to construct a 15- to 30-m-wide service road along the planned route to provide a stable base for the pipe-laying and pipe-joining equipment and for underground pipeline excavation and backfill equipment. The pipe sections are laid on the ground alongside the service road. The ends of the pipe are cleaned, the pipe is bent horizontally or vertically, as necessary, and the sections are held in position by chocks above the ground and joined by multi-pass electrical arc-welding. The welds are checked visually and then with gamma radiation to assure that no defects are present. Each connected section is then coated with liquid soap and air-pressure tested to detect leaks.

The pipeline is cleaned, primed and coated with a hot, tar-like material to prevent corrosion and wrapped in an outer layer of heavy paper, mineral wool or plastic. If the pipe is to be buried, the bottom of the trench is prepared with a sand or gravel bed. The pipe may be weighed down by short, concrete sleeves to prevent its lifting out of the trench from groundwater pressure. After the underground pipeline is placed in the trench, the trench is backfilled and the surface of the ground returned to normal appearance. After coating and wrapping, aboveground piping is lifted up onto prepared stanchions or casements, which may have various design features such as anti-earthquake shock absorption. Pipelines may be insulated or have heat trace capabilities to keep products at desired temperatures throughout transport. All pipeline sections are hydrostatically tested prior to entering gas or liquid hydrocarbon service.

Pipeline operations

Pipelines may be either privately owned and operated, carrying only the owner’s products, or they may be common carriers, required to carry any company’s products provided that the pipeline’s product requirements and tariffs are met. The three major pipeline operations are pipeline control, pumping or compressor stations and delivery terminals. Storage, cleaning, communication and shipment are also important functions.

  • Pipeline control. Regardless of the product being transported, the size and length of the pipeline or the terrain, pipeline pumping stations, pressures and flow rates are completely controlled in order to ensure appropriate flow rates and continuous operations. Typically an operator and computer control the pumps, valves, regulators and compressors throughout the pipeline system from a central location.
  • Oil pumping and gas compressor stations. Crude oil and petroleum products pumping stations and gas compressor stations are located at wellheads and along the pipeline route as needed to maintain pressure and volume. Pumps are driven by electric motors or diesel engines, and turbines may be powered by fuel oil, gas or steam. Many of these stations are automatically controlled and not staffed at most times. Pumps, with and without vapour return lines or pressure equalizing lines, are commonly used in smaller pipelines for transport of LNG, LPG and compressed natural gas (CNG). Pressure drop detectors are installed to signal any leaks in pipelines, and excess flow valves or other flow limiting devices are used to minimize the rate of flow in case of a pipeline leak. Storage vessels and reservoirs may be isolated from main pipelines by manually operated or remote control valves or fusible link valves.
  • Pipeline product storage. Crude and petroleum product pipeline terminals have breakout storage tanks to which shipments may be diverted, where they are held until required by a refinery, terminal or user (see figure 1). Other tanks at pipeline pumping stations contain fuel for operating diesel-driven pump motors or for running electrical generators. Because gas fields produce continuously and gas pipelines operate continuously, during times of reduced demand, such as summertime, liquefied natural and petroleum gases are stored underground in natural caverns or salt domes until needed.
  • Pipeline cleaning. Pipelines are cleaned on a scheduled basis or as necessary in order to continue flow by reducing friction and maintaining as large a diameter interior as possible. A special cleaning device, called a pig or go-devil, is placed into the pipeline and pushed along by the flow of oil from one pumping station to the next. As the pig passes through the pipeline it scrapes off any dirt, wax or other deposits which have built up inside the pipeline walls. When it reaches a pumping station, the pig is removed, cleaned and reinserted into the pipeline to travel to the next station.
  • Communications. It is important that there be communication and agreement concerning schedules, pumping rates and pressures and emergency procedures between pipeline stations and operators and those shipping and receiving crude oil, gas and petroleum products. Some pipeline companies have private telephone systems which transmit the signal along the pipeline, while others use radios or public telephones. Many pipelines use ultra-high-frequency microwave transmitter systems for computer communications between control centres and pumping stations.
  • Petroleum product shipment. Petroleum products may be shipped a number of different ways on pipelines. A company operating a refinery may blend a specific grade of its own gasoline with appropriate additives (additize) and ship a batch through a pipeline directly to its own terminal for distribution to its customers. Another method is for a refinery to produce a batch of gasoline, called a frangible or specification product, which is blended to meet a common carrier pipeline company’s product specifications. The gasoline is placed into the pipeline for delivery to any company’s terminals which are connected to the pipeline system. In a third method, products are shipped by companies to each other’s terminals and exchanged in order to avoid extra transportation and handling. Frangible and exchange products are usually blended and additized at the terminal which receives the product from the pipeline, to meet the specific requirements of each company operating from the terminal. Finally, some products are delivered by pipeline from terminals and refineries direct to large commercial consumers—jet fuel to airports, gas to gas distribution companies and fuel oil to electric generating plants.
  • Product receipt and delivery. Pipeline operators and terminal operators should jointly establish programmes to provide for the safe receipt and transfer of products and to coordinate actions in case an emergency occurs on the pipeline or at the terminal during shipment which requires shutdown or diversion of product.

 

Figure 1. A terminal operator transfers product the Pasagoula Refinery into holding tanks in the Deraville Terminal near Atlanta, Georgia, US.

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American Petroleum Institute

Instructions for receiving pipeline deliveries should include verification of the availability of the storage tanks to hold the shipment, opening and aligning tank and terminal valves in anticipation of delivery, checking to assure that the proper tank is receiving product immediately after the start of delivery, conducting required sampling and testing of batches at the start of delivery, performing batch changes and tank switches as required, monitoring receipts to assure that overfills do not occur and maintaining communications between the pipeline and the terminal. The use of written communications between terminal workers, especially when shift changes occur during product transfer, should be considered.

Batch shipments and interface

Although pipelines originally were used to move only crude oil, they evolved into carrying all types and different grades of liquid petroleum products. Because petroleum products are transported in pipelines by batches, in succession, there is commingling or mixing of the products at the interfaces. The product intermix is controlled by one of three methods: downgrading (derating), using liquid and solid spacers for separation or reprocessing the intermix. Radioactive tracers, colour dyes and spacers may be placed into the pipeline to identify where the interfaces occur. Radioactive sensors, visual observation or gravity tests are conducted at the receiving facility to identify different pipeline batches.

Petroleum products are normally transported through pipelines in batch sequences with compatible crude oils or products adjoining one another. One method of maintaining product quality and integrity, downgrading or derating, is accomplished by lowering the interface between the two batches to the level of the least affected product. For example, a batch of high-octane premium gasoline is typically shipped immediately before or after a batch of lower-octane regular gasoline. The small quantity of the two products which has intermixed will be downgraded to the lower octane rating regular gasoline. When shipping gasoline before or after diesel fuel, a small amount of diesel interface is allowed to blend into the gasoline, rather than blending gasoline into the diesel fuel, which could lower its flashpoint. Batch interfaces are typically detected by visual observation, gravitometers or sampling.

Liquid and solid spacers or cleaning pigs may be used to physically separate and identify different batches of products. The solid spacers are detected by a radioactive signal and diverted from the pipeline into a special receiver at the terminal when the batch changes from one product to another. Liquid separators may be water or another product that does not commingle with either of the batches it is separating and is later removed and reprocessed. Kerosene, which is downgraded (derated) to another product in storage or is recycled, can also be used to separate batches.

A third method of controlling the interface, often used at the refinery ends of pipelines, is to return the interface to be reprocessed. Products and interfaces which have been contaminated with water may also be returned for reprocessing.

Environmental protection

Because of the large volumes of products which are transported by pipelines on a continuous basis, there is opportunity for environmental damage from releases. Depending on company and regulatory safety requirements and the pipeline’s construction, location, weather, accessibility and operation, a considerable amount of product may be released should a break in the line or leak occur. Pipeline operators should have emergency response and spill contingency plans prepared and have containment and clean-up materials, personnel and equipment available or on call. Simple field solutions such as building earth dykes and drainage ditches can be quickly implemented by trained operators to contain and divert spilled product.

Maintaining pipelines and worker health and safety

The first pipelines were made of cast iron. Modern trunk pipelines are constructed of welded, high-strength steel, which can withstand high pressures. Pipe walls are periodically tested for thickness to determine whether internal corrosion or deposits have occurred. Welds are checked visually and with gamma radiation to assure that no defects are present.

Plastic pipe may be used for low-pressure, small-diameter flow lines and gathering lines in gas and crude-oil-producing fields, since plastic is light in weight and easy to handle, assemble and move.

When a pipeline is separated by cutting, spreading flanges, removing a valve or opening the line, an electrostatic arc may be created by impressed cathodic protection voltage, corrosion, sacrificial anodes, nearby high-voltage power lines or stray ground currents. This should be minimized by grounding (earthing) the pipe, de-energizing the cathodic rectifiers closest to both sides of the separation and connecting a bonding cable to each side of the piping prior to starting work. As additional pipeline sections, valves and so on are added to an existing line, or during construction, they should first be bonded to the pipelines in place.

Work on pipelines should cease during electrical storms. Equipment used to lift and place pipe should not be operated within 3 m of high-voltage electric lines. Any vehicles or equipment working in the vicinity of high-voltage lines should have trailing grounding straps attached to the frames. Temporary metal buildings should also be grounded.

Pipelines are specially coated and wrapped to prevent corrosion. Cathodic electrical protection may also be required. After the pipeline sections are coated and insulated, they are joined by special clamps connected to metallic anodes. The pipeline is subjected to a grounded source of direct current of sufficient capacity so that the pipeline acts as a cathode and does not corrode.

All pipeline sections are hydrostatically tested prior to entering gas or liquid hydrocarbon service and, depending on regulatory and company requirements, at regular intervals during the life of the pipeline. Air must be eliminated from pipelines prior to hydrostatic testing, and hydrostatic pressure built up and reduced at safe rates. Pipelines are regularly patrolled, usually by aerial surveillance, to visually detect leaks, or monitored from the control centre to detect a drop in flow rate or pressure, which would signify that a break in the pipeline has occurred.

Pipeline systems are provided with warning and signalling systems to alert operators so they may take corrective action in an emergency. Pipelines may have automatic shutdown systems which activate emergency pressure valves upon sensing increased or reduced pipeline pressure. Manually or automatically operated isolation valves are typically located at strategic intervals along pipelines, such as at pumping stations and at both sides of river crossings.

An important consideration when operating pipelines is to provide a means of warning contractors and others who may be working or conducting excavations along the pipeline route, so that the pipeline is not inadvertently ruptured, breached or punctured, resulting in a vapour or gas explosion and fire. This is usually done by regulations which require construction permits or by pipeline companies and associations providing a central number which contractors can call prior to excavation.

Because crude oil and flammable petroleum products are transported in pipelines, the possibility exists for fire or explosion in case of a line break or release of vapour or liquid. Pressure should be reduced to a safe level before working on high-pressure pipelines. Combustible gas testing should be conducted and a permit issued prior to repair or maintenance involving hot work or hot tapping on pipelines. The pipeline should be cleared of flammable liquids and vapours or gas prior to starting work. If a pipeline cannot be cleared and an approved plug is used, safe work procedures should be established and followed by qualified workers. The line should be vented a safe distance from the hot work area to relieve any build-up of pressure behind the plug.

Proper safety procedures should be established and followed by qualified workers when hot tapping pipelines. If welding or hot tapping is conducted in an area where a spill or leak has occurred, the outside of the pipe should be cleaned of liquid, and contaminated soil should be removed or covered to prevent ignition.

It is very important to notify operators at the nearest pumping stations on each side of the operating pipeline where maintenance or repair is to be performed, in case shutdown is required. When crude oil or gas is being pumped into pipelines by producers, the pipeline operators must provide specific instructions to the producers as to actions to take during repair, maintenance or in an emergency. For example, prior to tie-in of production tanks and lines to pipelines, all gate valves and bleeders for the tanks and lines involved in the tie-in should be closed and locked or sealed until the operation is completed.

Normal safety precautions concerning pipe and materials handling, toxic and hazardous exposures, welding and excavation apply during pipeline construction. Workers clearing right-of-way should protect themselves from climatic conditions; poisonous plants, insects and snakes; falling trees and rocks; and so on. Excavations and trenches should be sloped or shored to prevent collapse during underground pipeline construction or repair (see the article “Trenching” in the chapter Construction). Workers should follow safe work practices when opening and de-energizing electrical transformers and switches.

Pipeline operating and maintenance personnel often work alone and are responsible for long stretches of pipeline. Atmospheric testing and the use of personal and respiratory protective equipment is needed to determine oxygen and flammable vapour levels and protect against toxic exposures to hydrogen sulphide and benzene when gauging tanks, opening lines, cleaning spills, sampling and testing, shipping, receiving and performing other pipeline activities. Workers should wear dosimeters or film badges and avoid exposure when working with density gauges, source holders or other radioactive materials. The use of personal and respiratory protective equipment should be considered for exposure to burns from the hot protective tar used in pipe-coating operations and from toxic vapours which contain polynuclear aromatic hydrocarbons.

Marine Tankers and Barges

The majority of the world’s crude oil is transported by tankers from producing areas such as the Middle East and Africa to refineries in consumer areas such as Europe, Japan and the United States. Oil products were originally transported in large barrels on cargo ships. The first tanker ship, which was built in 1886, carried about 2,300 SDWT (2,240 pounds per ton) of oil. Today’s supertankers can be over 300 m long and carry almost 200 times as much oil (see figure 2). Gathering and feeder pipelines often end at marine terminals or offshore platform loading facilities, where the crude oil is loaded into tankers or barges for transport to crude trunk pipelines or refineries. Petroleum products also are transported from refineries to distribution terminals by tanker and barge. After delivering their cargoes, the vessels return in ballast to loading facilities to repeat the sequence.

Figure 2. SS Paul L. Fahrney oil tanker.

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American Petroleum Institute

Liquefied natural gas is shipped as a cryogenic gas in specialized marine vessels with heavily insulated compartments or reservoirs (see figure 3). At the delivery port, the LNG is off-loaded to storage facilities or regasification plants. Liquefied petroleum gas may be shipped both as a liquid in uninsulated marine vessels and barges and as a cryogenic in insulated marine vessels. Additionally, LPG in containers (bottled gas) may be shipped as cargo on marine vessels and barges.

Figure 3. LNG Leo tanker loading at Arun, Sumatra, Indonesia.

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American Petroleum Institute

LPG and LNG marine vessels

The three types of marine vessels used for transport of LPG and LNG are:

  • vessels with reservoirs pressurized up to 2 mPa (LPG only)
  • vessels with heat-insulated reservoirs and a reduced pressure of 0.3 to 0.6 mPa (LPG only)
  • cryogenic vessels with heat-insulated reservoirs pressurized close to atmospheric pressure (LPG and LNG).

 

Shipment of LHGs on marine vessels requires constant safety awareness. Transfer hoses must be suitable for the correct temperatures and pressures of the LHGs being handled. To prevent a flammable mixture of gas vapour and air, inert gas (nitrogen) blanketing is provided around reservoirs, and the area is continually monitored to detect leaks. Before loading, storage reservoirs should be inspected to ensure that they are free of contaminants. If reservoirs contain inert gas or air, they should be purged with LHG vapour prior to loading the LHG. Reservoirs should be constantly inspected to ensure integrity, and safety valves should be installed to relieve the LHG vapour generated at maximum heat load. Marine vessels are provided with fire suppression systems and have comprehensive emergency response procedures in place.

Crude oil and petroleum products marine vessels

Oil tankers and barges are vessels designed with the engines and quarters at the rear of the vessel and the remainder of the vessel divided into special compartments (tanks) to carry crude oil and liquid petroleum products in bulk. Cargo pumps are located in pump rooms, and forced ventilation and inerting systems are provided to reduce the risk of fires and explosions in pump rooms and cargo compartments. Modern oil tankers and barges are built with double hulls and other protective and safety features required by the United States Oil Pollution Act of 1990 and the International Maritime Organization (IMO) tanker safety standards. Some new ship designs extend double hulls up the sides of the tankers to provide additional protection. Generally, large tankers carry crude oil and small tankers and barges carry petroleum products.

  • Supertankers. Ultra-large and very large crude carriers (ULCCs and VLCCs) are restricted by their size and draft to specific routes of travel. ULCCs are vessels whose capacity is over 300,000 SDWTs, and VLCCs have capacities ranging from 160,000 to 300,000 SDWTs. Most large crude carriers are not owned by oil companies, but are chartered from transportation companies which specialize in operating these super-sized vessels.
  • Oil tankers. Oil tankers are smaller than VLCCs, and, in addition to ocean travel, they can navigate restricted passages such as the Suez and Panama Canals, shallow coastal waters and estuaries. Large oil tankers, which range from 25,000 to 160,000 SDWTs, usually carry crude oil or heavy residual products. Smaller oil tankers, under 25,000 SDWT, usually carry gasoline, fuel oils and lubricants.
  • Barges. Barges operate mainly in coastal and inland waterways and rivers, alone or in groups of two or more, and are either self-propelled or moved by tugboat. They may carry crude oil to refineries, but more often are used as an inexpensive means of transporting petroleum products from refineries to distribution terminals. Barges are also used to off-load cargo from tankers offshore whose draft or size does not allow them to come to the dock.

 

Barge and ship loading and unloading

Vessel-to-shore procedures, safety checklists and guidelines should be established and agreed upon by terminal and marine vessel operators. The International Safety Guide for Oil Tankers and Terminals (International Chamber of Shipping 1978) contains information and samples of checklists, guidelines, permits and other procedures covering safe operations when loading or unloading vessels, which may be used by vessel and terminal operators.

Although marine vessels sit in water and are thereby intrinsically grounded, there is a need to provide protection from static electricity which can build up during loading or unloading. This is accomplished by bonding or connecting metal objects on the dock or loading/unloading apparatus to the metal of the vessel. Bonding is also accomplished by use of conductive loading hose or piping. An electrostatic spark of ignitable intensity may also be generated when lowering equipment, thermometers or gauging devices into compartments immediately after loading; enough time must be allowed for the static charge to dissipate.

Ship-to-shore electric currents, which are different from static electricity, may be generated by cathodic protection of the vessel’s hull or dock, or by galvanic potential differences between the vessel and the shore. These currents also build up in metal loading/unloading apparatus. Insulating flanges may be installed within the length of the loading arm and at the point where flexible hoses connect to the shore pipeline system. When the connections are broken, there is no opportunity for a spark to jump from one metal surface to another.

All vessels and terminals need mutually agreed upon emergency response procedures in case of a fire or release of product, vapour or toxic gas. These must cover emergency operations, stopping product flow and emergency removal of a vessel from the dock. The plans should consider communications, fire-fighting, vapour cloud mitigation, mutual aid, rescue, clean-up and remediation measures.

Fire protection portable equipment and fixed systems should be in accord with government and company requirements and appropriate to the size, function, exposure potential and value of the dock and wharf facilities. The International Safety Guide for Oil Tankers and Terminals (International Chamber of Shipping 1978) contains a sample fire notice which may be used as a guide by terminals for dock fire prevention.

Marine vessel health and safety

In addition to the usual maritime working hazards, transporting crude oil and flammable liquids by marine vessel creates a number of special health, safety and fire prevention situations. These include surging and expansion of liquid cargo, flammable vapour hazards during transport and when loading and unloading, possibility of pyrophoric ignition, toxic exposures to materials such as hydrogen sulphide and benzene and safety considerations when venting, flushing and cleaning compart-ments. The economics of operating modern tankers requires them to be at sea for extended periods of time with only short intervals in port to load or unload cargo. This, together with the fact that tankers are highly automated, creates unique mental and physical demands on the few crew members used to operate the vessels.

Fire and explosion protection

Emergency plans and procedures should be developed and implemented that are appropriate for the type of cargo on board and other potential hazards. Fire-fighting equipment must be supplied. Response team members who have shipboard fire-fighting, rescue and spill clean-up responsibilities should be trained, drilled and equipped to handle potential emergencies. Water, foam, dry chemicals, halon, carbon dioxide and steam are used as cooling, inhibiting and smothering fire-fighting agents aboard marine vessels, although halon is being phased out due to environmental concerns. The requirements for vessel fire-fighting equipment and systems are established by the country under whose flag the vessel sails and by company policy, but usually follow the recommendations of the 1974 International Convention for the Safety of Life at Sea (SOLAS).

Strict control of flames or naked lights, lighted smoking materials and other sources of ignition, such as welding or grinding sparks, electrical equipment and unprotected light bulbs, is required on vessels at all times to reduce the risk of fire and explosion. Prior to conducting hot work on board marine vessels, the area should be examined and tested to assure that conditions are safe, and permits should be issued for each specific task allowed.

One method of preventing explosions and fires in the vapour space of cargo compartments is to maintain the level of oxygen below 11% by making the atmosphere inert with a noncombustible gas. Sources for inert gas are exhaust gases from the vessel’s boilers or an independent gas generator or a gas turbine fitted with an afterburner. The 1974 SOLAS Convention implies that vessels carrying cargo with flashpoints below 60°C should have compartments fitted with inert systems. Vessels using inert gas systems should maintain cargo compartments in non-flammable conditions at all times. Inert gas compartments should be constantly monitored to assure safe conditions and should not be allowed to become flammable, because of the danger of ignition from pyrophoric deposits.

Confined spaces

Confined spaces on marine vessels, such as cargo compartments, paint lockers, pump rooms, fuel tanks and spaces between double hulls, must be treated the same as any confined space for entry, hot work and cold work. Tests for oxygen content, flammable vapours and toxic substances, in that order, must be conducted prior to entering confined spaces. A permit system should be established and followed for all confined space entry, safe (cold) work and hot work, which indicates safe exposure levels and required personal and respiratory protective equipment. In waters of the United States, these tests may be conducted by qualified individuals called “marine chemists”.

Compartments on marine vessels such as cargo tanks and pump rooms are confined spaces; when cleaning those which have been made inert or have flammable vapour, toxic or unknown atmospheres, they should be tested, and special safety and respiratory protection procedures should be followed. After crude oil has been unloaded, a small amount of residue, called clingage, remains on the interior surfaces of the compartments, which may then be washed and filled with water for ballast. One method of reducing the amount of residue is to install fixed equipment which removes up to 80% of the clingage by washing down the sides of inerted compartments with crude oil during unloading.

Pumps, valves and equipment

A work permit should be issued and safe work procedures followed, such as bonding, draining and vapour freeing, flammable vapour and toxic exposure testing, and providing stand-by fire protection equipment when operations, maintenance or repair requires opening cargo pumps, lines, valves or equipment on board marine vessels.

Toxic exposures

There is an opportunity for vented gases such as flue gas or hydrogen sulphide to reach the decks of vessels, even from specially designed vent systems. Testing should be continuously conducted to determine inert gas levels on all vessels and hydrogen sulphide levels on vessels which contain or previously carried sour crude oil or residual fuel. Tests should be conducted for benzene exposure on vessels carrying crude oil and gasoline. Inert gas scrubber effluent water and condensate water is acidic and corrosive; PPE should be used when contact is possible.

Environmental protection

Marine vessels and terminals should establish procedures and provide equipment to protect the environment from spills on water and land, and from releases of vapour to the air. The use of large vapour recovery systems at marine terminals is growing. Care must be taken to comply with air pollution requirements when vessels vent compartments and enclosed spaces. Emergency response procedures should be established, and equipment and trained personnel should be available to respond to spills and releases of crude oil and flammable and combustible liquids. A responsible person should be designated to ensure that notifications are made to both the company and the appropriate authorities should a reportable spill or release occur.

In the past, the oil-contaminated ballast water and tank washings were flushed out of the compartments at sea. In 1973, the International Convention for Prevention of Pollution from Ships established requirements that before the water is discharged at sea, the oily residue must be separated and retained on board for eventual onshore processing. Modern tankers have segregated ballast systems, with different lines, pumps and tanks than those used for cargo (in accordance with international recommen-dations), so that there is no possibility of contamination. Older vessels still carry ballast in cargo tanks, so special procedures, such as pumping oily water into designated onshore tanks and processing facilities, must be followed when discharging ballast in order to prevent pollution.

Motor Vehicle and Railroad Transport of Petroleum Products

Crude oil and petroleum products were initially transported by horse-drawn tank wagons, then by railroad tank cars and finally by motor vehicles. Following receipt at terminals from marine vessels or pipelines, bulk liquid petroleum products are delivered by non-pressure tank trucks or rail tank cars directly to service stations and consumers or to smaller terminals, called bulk plants, for redistribution. LPG, gasoline anti-knock compounds, hydrofluoric acid and many other products, chemicals and additives used in the oil and gas industry are transported in pressure tank cars and tank trucks. Crude oil may also be transported by tank truck from small producing wells to gathering tanks, and by tank truck and railroad tank car from storage tanks to refineries or main pipelines. Packaged petroleum products in bulk bins or drums and pallets and cases of smaller containers are carried by package truck or railroad box car.

Government regulations

Transportation of petroleum products by motor vehicle or railroad tank car is regulated by government agencies throughout most of the world. Agencies such as the US DOT and the Canadian Transport Commission (CTC) have established regulations governing the design, construction, safety devices, testing, preventive maintenance, inspection and operation of tank trucks and tank cars. Regulations governing railroad tank car and tank truck operations typically include tank pressure and pressure relief device testing and certification before being placed into initial service and at regular intervals thereafter. The Association of American Railroads and the National Fire Protection Association (NFPA) are typical of organizations which publish specifications and requirements for the safe operation of tank cars and tank trucks. Most governments have regulations or adhere to United Nations Conventions which require the identification of and information concerning hazardous materials and petroleum products which are shipped in bulk or in containers. Railroad tank cars, tank trucks and package trucks are placarded to identify any hazardous products being transported and to provide emergency response information.

Railroad tank cars

Railroad tank cars are constructed of carbon steel or aluminium and may be pressurized or unpressurized. Modern tank cars can hold up to 171,000 l of compressed gas at pressures up to 600 psi (1.6 to 1.8 mPa). Non-pressure tank cars have evolved from small wooden tank cars of the late 1800s to jumbo tank cars which transport as much as 1.31 million litres of product at pressures up to 100 psi (0.6 mPa). Non-pressure tank cars may be individual units with one or multiple compartments or a string of interconnected tank cars, called a tank train. Tank cars are loaded individually, and entire tank trains can be loaded and unloaded from a single point. Both pressure and non-pressure tank cars may be heated, cooled, insulated and thermally protected against fire, depending on their service and the products transported.

All railroad tank cars have top- or bottom-liquid or vapour valves for loading and unloading and hatch entries for cleaning. They are also equipped with devices intended to prevent the increase of internal pressure when exposed to abnormal con-ditions. These devices include safety relief valves held in place by a spring which can open to relieve pressure and then close; safety vents with rupture discs that burst open to relieve pressure but cannot reclose; or a combination of the two devices. A vacuum relief valve is provided for non-pressure tank cars to prevent vacuum formation when unloading from the bottom. Both pressure and non-pressure tank cars have protective housings on top surrounding the loading connections, sample lines, thermometer wells and gauging devices. Platforms for loaders may or may not be provided on top of cars. Older non-pressure tank cars may have one or more expansion domes. Fittings are provided on the bottom of tank cars for unloading or cleaning. Head shields are provided on the ends of tank cars to prevent puncture of the shell by the coupler of another car during derailments.

LNG is shipped as a cryogenic gas in insulated tank truck and rail pressure tank cars. Pressure tank trucks and rail tank cars for LNG transport have a stainless steel inner reservoir suspended in an outer reservoir of carbon steel. The annular space is a vacuum filled with insulation to maintain low temperatures during shipment. To prevent gas from igniting back to the tanks, they are equipped with two independent, remotely controlled fail-safe emergency shut-off valves on the filling and discharge lines and have gauges on both the inside and outside reservoirs.

LPG is transported on land in specially designed rail tank cars (up to 130 m3 capacity) or tank trucks (up to 40 m3 capacity). Tank trucks and rail tank cars for LPG transport are typically uninsulated steel cylinders with spherical bottoms, equipped with gauges, thermometers, two safety relief valves, a gas level meter and maximum fill indicator and baffles.

Rail tank cars transporting LNG or LPG should not be overloaded, since they may sit on a siding for some period of time and be exposed to high ambient temperatures, which could cause overpressure and venting. Bond wires and grounding cables are provided at rail and tank truck loading racks to help neutralize and dissipate static electricity. They should be connected before operations commence and not disconnected until operations are complete and all valves are closed. Truck and rail loading facilities are typically protected by fire water spray or mist systems and fire extinguishers.

Tank trucks

Petroleum products and crude oil tank trucks are typically constructed of carbon steel, aluminium or a plasticized fibreglass material, and vary in size from 1,900-l tank wagons to jumbo 53,200-l tankers. The capacity of tank trucks is governed by regulatory agencies, and usually is dependent upon highway and bridge capacity limitations and the allowable weight per axle or total amount of product allowed.

There are pressurized and non-pressurized tank trucks, which may be non-insulated or insulated depending on their service and the products transported. Pressurized tank trucks are usually single compartment, and non-pressurized tank trucks may have single or multiple compartments. Regardless of the number of compartments on a tank truck, each compartment must be treated individually, with its own loading, unloading and safety-relief devices. Compartments may be separated by single or double walls. Regulations may require that incompatible products and flammable and combustible liquids carried in different compartments on the same vehicle be separated by double walls. When pressure testing compartments, the space between the walls should also be tested for liquid or vapour.

Tank trucks have either hatches which open for top loading, valves for closed top- or bottom-loading and unloading, or both. All compartments have hatch entries for cleaning and are equipped with safety relief devices to mitigate internal pressure when exposed to abnormal conditions. These devices include safety relief valves held in place by a spring which can open to relieve pressure and then close, hatches on non-pressure tanks which pop open if the relief valves fail and rupture discs on pressurized tank trucks. A vacuum relief valve is provided for each non-pressurized tank truck compartment to prevent vacuum when unloading from the bottom. Non-pressurized tank trucks have railings on top to protect the hatches, relief valves and vapour recovery system in case of a rollover. Tank trucks are usually equipped with breakaway, self-closing devices installed on compartment bottom loading and unloading pipes and fittings to prevent spills in case of damage in a rollover or collision.

Rail tank car and tank truck loading and unloading

While railroad tank cars are almost always loaded and unloaded by workers assigned to these specific duties, tank trucks may be loaded and unloaded by either loaders or drivers. Tank cars and tank trucks are loaded at facilities called loading racks, and may be top loaded through open hatches or closed connections, bottom loaded through closed connections, or a combination of both.

Loading

Workers who load and unload crude oil, LPG, petroleum products, and acids and additives used in the oil and gas industry, should have a basic understanding of the characteristics of the products handled, their hazards and exposures and the operating procedures and work practices needed to perform the job safely. Many government agencies and companies require the use and completion of inspection forms upon receipt and shipment and prior to loading and unloading railroad tank cars and tank trucks. Tank trucks and railroad tank cars may be loaded through open hatches on the top or through fittings and valves at the top or bottom of each tank or compartment. Closed connections are required when pressure loading and where vapour recovery systems are provided. If loading systems do not activate for any reason (such as improper operation of the vapour recovery system or a fault in the grounding or bonding system), by-pass should not be attempted without approval. All hatches should be closed and securely latched during transit.

Workers should follow safe work practices to avoid slips and falls when top loading. If loading controls use pre-set meters, loaders must be careful to load the correct products into the assigned tanks and compartments. All compartment hatches should be shut when bottom loading, and when top loading, only the compartment being loaded should be open. When top loading, splash loading should be avoided by placing the loading tube or hose close to the bottom of the compartment and starting to load slowly until the opening is submerged. During manual top loading operations, loaders should remain in attendance, not tie down the loading shut-off (deadman) control and not overfill the compartment. Loaders should avoid exposures to product and vapour by standing upwind and averting the head when top loading through open hatches and by wearing protective equipment when handling additives, obtaining samples and draining hoses. Loaders should be aware of and follow prescribed response actions in case of a hose or line rupture, spill, release, fire or other emergency.

Unloading and delivery

When unloading tank cars and tank trucks, it is important first to assure that each product is unloaded into the proper designated storage tank and that the tank has sufficient capacity to hold all of the product being delivered. Although valves, fill pipes, lines and fill covers should be colour coded or otherwise marked to identify the product contained, the driver should still be responsible for product quality during delivery. Any misdelivery of product, mixing or contamination should be immediately reported to the recipient and to the company to prevent serious consequences. When drivers or operators are required to additize products or obtain samples from storage tanks following delivery to assure product quality or for any other reason, all safety and health provisions specific to the exposure should be followed. Persons engaged in delivery and unloading operations should remain in the vicinity at all times and know what to do in an emergency, including notification, stopping product flow, cleaning spills and when to leave the area.

Pressurized tanks may be unloaded by compressor or pump, and unpressurized tanks by gravity, vehicle pump or recipient pump. Tank trucks and tank cars which carry lubrication or industrial oils, additives and acids are sometimes unloaded by pressurizing the tank with an inert gas such as nitrogen. Tank cars or tank trucks may need to be heated using steam or electric coils in order to unload heavy crude oils, viscous products and waxes. All of these activities have inherent dangers and exposures. Where required by regulation, unloading should not commence until the vapour recovery hoses have been connected between the delivery tank and the storage tank. When delivering petroleum products to residences, farms and commercial accounts, drivers should gauge any tank which is not equipped with a vent alarm in order to prevent an overfill.

Loading-rack fire protection

Fires and explosions at top and bottom tank car and tank truck loading racks may occur from causes such as electrostatic build-up and incendiary spark discharge in a flammable atmosphere, unauthorized hot work, flashback from a vapour recovery unit, smoking or other unsafe practices.

Sources of ignition, such as smoking, running internal combustion engines and hot work activity, should be controlled at the loading rack at all times, and particularly during loading or other operations when a spill or release may occur. Loading racks may be equipped with portable fire extinguishers and manually or automatically operated foam, water or dry chemical fire extinguishing systems. If vapour recovery systems are in use, flame arrestors should be provided to prevent flashback from the recovery unit to the loading rack.

Drainage should be provided at loading racks to divert product spills away from the loader, tank truck or tank car and the loading rack pad. Drains should be provided with fire traps to prevent migration of flames and vapours through sewer systems. Other loading-rack safety considerations include emergency shut-down controls placed at loading spots and other strategic locations in the terminal and automatic pressure-sensing valves which stop product flow to the rack in case of a leak in the product lines. Some companies have installed automatic brake lock systems on their tank truck fill connections, which lock the brakes and will not allow the truck to be moved from the rack until the fill lines have been disconnected.

Electrostatic ignition hazards

Some products such as intermediate distillates and low-vapour-pressure fuels and solvents tend to accumulate electrostatic charges. When loading tank cars and tank trucks, there is always an opportunity for electrostatic charges to be generated by friction as product goes through lines and filters and by splash loading. This can be mitigated by designing loading racks to allow for relaxation time in piping downstream from pumps and filters. Compartments should be checked to assure that they do not contain any unbonded or floating objects which could act as static accumulators. Bottom loaded compartments may be provided with internal cables to help dissipate electrostatic charges. Sample containers, thermometers or other items should not be lowered into compartments until a waiting period of at least 1 minute has elapsed, to allow any electrostatic charge which has accumulated in the product to dissipate.

Bonding and grounding are important considerations in dissipating electrostatic charges which build up during loading operations. By keeping the fill pipe in contact with the metal side of the hatch when top loading, and through the use of metal loading arms or conductive hose when loading through closed connections, the tank truck or tank car is bonded to the loading rack, maintaining the same electrical charge between the objects so that a spark is not created when the loading tube or hose is removed. The tank car or tank truck may also be bonded to the loading rack by use of a bonding cable, which carries any accumulated charge from a terminal on the tank to the rack, where it is then grounded by a grounding cable and rod. Similar bonding precautions are needed when unloading from tank cars and tank trucks. Some loading racks are provided with electronic connectors and sensors which will not allow loading pumps to activate until a positive bond is achieved.

During cleaning, maintenance or repair, pressurized LPG tank cars or tank trucks are usually opened to the atmosphere, allowing air to enter the tank. In order to prevent combustion from electrostatic charges when loading these cars for the first time after such activities, it is necessary to reduce the oxygen level below 9.5% by blanketing the tank with inert gas, such as nitrogen. Precautions are needed to prevent liquid nitrogen from entering the tank if the nitrogen is provided from portable containers.

Switch loading

Switch loading occurs when intermediate- or low-vapour-pressure products such as diesel fuel or fuel oil are loaded into a tank car or tank truck compartment which previously contained a flammable product such as gasoline. The electrostatic charge generated during loading can discharge in an atmosphere which is within the flammable range, with a resultant explosion and fire. This hazard can be controlled when top loading by lowering the fill tube to the bottom of the compartment and loading slowly until the end of the tube is submerged to avoid splash loading or agitation. Metal to metal contact should be maintained during loading in order to provide a positive bond between the loading tube and the tank hatchway. When bottom loading, initial slow fill or splash deflectors are used to reduce static build-up. Prior to switch loading, tanks which cannot be drained dry may be flushed out with a small amount of the product to be loaded, to remove any flammable residue in sumps, lines, valves and onboard pumps.

Shipping products by rail box cars and package vans

Petroleum products are shipped by motor truck package vans and railroad box cars in metal, fibre and plastic containers of various sizes, from 55-gallon (209-l) drums to 5-gallon (19-l) pails and from 2-1/2-gallon (9.5-l) to 1-quart (.95-l) containers, in corrugated boxes, usually on pallets. Many industrial and commercial petroleum products are shipped in large metal, plastic or combination intermediate bulk containers ranging in size from 380 to over 2,660 l capacity. LPG is shipped in large and small pressure containers. In addition, samples of crude oil, finished products and used products are shipped by mail or express freight carrier to laboratories for assay and analysis.

All of these products, containers and packages have to be handled in accordance with government regulations for hazardous chemicals, flammable and combustible liquids and toxic materials. This requires the use of hazardous materials manifests, shipping documents, permits, receipts and other regulatory requirements, such as marking the outsides of packages, containers, motor trucks and box cars with proper identification and a hazard warning label. Proper utilization of tank trucks and tank cars is important to the petroleum industry. Because storage capacity is finite, delivery schedules need to be met, from the delivery of crude oil to keep refineries running to the delivery of gasoline to service stations, and from the delivery of lubricants to commercial and industrial accounts to the delivery of heating oil to homes.

LPG is supplied to consumers by bulk tank trucks which pump directly into smaller onsite storage tanks, both above ground and below ground (e.g., service stations, farms, commercial and industrial consumers). LPG is also delivered to consumers by truck or van in containers (gas cylinders or bottles). LNG is delivered in special cryogenic containers which have an inner fuel tank surrounded by insulation and an outer shell. Similar containers are provided for vehicles and appliances which use LNG as a fuel. Compressed natural gas is normally delivered in conventional compressed gas cylinders, such as those used on industrial lift trucks.

In addition to the normal safety and health precautions required in rail car and package trucking operations, such as moving and handling heavy objects and operating industrial trucks, workers should be familiar with the hazards of the products they are handling and delivering, and know what to do in case of a spill, release or other emergency. For example, intermediate bulk containers and drums should not be dropped out of box cars or from the tailgates of trucks onto the ground. Both companies and government agencies have established special regulations and requirements for drivers and operators who are involved in the transport and delivery of flammable and hazardous petroleum products.

Tank truck and package van drivers often work alone and may have to travel great distances for a number of days to deliver their loads. They work both day and night and in all sorts of weather conditions. Manoeuvring super-sized tank trucks into service stations and customer locations without hitting parked vehicles or fixed objects requires patience, skill and experience. Drivers should have the physical and mental characteristics required for this work.

Driving tank trucks is different from driving package vans in that the liquid product tends to shift forward as the truck stops, backwards as the truck accelerates and from side to side as the truck turns. Tank truck compartments should be fitted with baffles which restrict the movement of product during transport. Considerable skill is required by drivers to overcome the inertia created by this phenomenon, called “mass in motion”. Occasionally, tank truck drivers are required to pump out storage tanks. This activity requires special equipment, including suction hose and transfer pumps, and safety precautions, such as bonding and grounding to dissipate electrostatic build-up and to prevent any release of vapours or liquids.

Motor vehicle and rail car emergency response

Drivers and operators should be familiar with notification requirements and emergency response actions in case of a fire or a release of product, gas or vapour. Product identification and hazard warning placards in compliance with industry, association or national marking standards are posted on trucks and rail cars to allow emergency responders to determine the precautions needed in case of a spill or release of vapour, gas or product. Motor vehicle drivers and train operators may also be required to carry material safety data sheets (MSDSs) or other documentation describing the hazards and precautions for handling the products being transported. Some companies or government agencies require that vehicles transporting flammable liquids or hazardous materials carry first aid kits, fire extinguishers, spill clean-up materials and portable hazard warning devices or signals to alert motorists if the vehicle is stopped alongside a highway.

Special equipment and techniques are required if a tank car or tank truck needs to be emptied of product as the result of an accident or rollover. Removal of product through fixed piping and valves or by using special knock-out plates on tank truck hatches is preferred; however, under certain conditions holes may be drilled in tanks using prescribed safe work procedures. Regardless of the method of removal, tanks should be grounded and a bond connection provided between the tank being emptied and the receiving tank.

Cleaning tank cars and tank trucks

Entering a tank car or tank truck compartment for inspection, cleaning, maintenance or repair is a hazardous activity requiring that all ventilation, testing, gas freeing and other confined-space entry and permit system requirements be followed in order to assure a safe operation. Cleaning tank cars and tank trucks is not any different from cleaning petroleum-product storage tanks, and all the same safety and health exposure precautions and procedures apply. Tank cars and tank trucks may contain residue of flammable, hazardous or toxic materials in sumps and unloading piping, or have been unloaded using an inert gas, such as nitrogen, so that what may appear to be a clean, safe space is not. Tanks which have contained crude oil, residues, asphalt or high-melting-point products may need to be steam or chemically cleaned prior to ventilation and entry, or may have a pyrophoric hazard. Ventilating tanks to free them from vapours and toxic or inert gases may be accomplished by opening the lowest and furthest valve or connection on each tank or compartment and placing an air eductor at the furthest top opening. Monitoring should be performed prior to entry without respiratory protection to assure that all of the corners and low spots in the tank, such as sumps, have been thoroughly vented, and ventilation should continue while working in the tank.

Aboveground Tank Storage of Liquid Petroleum Products

Crude oil, gas, LNG and LPG, processing additives, chemicals and petroleum products are stored in aboveground and underground atmospheric (non-pressure) and pressure storage tanks. Storage tanks are located at the ends of feeder lines and gathering lines, along truck pipelines, at marine loading and unloading facilities and in refineries, terminals and bulk plants. This section covers aboveground atmospheric storage tanks in refinery, terminal and bulk plant tank farms. (Information concerning aboveground pressure tanks is covered below, and information concerning underground tanks and small aboveground tanks is in the article “Motor vehicle fuelling and servicing operations”.)

Terminals and bulk plants

Terminals are storage facilities which generally receive crude oil and petroleum products by trunk pipeline or marine vessel. Terminals store and redistribute crude oil and petroleum products to refineries, other terminals, bulk plants, service stations and consumers by pipelines, marine vessels, railroad tank cars and tank trucks. Terminals may be owned and operated by oil companies, pipeline companies, independent terminal operators, large industrial or commercial consumers or petroleum product distributors.

Bulk plants are usually smaller than terminals and typically receive petroleum products by rail tank car or tank truck, normally from terminals but occasionally direct from refineries. Bulk plants store and redistribute products to service stations and consumers by tank truck or tank wagon (small tank trucks of approximately 9,500 to 1,900 l capacity). Bulk plants may be operated by oil companies, distributors or independent owners.

Tank farms

Tank farms are groupings of storage tanks at producing fields, refineries, marine, pipeline and distribution terminals and bulk plants which store crude oil and petroleum products. Within tank farms, individual tanks or groups of two or more tanks are usually surrounded by enclosures called berms, dykes or fire walls. These tank farm enclosures may vary in construction and height, from 45-cm earth berms around piping and pumps inside dykes to concrete walls that are taller than the tanks they surround. Dykes may be built of earth, clay or other materials; they are covered with gravel, limestone or sea shells to control erosion; they vary in height and are wide enough for vehicles to drive along the top. The primary functions of these enclosures are to contain, direct and divert rain water, physically separate tanks to prevent the spread of fire in one area to another, and to contain a spill, release, leak or overflow from a tank, pump or pipe within the area.

Dyke enclosures may be required by regulation or company policy to be sized and maintained to hold a specific amount of product. For example, a dyke enclosure may need to contain at least 110% of the capacity of the largest tank therein, allowing for the volume displaced by the other tanks and the amount of product remaining in the largest tank after hydrostatic equilibrium is reached. Dyke enclosures may also be required to be constructed with impervious clay or plastic liners to prevent spilled or released product from contaminating soil or groundwater.

Storage tanks

There are a number of different types of vertical and horizontal aboveground atmospheric and pressure storage tanks in tank farms, which contain crude oil, petroleum feedstocks, intermediate stocks or finished petroleum products. Their size, shape, design, configuration, and operation depend on the amount and type of products stored and company or regulatory requirements. Aboveground vertical tanks may be provided with double bottoms to prevent leakage onto the ground and cathodic protection to minimize corrosion. Horizontal tanks may be constructed with double walls or placed in vaults to contain any leakage.

Atmospheric cone roof tanks

Cone roof tanks are aboveground, horizontal or vertical, covered, cylindrical atmospheric vessels. Cone roof tanks have external stairways or ladders and platforms, and weak roof to shell seams, vents, scuppers or overflow outlets; they may have appurtenances such as gauging tubes, foam piping and chambers, overflow sensing and signalling systems, automatic gauging systems and so on.

When volatile crude oil and flammable liquid petroleum products are stored in cone roof tanks there is an opportunity for the vapour space to be within the flammable range. Although the space between the top of the product and the tank roof is normally vapour rich, an atmosphere in the flammable range can occur when product is first put into an empty tank or as air enters the tank through vents or pressure/vacuum valves when product is withdrawn and as the tank breathes during temperature changes. Cone roof tanks may be connected to vapour recovery systems.

Conservation tanks are a type of cone roof tank with an upper and lower section separated by a flexible membrane designed to contain any vapour produced when the product warms up and expands due to exposure to sunlight in the daytime and to return the vapour to the tank when it condenses as the tank cools down at night. Conservation tanks are typically used to store aviation gasoline and similar products.

Atmospheric floating roof tanks

Floating roof tanks are aboveground, vertical, open top or covered cylindrical atmospheric vessels that are equipped with floating roofs. The primary purpose of the floating roof is to minimize the vapour space between the top of the product and the bottom of the floating roof so that it is always vapour rich, thus precluding the chance of a vapour-air mixture in the flammable range. All floating roof tanks have external stairways or ladders and platforms, adjustable stairways or ladders for access to the floating roof from the platform, and may have appurtenances such as shunts which electrically bond the roof to the shell, gauging tubes, foam piping and chambers, overflow sensing and signalling systems, automatic gauging systems and so on. Seals or boots are provided around the perimeter of floating roofs to prevent product or vapour from escaping and collecting on the roof or in the space above the roof.

Floating roofs are provided with legs which may be set in high or low positions depending on the type of operation. Legs are normally maintained in the low position so that the greatest possible amount of product can be withdrawn from the tank without creating a vapour space between the top of the product and the bottom of the floating roof. As tanks are brought out of service prior to entry for inspection, maintenance, repair or cleaning, there is a need to adjust the roof legs into the high position to allow room to work under the roof once the tank is empty. When the tank is returned to service, the legs are readjusted into the low position after it is filled with product.

Aboveground floating roof storage tanks are further classified as external floating roof tanks, internal floating roof tanks or covered external floating roof tanks.

External (open top) floating roof tanks are those with floating covers installed on open-top storage tanks. External floating roofs are usually constructed of steel and provided with pontoons or other means of flotation. They are equipped with roof drains to remove water, boots or seals to prevent vapour releases and adjustable stairways to reach the roof from the top of the tank regardless of its position. They may also have secondary seals to minimize release of vapour to the atmosphere, weather shields to protect the seals and foam dams to contain foam in the seal area in case of a fire or seal leak. Entry onto external floating roofs for gauging, maintenance or other activities may be considered confined-space entry, depending on the level of the roof below the top of the tank, the products contained in the tank and government regulations and company policy.

Internal floating roof tanks usually are cone roof tanks which have been converted by installing buoyant decks, rafts or internal floating covers inside the tank. Internal floating roofs are typically constructed of various types of sheet metal, aluminium, plastic or metal-covered plastic expanded foam, and their construction may be of the pontoon or pan type, solid buoyant material, or a combination of these. Internal floating roofs are provided with perimeter seals to prevent vapour from escaping into the portion of the tank between the top of the floating roof and the exterior roof. Pressure/vacuum valves or vents are usually provided at the top of the tank to control any hydrocarbon vapours which may accumulate in the space above the internal floater. Internal floating roof tanks have ladders installed for access from the cone roof to the floating roof. Entry onto internal floating roofs for any purpose should be considered confined-space entry.

Covered (external) floating roof tanks are basically external floating roof tanks that have been retrofitted with a geodesic dome, snow cap or similar semi-fixed cover or roof so that the floating roof is no longer open to the atmosphere. Newly constructed covered external floating roof tanks may incorporate typical floating roofs designed for internal floating roof tanks. Entry onto covered external floating roofs for gauging, maintenance or other activities may be considered confined-space entry, depending on the construction of the dome or cover, the level of the roof below the top of the tank, the products contained in the tank and government regulations and company policy.

Pipeline and marine receipts

An important safety, product quality and environmental concern in tank storage facilities is to prevent intermixing of products and overfilling tanks by developing and implementing safe operating procedures and work practices. Safe operation of storage tanks depends on receiving product into tanks within their defined capacity by designating receiving tanks prior to delivery, gauging tanks to determine the available capacity and ensuring that valves are properly aligned and that only the receiving tank inlet is opened, so the correct amount of product is delivered into the assigned tank. Drains in dyke areas surrounding tanks receiving product should normally be kept closed during receipt in case an overfill or spill occurs. Overfill protection and prevention can be accomplished by a variety of safe operating practices, including manual controls and automatic detection, signalling and shut-down systems and a means of communication, all of which should be mutually understood and acceptable to product transfer personnel at the pipeline, marine vessel and terminal or refinery.

Government regulations or company policy may require that automatic product level detection devices and signal and shut-down systems be installed on tanks receiving flammable liquids and other products from trunk pipelines or marine vessels. Where such systems are installed, electronic system integrity tests should be conducted on a regular basis or prior to product transfer, and if the system fails, transfers should follow manual receipt procedures. Receipts should be monitored manually or automatically, onsite or from a remote control location, to ensure that operations are proceeding as planned. Upon completion of transfer, all valves should be returned to normal operating position or set for the next receipt. Pumps, valves, pipe connections, bleeder and sample lines, manifold areas, drains and sumps should be inspected and maintained to assure good condition and to prevent spills and leakage.

Tank gauging and sampling

Tank storage facilities should establish procedures and safe work practices for gauging and sampling crude oil and petroleum products which take into consideration the potential hazards involved with each product stored and each type of tank in the facility. Although tank gauging is often done using automatic mechanical or electronic devices, manual gauging should be performed at scheduled intervals to assure the accuracy of the automatic systems.

Manual gauging and sampling operations usually require the operator to climb to the top of the tank. When gauging floating roof tanks, the operator then has to descend onto the floating roof unless the tank is fitted with gauging and sampling tubes that are accessible from the platform. With cone roof tanks, the gauger must open a roof hatch in order to lower the gauge into the tank. Gaugers should be aware of the confined-space entry requirements and potential hazards when entering onto covered floating roofs or down upon open-top floating roofs which are below established height levels. This may require the use of monitoring devices, such as oxygen, combustible gas and hydrogen sulphide detectors and personal and respiratory protective equipment.

Product temperatures and samples may be taken at the same time as manual gauging is conducted. Temperatures may also be recorded automatically and samples obtained from built-in sample connections. Manual gauging and sampling should be restricted while tanks are receiving product. Following the completion of receipt, a relaxation period of from 30 minutes to 4 hours, depending on the product and company policy, should be required to allow any electrostatic build-up to dissipate before conducting manual sampling or gauging. Some companies require that communications or visual contact be established and maintained between gaugers and other facility personnel when descending upon floating roofs. Entry onto tank roofs or platforms for gauging, sampling or other activities should be restricted during thunderstorms.

Tank venting and cleaning

Storage tanks are taken out of service for inspection, testing, maintenance, repair, retrofitting and tank cleaning as needed or at regular intervals dependent on government regulations, company policy and operating service requirements. Although tank venting, cleaning and entry is a potentially hazardous operation, this work can be accomplished without incident, provided that proper procedures are established and safe work practices followed. Without such precautions, injury or damage can occur from explosions, fires, lack of oxygen, toxic exposures and physical hazards.

Preliminary preparations

A number of preliminary preparations are required after it has been decided that a tank needs to be taken out of service for inspection, maintenance or cleaning. These include: scheduling storage and supply alternatives; reviewing the tank history to determine whether it has ever contained leaded product or has previously been cleaned and certified lead free; determining the amount and type of products contained and how much residue will remain in the tank; inspecting the outside of the tank, the surrounding area and the equipment to be used for product removal, vapour freeing and cleaning; assuring that personnel are trained, qualified and familiar with facility permit and safety procedures; assigning job responsibilities in accordance with the facility’s confined-space entry and hot- and safe-work permit requirements; and holding a meeting between terminal and tank cleaning personnel or contractors before tank cleaning or construction starts.

Control of ignition sources

After the removal of all available product from the tank through fixed piping, and before any water draws or sample lines are opened, all sources of ignition should be removed from the surrounding area until the tank is declared vapour free. Vacuum trucks, compressors, pumps and other equipment which is electrically or motor driven should be located upwind, either on top of or outside the dyke area, or, if inside the dyke area, at least 20 m from the tank or any other sources of flammable vapours. Tank preparation, venting and cleaning activities should cease during electrical storms.

Removing residue

The next step is to remove as much remaining product or residue in the tank as possible through pipeline and waterdraw connections. A safe-work permit may be issued for this work. Water or distillate fuel may be injected into the tank through fixed connections to help float product out of the tank. Residue removed from tanks that have contained sour crude should be kept wet until disposal to avoid spontaneous combustion.

Isolating the tank

After all available product has been removed through fixed piping, all piping connected to the tank, including product lines, vapour recovery lines, foam piping, sample lines and so on, should be disconnected by closing the valves nearest the tank and inserting blinds in the lines on the tank side of the valve to prevent any vapours from entering the tank from the lines. The portion of piping between the blinds and the tank should be drained and flushed. Valves outside the dyke area should be closed and locked or tagged. Tank pumps, internal mixers, cathodic protection systems, electronic gauging and level detection systems and so on should be disconnected, de-energized and locked or tagged out.

Vapour freeing

The tank is now ready to be made vapour free. Intermittent or continuous vapour testing should be conducted and work in the area restricted during tank ventilation. Natural ventilation, through opening the tank to the atmosphere, is not usually preferred, since it is neither as fast nor as safe as forced ventilation. There are a number of methods of mechanically venting a tank, depending on its size, construction, condition and internal configuration. In one method, cone roof tanks may be vapour freed by placing an eductor (a portable ventilator) at a hatch on the top of the tank, starting it slowly while a hatch at the bottom of the tank is opened and then setting it on high speed to draw air and vapours through the tank.

A safe- or hot-work permit should be issued covering ventilation activities. All blowers and eductors should be securely bonded to the tank shell to prevent electrostatic ignition. For safety purposes, blowers and eductors should preferably be operated by compressed air; however, explosion-proof electric- or steam-driven motors have been used. Internal floating roof tanks may need to have the portions above and below the floating roof vented separately. If vapours are discharged from a bottom hatch, a vertical tube at least 4 m above ground level and no lower than the surrounding dyke wall is needed in order to prevent vapours from collecting at low levels or reaching a source of ignition before dissipating. If necessary, vapours may be directed to the facility vapour recovery system.

As ventilation progresses, the remaining residue can be washed down and removed through the open bottom hatch by water and suction hoses, both of which should be bonded to the tank shell to prevent electrostatic ignition. Tanks which have contained sour crude oil or high-sulphur residual products may generate spontaneous heat and ignite as they dry out during ventilation. This should be avoided by wetting the inside of the tank with water to blanket the deposits from air and prevent a rise in temperature. Any iron sulphide residue should be removed from the open hatch to prevent ignition of vapours during ventilation. Workers engaged in washdown, removal and wetting activities should wear appropriate personal and respiratory protection.

Initial entry, inspection and certification

An indication of the progress being made in vapour freeing the tank can be obtained by monitoring vapours at the point of eduction during ventilation. Once it appears that the flammable vapour level is below that established by regulatory agencies or company policy, entry can be made into the tank for inspection and testing purposes. The entrant should wear appropriate personal and air-supplied respiratory protection; after testing the atmosphere at the hatch and obtaining an entry permit, the worker may enter the tank to continue testing and inspection. Checks for obstructions, falling roofs, weak supports, holes in the floor and other physical hazards should be conducted during the inspection.

Cleaning, maintenance and repair

As ventilation continues and the vapour levels in the tank drop lower, permits may be issued allowing entry by workers with appropriate personal and respiratory equipment, if needed, to start cleaning the tank. Monitoring for oxygen, flammable vapours and toxic atmospheres should continue, and if the levels inside the tank exceed those established for entry, the permit should automatically expire and the entrants should immediately leave the tank until the safe level is again achieved and the permit is reissued. Ventilation should continue during cleaning operations as long as any residue or sludge remains in the tank. Only low-voltage lighting or approved flashlights should be used during inspection and clean-up.

After tanks have been cleaned and dried, a final inspection and testing should be conducted before maintenance, repair or retrofitting work is started. Careful inspection of sumps, wells, floor plates, floating roof pontoons, supports and columns is needed to assure that no leaks have developed which allowed product to enter these spaces or seep beneath the floor. Spaces between foam seals and weather shields or secondary containment should also be inspected and tested for vapours. If the tank has previously contained leaded gasoline, or if no tank history is available, a lead-in-air test should be conducted and the tank certified lead free before workers are allowed inside without air-supplied respiratory equipment.

A hot-work permit should be issued covering welding, cutting and other hot work, and a safe-work permit issued to cover other repair and maintenance activities. Welding or hot work can create toxic or noxious fumes inside the tank, requiring monitoring, respiratory protection and continued ventilation. When tanks are to be retrofitted with double bottoms or internal floating roofs, a large hole is often cut into the side of the tank to provide unrestricted access and avoid the need for confined-space entry permits.

Blast cleaning and painting the outside of tanks usually follows tank cleaning and is completed before the tank is returned to service. These activities, together with cleaning and painting tank farm piping, may be performed while tanks and pipes are in service, by implementing and following prescribed safety procedures, such as conducting monitoring for hydrocarbon vapours and stopping blast cleaning while nearby tanks are receiving flammable liquid products. Blast cleaning with sand has the potential for hazardous exposure to silica; therefore, many government agencies and companies require the use of special non-toxic blast cleaning materials or grit, which may be collected, cleaned and recycled. Special vacuum collection blast cleaning devices may be used in order to avoid contamination when cleaning leaded paint from tanks and piping. Following blast cleaning, spots in the tank walls or piping suspected of having leaks and seeps should be tested and repaired before being painted.

Returning the tank to service

In preparation for return to service upon completion of tank cleaning, inspection, maintenance or repair, the hatches are closed, all blinds are removed and the piping is reconnected to the tank. Valves are unlocked, opened and aligned, and mechanical and electrical devices are reactivated. Many government agencies and companies require tanks to be hydrostatically tested to assure that there are no leaks before they are returned to service. Since a considerable amount of water is required to obtain the necessary pressure head for an accurate test, a water bottom topped with diesel fuel is often used. Upon completion of the testing, the tank is emptied and made ready to receive product. After receipt is completed and a relaxation time has elapsed, the legs on floating roof tanks are reset into the low position.

Fire protection and prevention

Whenever hydrocarbons are present in closed containers such as storage tanks in refineries, terminals and bulk plants, the potential exists for release of liquids and vapours. These vapours could mix with air in the flammable range and, if subjected to a source of ignition, cause an explosion or fire. Regardless of the capability of fire protection systems and personnel in the facility, the key to fire protection is fire prevention. Spills and releases should be stopped from entering sewers and drainage systems. Small spills should be covered with wet blankets, and larger spills with foam, to prevent vapours from escaping and mixing with air. Sources of ignition in areas when hydrocarbon vapours may be present should be eliminated or controlled. Portable fire extinguishers should be carried on service vehicles and located at accessible and strategic positions throughout the facility.

The establishment and implementation of safe work procedures and practices such as hot- and safe- (cold-) work permit systems, electrical classification programmes, lockout/tagout programmes, and employee and contractor training and education is critical to preventing fires. Facilities should develop preplanned emergency procedures, and employees should be knowledgeable in their responsibilities for reporting and responding to fires and evacuation. Telephone numbers of responsible persons and agencies to be notified in case of an emergency should be posted at the facility and a means of communication provided. Local fire departments, emergency response, public safety and mutual aid organizations should also be aware of the procedures and familiar with the facility and its hazards.

Hydrocarbon fires are controlled by one or a combination of methods, as follows:

  • Removing fuel. One of the best and easiest methods of controlling and extinguishing a hydrocarbon fire is to shut off the source of fuel by closing a valve, diverting product flow or, if a small amount of product is involved, controlling exposures while allowing the product to burn away. Foam may also be used to cover hydrocarbon spills to prevent vapours from being emitted and mixing with the air.
  • Removing oxygen. Another method is to shut off the supply of air or oxygen by smothering fires with foam or water fog, or by using carbon dioxide or nitrogen to displace air in enclosed spaces.
  • Cooling. Water fog, mist or spray and carbon dioxide may be used to extinguish certain petroleum product fires by cooling the temperature of the fire below the product’s ignition temperature and by stopping vapours from forming and mixing with air.
  • Interrupting combustion. Chemicals such as dry powders and halon extinguish fires by interrupting the chemical reaction of the fire.

 

Storage tank fire protection

Storage tank fire protection and prevention is a specialized science which depends on the interrelationship of tank type, condition and size; product and amount stored in the tank; tank spacing, dyking and drainage; facility fire protection and response capabilities; outside assistance; and company philosophy, industry standards and government regulations. Storage tank fires may be easy or very difficult to control and extinguish, depending primarily on whether the fire is detected and attacked during its initial inception. Storage tank operators should refer to the numerous recommended practices and standards developed by organizations such as the American Petroleum Institute (API) and the US National Fire Protection Association (NFPA), which cover storage tank fire prevention and protection in great detail.

If open-top floating roof storage tanks are out of round or if the seals are worn or not tight against the tank shells, vapours can escape and mix with air, forming flammable mixtures. In such situations, when lightning strikes, fires may occur at the point where the roof seals meet the shell of the tank. If detected early, small seal fires can often be extinguished by a hand-carried dry powder extinguisher or with foam applied from a foam hose or foam system.

If a seal fire cannot be controlled with hand extinguishers or hose streams, or if a large fire is in progress, foam may be applied onto the roof through fixed or semi-fixed systems or by large foam monitors. Precautions are necessary when applying foam onto the roofs of floating roof tanks; if too much weight is placed on the roof, it may tilt or sink, allowing a large surface area of product to be exposed and become involved in the fire. Foam dams are used on floating roof tanks to trap foam in the area between the seals and the tank shell. As the foam settles, water drains out under the foam dams and should be removed through the tank roof drain system to avoid overweighing and sinking the roof.

Depending on government regulations and company policy, storage tanks may be provided with fixed or semi-fixed foam systems which include: piping to the tanks, foam risers and foam chambers on the tanks; subsurface injection piping and nozzles inside the bottom of tanks; and distribution piping and foam dams on the tops of tanks.With fixed systems, foam-water solutions are generated in centrally located foam houses and pumped to the tank through a piping system. Semi-fixed foam systems typically use portable foam tanks, foam generators and pumps which are brought to the tank involved, connected to a water supply and connected to the tank’s foam piping.

Water-foam solutions may also be centrally generated and distributed within the facility through a system of piping and hydrants, and hoses would be used to connect the nearest hydrant to the tank’s semi-fixed foam system. Where tanks are not provided with fixed or semi-fixed foam systems, foam may be applied onto the tops of tanks, using foam monitors, fire hoses and nozzles. Regardless of the method of application, in order to control a fully involved tank fire, a specific amount of foam must be applied using special techniques at a specific concentration and rate of flow for a minimum amount of time depending primarily on the size of the tank, the product involved and the surface area of the fire. If there is not enough foam concentrate available to meet the required application criteria, the possibility of control or extinguishment is minimal.

Only trained and knowledgeable fire-fighters should be allowed to use water to fight liquid petroleum tank fires. Instantaneous eruptions, or boil-overs, can occur when water turns into steam upon direct application onto tank fires involving crude or heavy petroleum products. As water is heavier than most hydrocarbon fuels, it will sink to the bottom of a tank and, if enough is applied, fill the tank and push the burning product up and over the top of the tank.

Water is typically used to control or extinguish spill fires around the outside of tanks so that valves can be operated to control product flow, to cool the sides of involved tanks to prevent boiling liquid–expanding vapour explosions (BLEVEs—see the section “Fire hazards of LHGs” below) and to reduce the effect of heat and flame impingement on adjacent tanks and equipment. Because of the need for specialized training, materials and equipment, rather than allow employees to attempt to extinguish tank fires, many terminals and bulk plants have established a policy to remove as much product as possible from the involved tank, protect adjacent structures from heat and flame and allow the remaining product in the tank to burn under controlled conditions until the fire burns out.

Terminal and bulk plant health and safety

Storage tank foundations, supports and piping should be regularly inspected for corrosion, erosion, settling or other visible damage to prevent loss or degradation of product. Tank pressure/vacuum valves, seals and shields, vents, foam chambers, roof drains, water draw-off valves and overfill detection devices should be inspected, tested and maintained on a regular schedule, including removal of ice in the winter. Where flame arrestors are installed on tank vents or in vapour recovery lines, they have to be inspected and cleaned regularly and kept free of frost in the winter to ensure proper operation. Valves on tank outlets which close automatically in case of fire or drop in pressure should be checked for operability.

Dyke surfaces should drain or slope away from tanks, pumps and piping to remove any spilled or released product to a safe area. Dyke walls should be maintained in good condition, with drain valves kept closed except when draining water and dyke areas excavated as needed to maintain design capacity. Stairways, ramps, ladders, platforms and railings to loading racks, dykes and tanks should be maintained in a safe condition, free of ice, snow and oil. Leaking tanks and piping should be repaired as soon as possible. The use of victaulic or similar couplings on piping within dyked areas which could be exposed to heat should be discouraged to prevent lines from opening during fires.

Safety procedures and safe work practices should be established and implemented, and training or education provided, so that terminal and bulk plant operators, maintenance personnel, tank truck drivers and contractor personnel can work safely. These should include, as a minimum, information concerning the basics of hydrocarbon fire ignition, control and extinguishment; hazards and protection from exposures to toxic substances such as hydrogen sulphide and polynuclear aromatics in crude oil and residual fuels, benzene in gasoline and additives such as tetraethyl lead and methyl-tert-butyl ether (MTBE); emergency response actions; and normal physical and climatic hazards associated with this activity.

Asbestos or other insulation may be present in the facility as protection for tanks and piping. Appropriate safe-work and personal protective measures should be established and followed for handling, removing and disposing of such materials.

Environmental protection

Terminal operators and employees should be aware of and comply with government regulations and company policies covering environmental protection of ground and surface water, soil and air from pollution by petroleum liquids and vapours, and for handling and removing hazardous waste.

  • Water contamination. Many terminals have oil/water separators to handle contaminated water from tank containment areas, run-off from loading racks and parking areas and water drained from tanks and open-top tank roofs. Terminals may be required to meet established water quality standards and obtain permits before discharging water.
  • Air pollution. Air pollution prevention includes minimizing releases of vapours from valves and vents. Vapour recovery units collect vapours from loading racks and marine docks, even when tanks are vented prior to entry. These vapours are either processed and returned to storage as liquids or burned.
  • Spills on land and water. Government agencies and companies may require that oil storage facilities have spill prevention control and counter-measure plans, and that personnel be trained and aware of the potential hazards, notifications to be made and the actions to take in case of a spill or release. In addition to handling spills within the terminal facility, personnel are often trained and equipped to respond to offsite emergencies, such as a tank truck rollover.
  • Sewage and hazardous waste. Terminals may be required to meet regulatory requirements and obtain permits for discharge of sewage and oily waste to public or privately owned treatment works. Various government requirements and company procedures may apply to the onsite storage and handling of hazardous waste such as asbestos insulation, tank cleaning residue and contaminated product. Workers should be trained in this activity and be made aware of the potential hazards from exposures which could occur.

 

LHG Storage and Handling

Bulk storage tanks

LHGs are stored in large bulk storage tanks at the point of process (gas and oil fields, gas plants and refineries) and at the point of distribution to the consumer (terminals and bulk plants). The two most commonly used methods of bulk storage of LHGs are:

  • Under high pressure at ambient temperature. LHG is stored in steel pressure tanks (at 1.6 to 1.8 mPa) or in underground impermeable rock or salt formations.
  • Under pressure close to atmospheric at low temperature. LHG is stored in thin-walled, heat-insulated steel storage tanks; in reinforced concrete tanks above and below ground; and in underground cryogenic storage tanks. Pressure is maintained close to atmospheric (0.005 to 0.007 mPa) at a temperature of –160°C for LNG stored in cryogenic underground storage tanks.

 

LPG bulk storage vessels are either cylindrically (bullet) shaped horizontal tanks (40 to 200 m3) or spheres (up to 8,000 m3). Refrigerated storage is typical for storage in excess of 2,400 m3. Both horizontal tanks, which are fabricated in shops and transported to the storage site, and spheres, which are built onsite, are designed and constructed in accordance with rigid specifications, codes and standards.

The design pressure of storage tanks should not be less than the vapour pressure of the LHG to be stored at the maximum service temperature. Tanks for propane-butane mixtures should be designed for 100% propane pressure. Consideration should be given to additional pressure requirements resulting from the hydrostatic head of the product at maximum fill and the partial pressure of non-condensible gases in the vapour space. Ideally, liquefied hydrocarbon gas storage vessels should be designed for full vacuum. If not, vacuum relief valves must be provided. Design features should also include pressure relief devices, liquid level gauges, pressure and temperature gauges, internal shut-off valves, back flow preventers and excess flow check valves. Emergency fail-safe shut-down valves and high level signals may also be provided.

Horizontal tanks are either installed aboveground, placed on mounds or buried underground, typically downwind from any existing or potential sources of ignition. If the end of a horizontal tank ruptures from over-pressurization, the shell will be propelled in the direction of the other end. Therefore, it is prudent to place an aboveground tank so that its length is parallel to any important structure (and so that neither end points toward any important structure or equipment). Other factors include tank spacing, location, and fire prevention and protection. Codes and regulations specify minimum horizontal distances between pressurized liquefied hydrocarbon gas storage vessels and adjoining properties, tanks and important structures as well as potential sources of ignition, including processes, flares, heaters, power transmission lines and transformers, loading and unloading facilities, internal combustion engines and gas turbines.

Drainage and spill containment are important considerations in designing and maintaining liquid hydrocarbon gas tank storage areas in order to direct spills to a location where they will minimize risk to the facility and surrounding areas. Dyking and impounding may be used where spills present a potential hazard to other facilities or to the public. Storage tanks are not usually dyked, but the ground is graded so that vapours and liquids do not collect underneath or around the storage tanks, in order to keep burning spills from impinging upon storage tanks.

Cylinders

LHGs for use by consumers, either LNG or LPG, are stored in cylinders at temperatures above their boiling points at normal temperature and pressure. All LNG and LPG cylinders are provided with protective collars, safety valves and valve caps. The basic types of consumer cylinders in use are:

  • vapour withdrawal (1/2 to 50 kg) cylinders used by consumers, with larger ones usually refillable on an exchange basis with the supplier
  • liquid withdrawal cylinders for dispensing into small consumer-owned refillable cylinders
  • motor vehicle fuel cylinders, including vehicle cylinders (40 kg) permanently installed as fuel tanks on motor vehicles and filled and used in the horizontal position, and industrial truck cylinders designed to be stored, filled and handled in the upright position, but used in the horizontal position.

 

Properties of hydrocarbon gases

According to the NFPA, flammable (combustible) gases are those which burn in the normal concentrations of oxygen in air. The burning of flammable gases is similar to flammable hydrocarbon liquid vapours, as a specific ignition temperature is needed to initiate the burning reaction, and each will burn only within a certain defined range of gas-air mixtures. Flammable liquids have a flashpoint, which is the temperature (always below the boiling point) at which they emit sufficient vapours for combustion. There is no apparent flashpoint for flammable gases, since they are normally at temperatures above their boiling points, even when liquefied, and are therefore always at temperatures well in excess of their flashpoints.

The NFPA (1976) defines compressed and liquefied gases as follows:

  • “Compressed gases are those which at all normal atmospheric temperatures inside their containers, exist solely in the gaseous state under pressure.”
  • “Liquefied gases are those which at normal atmospheric temperatures inside their containers, exist partly in the liquid state and partly in the gaseous state, and are under pressure as long as any liquid remains in the container.”

 

The major factor which determines the pressure inside the vessel is the temperature of the liquid stored. When exposed to the atmosphere, the liquefied gas very rapidly vaporizes, travelling along the ground or water surface unless dispersed into the air by wind or mechanical air movement. At normal atmospheric temperatures, about one-third of the liquid in the container will vaporize.

Flammable gases are further classified as fuel gas and industrial gas. Fuel gases, including natural gas (methane) and LPGs (propane and butane), are burned with air to produce heat in ovens, furnaces, water heaters and boilers. Flammable industrial gases, such as acetylene, are used in processing, welding, cutting and heat-treating operations. The differences in combustion properties of LNG and LPGs are shown in table 1.

Table 1. Typical approximate combustion properties of liquified hydrocarbon gases.

Type gas

Flammable range
(% gas in air)

Vapour pressure
(psig at 21 ºC)

Normal init. boiling
point (ºC)

Weight (pounds/gal)

BTU per ft3

Specific gravity
(Air = 1)

LNG

4.5–14

1.47

–162

3.5–4

1,050

9.2–10

LPG (propane)

2.1–9.6

132

–46

4.24

2,500

1.52

LPG (butane)

1.9–8.5

17

–9

4.81

3,200

2.0

 

Safety hazards of LPG and LNG

The safety hazards applicable to all LHGs are associated with flammability, chemical reactivity, temperature and pressure. The most serious hazard with LHGs is the unplanned release from containers (canisters or tanks) and contact with an ignition source. Release can occur by failure of the container or valves for a variety of reasons, such as overfilling a container or from overpressure venting when the gas expands due to heating.

The liquid phase of LPG has a high coefficient of expansion, with liquid propane expanding 16 times and liquid butane 11 times as much as water with the same rise in temperature. This property must be considered when filling containers, as free space must be left for the vapour phase. The correct quantity to be filled is determined by a number of variables, including the nature of the liquefied gas, temperature at time of filling and expected ambient temperatures, size, type (insulated or uninsulated) and location of container (above or below ground). Codes and regulations establish allowable quantities, known as “filling densities”, which are specific for individual gases or families of similar gases. Filling densities may be expressed by weight, which are absolute values, or by liquid volume, which must always be temperature corrected.

The maximum amount that LPG pressure containers should be filled with liquid is 85% at 40 ºC (less at higher temperatures). Because LNG is stored under low temperatures, LNG containers may be liquid filled from 90% to 95%. All containers are provided with overpressure relief devices which normally discharge at pressures relating to liquid temperatures above normal atmospheric temperatures. As these valves cannot reduce the internal pressure to atmospheric, the liquid will always be at a temperature above its normal boiling point. Pure compressed and liquefied hydrocarbon gases are non-corrosive to steel and most copper alloys. However, corrosion can be a serious problem when sulphur compounds and impurities are present in the gas.

LPGs are 1-1/2 to 2 times heavier than air and, when released in air, tend to quickly disperse along the ground or water surface and collect in low areas. However, as soon as the vapour is diluted by air and forms a flammable mixture, its density is essentially the same as air, and it disperses differently. Wind will significantly reduce the dispersion distance for any size of leak. LNG vapours react differently from LPG. Because natural gas has a low vapour density (0.6), it will mix and disperse rapidly in open air, reducing the chance of forming a flammable mixture with air. Natural gas will collect in enclosed spaces and form vapour clouds which could be ignited. Figure 4 indicates how a liquefied natural gas vapour cloud spreads downwind in different spill situations.

Figure 4. Extension of LNG vapour cloud downwind from different spills (wind speed 8.05 km/h).

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Although LHG is colourless, when released in air its vapours will be noticeable due to the condensation and freezing of water vapour contained in the atmosphere which is contacted by the vapour. This may not occur if the vapour is near ambient temperature and its pressure is relatively low. Instruments are available which can detect the presence of leaking LHG and signal an alarm at levels as low as 15 to 20% of the lower flammable limit (LFL). These devices may also stop all operations and activate suppression systems, should the concentrations of gas reach 40 to 50% of the LFL. Some industrial operations provide forced ventilation to keep leaking fuel-air concentrations below the lower flammable limit. Heater and furnace burners may also have devices which automatically stop the flow of gas if the flame is extinguished.

LHG leakage from tanks and containers may be minimized by the use of limiting and flow control devices. When decompressed and released, LHG will flow out of containers with a low negative pressure and low temperature. The auto refrigeration temperature of the product at the lower pressure must be considered when selecting materials of construction for containers and valves, to prevent metal embrittlement followed by rupture or failure due to exposure to low temperatures.

LHG can contain water in both its liquid and gaseous phases. Water vapour can saturate gas in a specific amount at a given temperature and pressure. If the temperature or pressure changes, or the water vapour content exceeds the evaporation limits, the water condenses. This can create ice plugs in valves and regulators and form hydrocarbon hydrate crystals in pipelines, devices and other apparatus. These hydrates can be decomposed by heating the gas, lowering the gas pressure or introducing materials, such as methanol, which reduce the water vapour pressure.

There are differences in the characteristics of compressed and liquefied gases which must be considered from safety, health and fire aspects. As an example, the differences in the characteristics of compressed natural gas and LNG are illustrated in table 2.

Table 2. Comparison of characteristics of compressed and liquified gas.

Type gas

Flammable range
(% gas in air)

Heat release rate (BTU/gal)

Storage condition

Fire risks

Health risks

Compressed natural gas

5.0–15

19,760

Gas at 2,400 to 4,000 psi

Flammable gas

Asphyxiant; overpressure

LNG

4.5–14

82,450

Liquid at 40–140 psi

Flammable gas 625:1 expansion ratio; BLEVE

Asphyxiant; cryogenic liquid

 

Health hazards of LHGs

The primary occupational injury concern in handling LHGs is the potential hazard of frostbite to the skin and eyes from contact with liquid during handling and storage activities including sampling, measuring, filling, receiving and delivery. As with other fuel gases, when improperly burned, compressed and liquefied hydrocarbon gases will emit undesirable levels of carbon monoxide.

Under atmospheric pressures and low concentrations, compressed and liquefied hydrocarbon gases are normally non-toxic, but they are asphyxiants—they will displace oxygen (air) if released in enclosed or confined spaces. Compressed and liquefied hydrocarbon gases may be toxic if they contain sulphur compounds, especially hydrogen sulphide. Because LHGs are colourless and odourless, safeguards include adding odourants, such as mercaptans, to consumer fuel gases to aid in leak detection. Safe work practices should be implemented to protect workers from exposure to mercaptans and other additives during storage and injection. Exposure to LPG vapours in concentrations at or above the LFL may cause a general central nervous system depression similar to anaesthesia gases or intoxicants.

Fire hazards of LHGs

Failure of liquefied gas (LNG and LPG) containers constitutes a more severe hazard than failure of compressed gas containers, as they release greater quantities of gas. When heated, liquefied gases react differently from compressed gases, because they are two-phase (liquid-vapour) products. As the temperature rises, the vapour pressure of the liquid is increased, resulting in increased pressure inside the container. The vapour phase first expands, followed by expansion of the liquid, which then compresses the vapour. The design pressure for LHG vessels is therefore assumed to be near that of the gas pressure at maximum possible ambient temperature.

When a liquefied gas container is exposed to fire, a serious condition can occur if the metal in the vapour space is allowed to heat. Unlike the liquid phase, the vapour phase absorbs little heat. This allows the metal to heat rapidly until a critical point is reached at which an instantaneous, catastrophic explosive failure of the container occurs. This phenomenon is known as a BLEVE. The magnitude of a BLEVE depends on the amount of liquid vaporizing when the container fails, the size of the pieces of exploded container, the distance they travel and the areas they impact. Uninsulated LPG containers may be protected against a BLEVE by applying cooling water to those areas of the container which are in the vapour phase (not in contact with LPG).

Other more common fire hazards associated with compressed and liquefied hydrocarbon gases include electrostatic discharge, combustion explosions, large open-air explosions and small leaks from pump seals, containers, valves, pipes, hoses and connections.

  • Electrostatic charges may be generated when LHG is shipped in pipelines, when loaded and unloaded, in blending and filtering and during tank cleaning.
  • Combustion explosions result when escaping gas or vapour is contained in a confined space or structure and combines with air to create a flammable mixture. When this flammable mixture contacts a source of ignition, it burns instantaneously and rapidly, producing extreme heat. The very hot air expands quickly, causing a considerable rise in pressure. If the space or structure is not strong enough to contain this pressure, a combustion explosion occurs.
  • Flammable gas fires result when there is no confinement of the escaping gas or vapours, or ignition occurs when only a small amount of gas has been released.
  • Large open-air explosions occur when a massive failure of a container releases a large vapour cloud of gas which is ignited before it disperses.

 

Controlling sources of ignition in hazardous areas is essential for the safe handling of compressed and liquefied hydrocarbon gases. This may be accomplished by establishing a permit system to authorize and control hot work, smoking, operation of motor vehicles or other internal combustion engines, and the use of open flames in areas where compressed and liquefied hydrocarbon gas is transported, stored and handled. Other safeguards include the use of properly classified electrical equipment and bonding and grounding systems to neutralize and dissipate static electricity.

The best means of reducing the fire hazard of leaking compressed or liquefied hydrocarbon gas is to stop the release, or shut off the flow of product, if possible. Although most LHGs will vaporize upon contact with air, lower vapour pressure LPGs, such as butane, and even some higher vapour pressure LPGs, such as propane, will pool if ambient temperatures are low. Water should not be applied to these pools, as it will create turbulence and increase the rate of vaporization. Vaporization from pool spills can be controlled by the careful application of foam. Water, if correctly applied against a leaking valve or small rupture, can freeze upon contact with the cold LHG and block the leak. LHG fires require controlling heat impingement upon storage tanks and containers by the application of cooling water. While compressed and liquefied hydrocarbon gas fires can be extinguished by the use of water spray and dry powder extinguishers, it is often more prudent to allow controlled burning so that a combustible explosive vapour cloud does not form and re-ignite should the gas continue to escape after the fire is extinguished.

 

Back

The very definition of the maritime setting is work and life that takes place in or around a watery world (e.g., ships and barges, docks and terminals). Work and life activities must first accommodate the macro-environmental conditions of the oceans, lakes or waterways in which they take place. Vessels serve as both workplace and home, so most habitat and work exposures are coexistent and inseparable.

The maritime industry comprises a number of sub-industries, including freight transportation, passenger and ferry service, commercial fishing, tankships and barge shipping. Individual maritime sub-industries consist of a set of merchant or commercial activities that are characterized by the type of vessel, targeted goods and services, typical practices and area of operations, and community of owners, operators and workers. In turn, these activities and the context in which they take place define the occupational and environmental hazards and exposures experienced by maritime workers.

Organized merchant maritime activities date back to the earliest days of civilized history. The ancient Greek, Egyptian and Japanese societies are examples of great civilizations where the development of power and influence was closely associated with having an extensive maritime presence. The importance of maritime industries to development of national power and prosperity has continued into the modern era.

The dominant maritime industry is water transportation, which remains the primary mode of international trade. The economies of most countries with ocean borders are heavily influenced by the receipt and export of goods and services by water. However, national and regional economies heavily dependent on the transport of goods by water are not limited to those which border oceans. Many countries removed from the sea have extensive networks of inland waterways.

Modern merchant vessels may process materials or produce goods as well as transport them. Globalized economies, restrictive land use, favourable tax laws and technology are among the factors which have spurred the growth of vessels that serve as both factory and means of transportation. Catcher-processor fishing vessels are a good example of this trend. These factory ships are capable of catching, processing, packaging and delivering finished sea food products to regional markets, as discussed in the chapter Fishing industry.

Merchant Transport Vessels

Similar to other transport vehicles, the structure, form and function of vessels closely parallel the vessel’s purpose and major environmental circumstances. For example, craft that transport liquids short distances on inland waterways will differ substantially in form and crew from those that carry dry bulk on trans-oceanic voyages. Vessels can be free moving, semi-mobile or permanently fixed structures (e.g., offshore oil-drilling rigs) and be self-propelled or towed. At any given time, existing fleets are comprised of a spectrum of vessels with a wide range of original construction dates, materials and degrees of sophistication.

Crew size will depend on the typical duration of trip, vessel purpose and technology, expected environmental conditions and sophistication of shore facilities. Larger crew size entails more extensive needs and elaborate planning for berthing, dining, sanitation, health care and personnel support. The international trend is toward vessels of increasing size and complexity, smaller crews and expanding reliance on automation, mechanization and containerization. Table 1 provides a categorization and descriptive summary of merchant vessel types.

Table 1. Merchant vessel types.

Vessel types

Description

Crew size

Freight ships

 

Bulk carrier

 

 

 

Break bulk

 

 

 

Container

 

 

 

Ore, bulk, oil  (OBO)

 

 

Vehicle

 

 

Roll-on roll- off (RORO)

Large vessel (200-600 feet (61-183 m)) typified by large open cargo holds and many voids; carry bulk cargoes such as grain and ore; cargo is loaded by chute, conveyor or shovel

 

Large vessel (200-600 feet (61-183 m)); cargo carried in bales, pallets, bags or boxes; expansive holds with between decks; may have tunnels

 

 

Large vessel (200-600 (61-183 m)) with open holds; may or may not have booms or cranes to handle cargo; containers are 20-40 feet (6.1-12.2 m) and stackable

 

 

Large vessel (200-600 feet (61-183 m)); holds are expansive and shaped to hold bulk ore or oil; holds are water tight, may have pumps and piping; many voids

 

 

Large vessel (200-600 feet (61-183 m)) with big sail area; many levels; vehicles can be self loading or boomed aboard

 

 

Large vessel (200-600 feet (61-183 m)) with big sail area; many levels; can carry other cargo in addition to vehicles

25-50

 

 

25-60

 

 

 

25-45

 

 

 

25-55

 

 

25-40

 

 

 

25-40

Tank ships

Oil

 

 

 

Chemical

 

 

 

Pressurized

Large vessel (200-1000 feet (61-305 m)) typified by stern house piping on deck; may have hose handling booms and large ullages with many tanks; can carry crude or processed oil, solvents and other petroleum products

 

Large vessel (200-1000 feet (61-305 m)) similar to oil tankship, but may have additional piping and pumps to handle multiple cargoes simultaneously; cargoes can be liquid, gas, powders or compressed solids

 

Usually smaller (200-700 feet (61-213.4 m)) than typical tankship, having fewer tanks, and tanks which are pressurized or cooled; can be chemical or petroleum products such as liquid natural gas; tanks are usually covered and insulated; many voids, pipes and pumps

25-50

 

 

25-50

 

 

15-30

 

Tug boats

Small to mid-size vessel (80-200 feet (24.4-61 m));  harbour, push boats, ocean going

3-15

Barge

Mid-size vessel (100-350 feet (30.5-106.7 m)); can be tank, deck, freight or vehicle; usually not manned or self-propelled; many voids

 

Drillships and rigs

Large, similar profile to bulk carrier; typified by large derrick; many voids, machinery, hazardous cargo and large crew; some are towed, others self propelled

40-120

Passenger

All sizes (50-700 feet (15.2-213.4 m)); typified by large number of crew and passengers (up to 1000+)

20-200

 

Morbidity and Mortality in the Maritime Industries

Health care providers and epidemiologists are often challenged to distinguish adverse health states due to work-related exposures from those due to exposures outside the workplace. This difficulty is compounded in the maritime industries because vessels serve as both workplace and home, and both exist in the greater environment of the maritime milieu itself. The physical boundaries found on most vessels result in close confinement and sharing of workspaces, engine-room, storage areas, passageways and other compartments with living spaces. Vessels often have a single water, ventilation or sanitation system that serves both work and living quarters.

The social structure aboard vessels is typically stratified into vessel officers or operators (ship’s master, first mate and so on) and remaining crew. Ship officers or operators are generally relatively more educated, affluent and occupationally stable. It is not uncommon to find vessels with crew members of an entirely different national or ethnic background from that of the officers or operators. Historically, maritime communities are more transient, heterogeneous and somewhat more independent than non-maritime communities. Work schedules aboard ship are often more fragmented and intermingled with non-work time than are land-based employment situations.

These are some reasons why it is difficult to describe or quantify health problems in the maritime industries, or to correctly associate problems with exposures. Data on maritime worker morbidity and mortality suffer from being incomplete and not representative of entire crews or sub-industries. Another shortfall of many data sets or information systems that report on the maritime industries is the inability to distinguish among health problems due to work, vessel or macro-environmental exposures. As with other occupations, difficulties in capturing morbidity and mortality information is most obvious with chronic disease conditions (e.g., cardiovascular disease), particularly those with a long latency (e.g., cancer).

Review of 11 years (1983 to 1993) of US maritime data demonstrated that half of all fatalities due to maritime injuries, but only 12% of non-fatal injuries, are attributed to the vessel (i.e., collision or capsizing). The remaining fatalities and non-fatal injuries are attributed to personnel (e.g., mishaps to an individual while aboard ship). Reported causes of such mortality and morbidity are described in figure 1 and figure 2 respectively. Comparable information on non-injury-related mortality and morbidity is not available.

Figure 1. Causes of leading fatal unintentional injuries attributed to personal reasons (US maritime industries 1983-1993).

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Figure 2. Causes of leading non-fatal unintentional injuries attributed to personal reasons (US maritime industries 1983-1993).

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Combined vessel and personal US maritime casualty data reveal that the highest proportion (42%) of all maritime fatalities (N = 2,559), occurred among commercial fishing vessels. The next highest were among towboats/barges (11%), freight ships (10%) and passenger vessels (10%).

Analysis of reported work-related injuries for the maritime industries shows similarities to patterns reported for the manufacturing and construction industries. Commonalities are that most injuries are due to falls, being struck, cuts and bruises or muscular strains and overuse. Caution is needed when interpreting these data, however, as there is reporting bias: acute injuries are likely to be over-represented and chronic/latent injuries, which are less obviously connected to work, under-reported.

Occupational and Environmental Hazards

Most health hazards found in the maritime setting have land-based analogs in the manufacturing, construction and agricultural industries. The difference is that the maritime environment constricts and compresses available space, forcing close proximity of potential hazards and the intermingling of living quarters and workspaces with fuel tanks, engine and propulsion areas, cargo and storage spaces.

Table 2 summaries health hazards common across different vessel types. Health hazards of particular concern with specific vessel types are highlighted in table 3. The following paragraphs of this section expand discussion of selected environmental, physical and chemical, and sanitation health hazards.

Table 2. Health hazards common across vessel types.

Hazards

Description

Examples

Mechanical

Unguarded or exposed moving objects or their parts, which strike, pinch, crush or entangle. Objects can be mechanized (e.g., fork-lift) or simple (hinged door).

Winches, pumps, fans, drive shafts, compressors, propellers, hatches, doors, booms, cranes, mooring lines, moving cargo

Electrical

Static (e.g., batteries) or active (e.g., generators) sources of electricity, their distribution system (e.g., wiring) and powered devices (e.g., motors), all of which can cause direct electrical-induced physical injury

Batteries, vessel generators, dockside electrical sources, unprotected or ungrounded electric motors (pumps, fans, etc.), exposed wiring, navigation and communication electronics

Thermal

Heat- or cold-induced injury

Steam pipes, cold storage spaces, power plant exhaust, cold- or warm-weather exposure above deck

Noise

Adverse auditory and other physiological problems due to excessive and prolonged sound energy

Vessel propulsion system, pumps, ventilation fans, winches, steam-powered devices, conveyor belts

Fall

Slips, trips and falls resulting in kinetic-energy-induced injuries

Steep ladders, deep vessel holds, missing railings, narrow gangways, elevated platforms

Chemical

Acute and chronic disease or injury resulting from exposure to organic or inorganic chemicals and heavy metals

Cleaning solvents, cargo, detergents, welding, rusting/corrosion processes, refrigerants, pesticides, fumigants

Sanitation

Disease related to unsafe water, poor food practices or improper waste disposal

Contaminated potable water, food spoilage, deteriorated vessel waste system

Biologic

Disease or illness causes by exposure to living organisms or their products

Grain dust, raw wood products, cotton bales, bulk fruit or meat, seafood products, communicable disease agents

Radiation

Injury due to non-ionizing radiation

Intense sunlight, arc welding, radar, microwave communications

Violence

Interpersonal violence

Assault, homicide, violent conflict among crew

Confined space

Toxic or anoxic injury resulting from entering an enclosed space with limited entry

Cargo holds, ballast tanks, crawl spaces, fuel tanks, boilers, storage rooms, refrigerated holds

Physical work

Health problems due to overuse, disuse or unsuitable work practices

Shovelling ice in fish tanks, moving awkward cargo in restricted spaces, handling heavy mooring lines, prolonged stationary watch standing

 

Table 3. Notable physical and chemical hazards for specific vessel types.

Vessel Types

Hazards

Tank vessels

Benzene and various hydrocarbon vapours, hydrogen sulphide off-gassing from crude oil, inert gases used in tanks to create oxygen-deficient atmosphere for explosion control, fire and explosion due to combustion of hydrocarbon products

Bulk cargo vessels

Pocketing of fumigants used on agricultural products, personnel entrapment/suffocation in loose or shifting cargo, confined space risks in conveyor or man tunnels deep in vessel, oxygen deficiency due to oxidation or fermentation of cargo

Chemical carriers

Venting of toxic gases or dusts, pressurized air or gas release, leakage of hazardous substances from cargo holds or transfer pipes, fire and explosion due to combustion of chemical cargoes

Container ships

Exposure to spills or leakage due to failed or improperly stored hazardous substances; release of agricultural inerting gases; venting from chemical or gas containers; exposure to mislabeled substances that are hazardous; explosions, fire or toxic exposures due to mixing of separate substances to form a dangerous agent (e.g., acid and sodium cyanide)

Break bulk vessels

Unsafe conditions due to shifting of cargo or improper storage; fire, explosion or toxic exposures due to mixing of incompatible cargoes; oxygen deficiency due to oxidation or fermentation of cargoes; release of refrigerant gases

Passenger ships

Contaminated potable water, unsafe food preparation and storage practices, mass evacuation concerns, acute health problems of individual passengers

Fishing vessels

Thermal hazards from refrigerated holds, oxygen deficiency due to decomposition of seafood products or use of antioxidant preservatives, release of refrigerant gases, entanglement in netting or lines, contact with dangerous or toxic fish or sea animals

 

Environmentalhazards

Arguably the most characteristic exposure defining the maritime industries is the pervasive presence of the water itself. The most variable and challenging of water environments is the open ocean. Oceans present constantly undulating surfaces, extremes of weather and hostile travel conditions, which combine to cause constant motion, turbulence and shifting surfaces and can result in vestibular disturbances (motion sickness), object instability (e.g., swinging latches and sliding gear) and the propensity to fall.

Humans have limited capability to survive unaided in open water; drowning and hypothermia are immediate threats upon immersion. Vessels serve as platforms that permit the human presence at sea. Ships and other water craft generally operate at some distance from other resources. For these reasons, vessels must dedicate a large proportion of total space to life support, fuel, structural integrity and propulsion, often at the expense of habitability, personnel safety and human factor considerations. Modern supertankers, which provide more generous human space and liveability, are an exception.

Excessive noise exposure is a prevalent problem because sound energy is readily transmitted through a vessel’s metallic structure to nearly all spaces, and limited noise attenuation materials are used. Excessive noise can be nearly continuous, with no available quiet areas. Sources of noise include the engine, propulsion system, machinery, fans, pumps and the pounding of waves on the vessel hull.

Mariners are an identified risk group for developing skin cancers, including malignant melanoma, squamous cell carcinoma and basal cell carcinoma. The increased risk is due to excess exposure to direct and water-surface-reflected ultraviolet solar radiation. Body areas of particular risk are exposed parts of the face, neck, ears and forearms.

Limited insulation, inadequate ventilation, internal sources of heat or cold (e.g., engine rooms or refrigerated spaces) and metallic surfaces all account for potential thermal stress. Thermal stress compounds physiological stress from other sources, resulting in reduced physical and cognitive performance. Thermal stress that is not adequately controlled or protected against can result in heat- or cold-induced injury.

Physical and chemical hazards

Table 3 highlights hazards unique or of particular concern to specific vessel types. Physical hazards are the most common and pervasive hazard aboard vessels of any type. Space limitations result in narrow passageways, limited clearance, steep ladders and low overheads. Confined vessel spaces means that machinery, piping, vents, conduits, tanks and so forth are squeezed in, with limited physical separation. Vessels commonly have openings that allow direct vertical access to all levels. Inner spaces below the surface deck are characterized by a combination of large holds, compact spaces and hidden compartments. Such physical structure places crew members at risk for slips, trips and falls, cuts and bruises, and being struck by moving or falling objects.

Constricted conditions result in being in close proximity to machinery, electrical lines, high-pressure tanks and hoses, and dangerously hot or cold surfaces. If unguarded or energized, contact can result in burns, abrasions, lacerations, eye damage, crushing or more serious injury.

Since vessels are basically a composite of spaces housed within a water-tight envelope, ventilation can be marginal or deficient in some spaces, creating a hazardous confined space situation. If oxygen levels are depleted or air is displaced, or if toxic gases enter these confined spaces, entry can be life threatening.

Refrigerants, fuels, solvents, cleaning agents, paints, inert gases and other chemical substances are likely to be found on any vessel. Normal ship activities, such as welding, painting and trash burning can have toxic effects. Transport vessels (e.g., freight ships, container ships and tank ships) can carry a host of biological or chemical products, many of which are toxic if inhaled, ingested or touched with the bare skin. Others can become toxic if allowed to degrade, become contaminated or mix with other agents.

Toxicity can be acute, as evidenced by dermal rashes and ocular burns, or chronic, as evidenced by neurobehavioural disorders and fertility problems or even carcinogenic. Some exposures can be immediately life-threatening. Examples of toxic chemicals carried by vessels are benzene-containing petrochemicals, acrylonitrile, butadiene, liquefied natural gas, carbon tetrachloride, chloroform, ethylene dibromide, ethylene oxide, formaldehyde solutions, nitropropane, o-toluidine and vinyl chloride.

Asbestos remains a hazard on some vessels, principally those constructed prior to the early 1970s. The thermal insulation, fire protection, durability and low cost of asbestos made this a preferred material in ship building. The primary hazard of asbestos occurs when the material becomes airborne when it is disturbed during renovations, construction or repair activities.

Sanitation and communicable disease hazards

One of the realities aboard ship is that the crew is often in close contact. In the work, recreation and living environments, crowding is often a fact of life that heightens the requirement for maintaining an effective sanitation programme. Critical areas include: berthing spaces, including toilet and shower facilities; food service and storage areas; laundry; recreation areas; and, if present, the barbershop. Pest and vermin control is also of critical importance; many of these animals can transmit disease. There are many opportunities for insects and rodents to infest a vessel, and once entrenched they are very difficult to control or eradicate, especially while underway. All vessels must have a safe and effective pest control programme. This requires training of individuals for this task, including annual refresher training.

Berthing areas must be kept free of debris, soiled laundry and perishable food. Bedding should be changed at least weekly (more often if soiled), and adequate laundry facilities for the size of the crew should be available. Food service areas must be rigorously maintained in a sanitary manner. The food service staff must receive training in proper techniques of food preparation, storage and galley sanitation, and adequate storage facilities must be provided aboard ship. The staff must adhere to recommended standards to ensure that food is prepared in a wholesome manner and is free of chemical and biological contamination. The occurrence of a food-borne disease outbreak aboard a vessel can be serious. A debilitated crew cannot carry out its duties. There may be insufficient medication to treat the crew, especially underway, and there may not be competent medical staff to care for the ill. In addition, if the ship is forced to change its destination, there may be significant economic loss to the shipping company.

The integrity and maintenance of a vessel’s potable water system is also of vital importance. Historically, water-borne outbreaks aboard ship have been the most common cause of acute disability and death among crews. Therefore, the potable water supply must come from an approved source (wherever possible) and be free from chemical and biological contamination. Where this is not possible, the vessel must have the means to effectively decontaminate the water and render it potable. A potable water system must be protected against contamination by every known source, including cross-contaminations with any non-potable liquids. The system also must be protected from chemical contamination. It must be cleaned and disinfected periodically. Filling the system with clean water containing at least 100 parts per million (ppm) of chlorine for several hours and then flushing the entire system with water containing 100 ppm chlorine is effective disinfection. The system should then be flushed with fresh potable water. A potable water supply must have at least 2 ppm residual of chlorine at all times, as documented by periodic testing.

Communicable disease transmission aboard ship is a serious potential problem. Lost work time, the cost of medical treatment and the possibility of having to evacuate crew members make this an important consideration. Besides the more common disease agents (e.g., those that cause gastroenteritis, such as Salmonella, and those that cause upper respiratory disease, such as the influenza virus), there has been a re-emergence of disease agents that were thought to be under control or eliminated from the general population. Tuberculosis, highly pathogenic strains of Escherichia coli and Streptococcus, and syphilis and gonorrhoea have reappeared in increasing incidence and/or virulence.

In addition, previously unknown or uncommon disease agents such as the HIV virus and the Ebola virus, which are not only highly resistant to treatment, but highly lethal, have appeared. It is therefore important that assessment be made of appropriate crew immunization for such diseases as polio, diphtheria, tetanus, measles, and hepatitis A and B. Additional immunizations may be required for specific potential or unique exposures, since crew members may have occasion to visit a wide variety of ports around the world and at the same time come in contact with a number of disease agents.

It is vital that crew members receive periodic training in the avoidance of contact with disease agents. The topic should include blood-borne pathogens, sexually transmitted diseases (STDs), food- and water-borne diseases, personal hygiene, symptoms of the more common communicable diseases and appropriate action by the individual on discovering these symptoms. Communicable disease outbreaks aboard ship can have a devastating effect on the vessel’s operation; they can result in a high level of illness among the crew, with the possibility of serious debilitating disease and in some cases death. In some instances, vessel diversion has been required with resultant heavy economic losses. It is in the best interest of the vessel owner to have an effective and efficient communicable disease programme.

Hazard Control and Risk Reduction

Conceptually, the principles of hazard control and risk reduction are similar to other occupational settings, and include:

  • hazard identification and characterization
  • inventory and analysis of exposures and at-risk populations
  • hazard elimination or control
  • personnel monitoring and surveillance
  • disease/injury prevention and intervention
  • programme evaluation and adjustment (see table 4).

 

Table 4. Vessel hazard control & risk-reduction.

Topics

Activities

Programme development and evaluation

Identify hazards, shipboard and dockside.
Assess nature, extent and magnitude of potential exposures.
Identify crew members at risk.
Determine suitable methods for hazard elimination or control and protection of personnel.
Develop health surveillance and reporting system.
Evaluate and follow at-risk members’ health status.
Measure programme effectiveness.
Adapt and modify programme.

Hazard identification

Inventory shipboard chemical, physical, biological, and environmental hazards, in both work and living spaces (e.g., broken railings, use and storage of cleaning agents, presence of asbestos).
Investigate hazards of cargo and those dockside.

Assessment of exposure

Understand work practices and job tasks (prescribed as well as those actually done).
Qualify and quantify exposure levels (e.g., number of hours in hazardous cargo hold areas, ambient H2S levels due to off-gassing, type of organisms in potable water, sound levels in ship’s spaces).

Personnel at risk

Review work logs, employment records and monitoring data of entire ship’s complement, both seasonal and permanent.

Hazard control and
personnel protection

Know established and recommended exposure standards (e.g., NIOSH, ILO, EU).
Eliminate hazards where possible (replace live watches in hazardous holds with remote electronic monitoring).
Control hazards that cannot be eliminated (e.g., enclose and isolate winches rather than leave exposed, and post warning signs).
Provide necessary personal protective equipment (wear toxic gas and O2 detectors when entering confined spaces).

Health surveillance

Develop health information gathering and reporting system for all injuries and illnesses (e.g., maintain a ship’s daily binnacle).

Monitor crew health

Establish occupational medical monitoring, determine performance standards, and establish fitness-for-work criteria (e.g., pre-placement and periodic pulmonary testing of crew handling grain).

Hazard control and risk reduction effectiveness

Devise and set priorities for goals (e.g., reduce shipboard falls).
Set and measure outcomes toward goals (reduce annual number of days crew members not able to work due to falls aboard ship).
Determine effectiveness of efforts in achieving goals.

Programme evolution

Modify prevention and control activities based on changing circumstances and prioritization.

 

To be effective, however, the means and methods to implement these principles must be tailored to the specific maritime arena of interest. Occupational activities are complex and take place in integrated systems (e.g., vessel operations, employee/employer associations, commerce and trade determinants). The key to prevention is to understand these systems and the context in which they take place, which requires close cooperation and interaction between all organizational levels of the maritime community, from general deck hand through vessel operators and company upper management. There are many government and regulatory interests that impact the maritime industries. Partnerships between government, regulators, management and workers are essential for meaningful programmes for improving the health and safety status of the maritime industries.

The ILO has established a number of Conventions and Recommendations relating to shipboard work, such as the Prevention of Accidents (Seafarers) Convention, 1970 (No. 134), and Recommendation, 1970 (No. 142), the Merchant Shipping (Minimum Standards) Convention, 1976 (No. 147), the Merchant Shipping (Improvement of Standards) Recommendation, 1976 (No. 155), and the Health Protection and Medical Care (Seafarers) Convention, 1987 (No. 164). The ILO has also published a Code of Practice regarding the prevention of accidents at sea (ILO 1996).

Approximately 80% of vessel casualties are attributed to human factors. Similarly, the majority of reported injury-related morbidity and mortality have human factor causes. Reduction in maritime injury and death requires successful application of principles of human factors to work and life activities aboard vessels. Successful application of human factors principles means that vessel operations, vessel engineering and design, work activities, systems and management policies are developed that integrate human anthropometrics, performance, cognition and behaviours. For example, cargo loading/unloading presents potential hazards. Human factor considerations would highlight the need for clear communication and visibility, ergonomic matching of worker to task, safe separation of workers from moving machinery and cargo and a trained workforce, well acquainted with work processes.

Prevention of chronic diseases and adverse health states with long latency periods is more problematic than injury prevention and control. Acute injury events generally have readily recognized cause-effect relationships. Also, the association of injury cause and effect with work practices and conditions is usually less complicated than for chronic diseases. Hazards, exposures and health data specific to the maritime industries are limited. In general, health surveillance systems, reporting and analyses for the maritime industries are less developed than those for many of their land-based counterparts. The limited availability of chronic or latent disease health data specific to maritime industries hinders development and application of targeted prevention and control programmes.

 

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Monday, 04 April 2011 15:31

Subways

While railroad safety comes under the jurisdiction of national governments, which issue rules and policies for safety governance and enforcement, subways are usually governed by local public authorities, which in essence govern themselves.

Subway fares usually do not cover operating cost and, through subsidies, are kept at certain levels to maintain an affordable public transportation service. Subway and other city mass transit systems make city roads more accessible and reduce the pollution associated with urban automobile traffic.

Budget cuts that have become so common in many countries in recent years also affect mass transit systems. Preventive maintenance personnel and the upgrade of tracks, signals and rolling stock are the first to be affected. The controlling authorities are often unwilling or unable to enforce their own regulatory procedures on a rapid transit system abandoned by government subsidies. Inevitably in such circumstances, a transportation accident with catastrophic loss of life during the budget cuts results in a public outcry demanding improvements in safety.

While it is recognized that great variation exists in the design, construction and age of the physical facilities of the rapid transit properties in Canada, the United States and other countries, certain standard maintenance functions must be carried out to keep operating track, aerial and underground structures, passenger stations and related facilities in the safest possible condition.

Subway Operation and Maintenance

Subways differ from railroads in several basic ways:

  • most subways run underground in tunnels
  • subways run on electricity rather than diesel or steam (although there are also some electrical trains)
  • subways run much more frequently than railroad trains
  • graffiti removal is a major problem.

 

These factors influence the degree of risk for subway train operators and maintenance crews.

Collisions between subway trains on the same track and with maintenance crews on the track are a serious problem. These collisions are controlled by proper scheduling, central communications systems to alert subway train operators of problems and signal light systems indicating when operators can proceed safely. Breakdowns in these control procedures resulting in collisions can occur due to radio communication problems, broken or improperly placed signal lights that do not give operators adequate time to stop and fatigue problems from shift work and excessive overtime, resulting in inattention.

Maintenance crews patrol the subway tracks doing repairs to tracks, signal lights and other equipment, picking up rubbish and performing other duties. They face electrical hazards from the third rail carrying the electricity to operate the subways, fire and smoke hazards from burning rubbish and possible electrical fires, inhalation hazards from steel dust and other particulates in the air from the subway wheels and rails and the hazard of being hit by subway cars. Floods in subways can also create electrical shock and fire hazards. Because of the nature of subway tunnels, many of these hazardous situations are confined-space hazards.

Adequate ventilation to remove air contaminants, proper confined-space and other emergency procedures (e.g., evacuation procedures) for fires and floods and adequate communication procedures including radios and signal lights to notify subway train operators of the presence of maintenance crews on the tracks are essential to protect these crews. There should be frequent emergency spaces along subway walls or adequate space between tracks to allow maintenance crew members to avoid passing subway cars.

Graffiti removal from both the inside and outside of subway cars is a hazard in addition to regular painting and cleaning of cars. Graffiti removers often contained strong alkalis and hazardous solvents and can be a hazard both by skin contact and inhalation. Exterior graffiti removal is done by driving the cars through a car wash where the chemicals are sprayed on the exterior of the car. The chemicals are also applied by brushing and spraying inside subway cars. Applying hazardous graffiti removers inside cars could be a confined-space hazard.

Precautions include using the least toxic chemicals possible, proper respirator protection and other personal protective equipment and proper procedures to ensure that car operators know what chemicals are being used.

 

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Monday, 04 April 2011 15:14

Rail Operations

Railroads provide a major mode of transportation around the world. Today, even with competition from road and airborne transport, rail remains an important means of land-based movement of bulk quantities of goods and materials. Railroad operations are carried out in an enormously wide variety of terrains and climates, from Arctic permafrost to equatorial jungle, from rainforest to desert. The roadbed of partly crushed stone (ballast) and track consisting of steel rails and ties of wood, concrete or steel are common to all railroads. Ties and ballast maintain the position of the rails.

The source of power used in railroad operations worldwide (steam, diesel-electric and current electricity) spans the history of development of this mode of transportation.

Administration and Train Operations

Administration and train operations create the public profile of the railroad industry. They ensure that goods move from origin to destination. Administration includes office personnel involved in business and technical functions and management. Train operations include dispatchers, rail traffic control, signal maintainers, train crews and yard workers.

Dispatchers ensure that a crew is available at the appropriate point and time. Railroads operate 24 hours per day, 7 days per week throughout the year. Rail traffic control personnel coordinate train movements. Rail traffic control is responsible for assigning track to trains in the appropriate sequence and time. This function is complicated by single sets of track that must be shared by trains moving in both directions. Since only one train can occupy a particular section of track at any time, rail traffic control must assign occupancy of the main line and sidings, in a manner that assures safety and minimizes delay.

Signals provide visual cues to train operators, as well as to drivers of road vehicles at level train crossings. For train operators, signals must provide unambiguous messages about the status of the track ahead. Signals today are used as an adjunct to rail traffic control, the latter being conducted by radio on channels received by all operating units. Signal maintainers must ensure operation of these units at all times, which can sometimes involve working alone in remote areas in all weather at any time, day or night.

Yard workers’ duties include ensuring that the rolling stock is prepared to receive cargo, which is an increasingly important function in this era of quality management. Tri-level automobile transporter cars, for example, must be cleaned prior to use and readied to accept vehicles by moving chocks to appropriate positions. The distance between levels in these cars is too short for the average male to stand upright, so that work is done in a hunched over position. Similarly, the handholds on some cars force yard workers to assume an awkward posture during shunting operations.

For long runs, a train crew operates the train between designated transfer points. A replacement crew takes over at the transfer point and continues the journey. The first crew must wait at the transfer point for another train to make the return trip. The combined trips and the wait for the return train can consume many hours.

A train trip on single track can be very fragmented, in part because of problems in scheduling, track work and the breakdown of equipment. Occasionally a crew returns home in the cab of a trailing locomotive, in the caboose (where still in use) or even by taxi or bus.

The train crew’s duties may include dropping off some cars or picking up additional ones en route. This could occur at any hour of the day or night under any imaginable weather conditions. The assembly and disassembly of trains are the sole duties of some train crews in yards.

On occasion there is a failure of one of the knuckles that couple cars together or a break in a hose that carries braking system air between cars. This necessitates investigative work by one of the train crew and repair or replacement of the defective part. The spare knuckle (about 30 kg) must be carried along the roadbed to the repair point, and the original removed and replaced. Work between cars must reflect careful planning and preparation to ensure that the train does not move during the procedure.

In mountainous areas, breakdown may occur in a tunnel. The locomotive must maintain power above idle under these conditions in order to keep the braking functional and to prevent train runaway. Running the engine in a tunnel could cause the tunnel to fill with exhaust gases (nitrogen dioxide, nitric oxide, carbon monoxide and sulphur dioxide).

Table 1 summarizes potential hazardous conditions associated with administration and train operations.

Table 1. Hazardous conditions associated with administration and train operations.

Conditions

Affected groups

Comments

Exhaust emissions

Train crew, supervisors, technical advisors

Emissions primarily include nitrogen dioxide, nitric oxide, carbon monoxide, sulphur dioxide and particulates containing polycyclic aromatic hydrocarbons (PAHs). Potential for exposure is most likely in unventilated tunnels.

Noise

Train crew, supervisors, technical advisors

In-cab noise could exceed regulated limits.

Whole-body vibration

Train crew

Structure-borne vibration transmitted through the floor and seats in the cab originates from the engine and motion along the track and over gaps between rails.

Electromagnetic fields

Train crew, signal maintainers

AC and DC fields are possible, depending on design of power unit and traction motors.

Radio-frequency fields

Users of two-way radios

Effects on humans are not fully established.

Weather

Train crew, yard workers, signal maintainers

Ultraviolet energy can cause sunburn, skin cancer and cataracts. Cold can cause cold stress and frostbite. Heat can cause heat stress.

Shiftwork

Dispatchers, rail traffic control, train crews, signal maintainers

Train crews can work irregular hours; remuneration is often based on travelling a fixed distance within a time period.

Musculoskeletal injury

Train crew, yard workers

Ankle injury can occur during disembarkment from moving equipment. Shoulder injury can occur during embarkment onto moving equipment. Injury can occur at various sites while carrying knuckles on rough terrain. Work is performed in awkward postures.

Video displays units

Management, administrative and technical staff, dispatchers, rail traffic control

Effective use of computerized workstations depends on application of visual and office ergonomic principles.

Rundown accidents

All workers

Rundown can occur when the individual stands on an active track and fails to hear approach of trains, track equipment and moving cars.

 

Maintenance of Rolling Stock and Track Equipment

Rolling stock includes locomotives and railcars. Track equipment is specialized equipment used for track patrol and maintenance, construction and rehabilitation. Depending on the size of the railroad, maintenance can range from onsite (small-scale repairs) to complete stripdown and rebuilding. Rolling stock must not fail in operation, since failure carries serious adverse safety, environmental and business consequences. If a car carries a hazardous commodity, the consequences that can arise from failure to find and repair a mechanical defect can be enormous.

Larger rail operations have running shops and centralized stripdown and rebuild facilities. Rolling stock is inspected and prepared for the trip at running shops. Minor repair is performed on both cars and locomotives.

Railcars are rigid structures that have pivot points near each end. The pivot point accepts a vertical pin located in the truck (the wheels and their support structure). The body of the car is lifted from the truck for repairs. Minor repair can involve the body of the car or attachments or brakes or other parts of the truck. Wheels may require machining on a lathe to remove flat spots.

Major repair could include removal and replacement of damaged or corroded metal sheeting or frame and abrasive blasting and repainting. It could also include removal and replacement of wooden flooring. Trucks, including wheel-axle sets and bearings, may require disassembly and rebuilding. Rehabilitation of truck castings involves build-up welding and grinding. Rebuilt wheel-axle sets require machining to true the assembly.

Locomotives are cleaned and inspected prior to each trip. The locomotive may also require mechanical service. Minor repairs include oil changes, work on brakes and servicing of the diesel engine. Removal of a truck for wheel truing or evening may also be needed. Operation of the engine may be required in order to position the locomotive inside the service building or to remove it from the building. Prior to re-entry into service the locomotive could require a load test, during which the engine is operated at full throttle. Mechanics work in close proximity to the engine during this procedure.

Major servicing could involve complete stripdown of the locomotive. The diesel engine and engine compartment, compressor, generator and traction motors require thorough degreasing and cleaning owing to heavy service and contact of fuel and lubricants with hot surfaces. Individual components may then be stripped and rebuilt.

Traction motor casings may require build-up welding. Armatures and rotors may need machining in order to remove old insulation, then be repaired and impregnated with a solution of varnish.

Track maintenance equipment includes trucks and other equipment that can operate on road and rail, as well as specialized equipment that operates only on rail. The work may include highly specialized units, such as track inspection units or rail-grinding machines, which may be “one of a kind”, even in large railroad companies. Track maintenance equipment may be serviced in garage settings or in field locations. The engines in this equipment may produce considerable exhaust emissions due to long periods between service and lack of familiarity of mechanics. This can have major pollution consequences during operation in confined spaces, such as tunnels and sheds and enclosing formations.

Table 2 summarizes potential hazardous conditions associated with maintenance of rolling stock and track equipment as well as transportation accidents.

Table 2. Hazardous conditions associated with maintenance and transportation accidents.

Conditions

Affected groups

Comments

Skin contamination with waste oils and lubricants

Diesel mechanics, traction motor mechanics

Decomposition of hydrocarbons in contact with hot surfaces can produce polycyclic aromatic hydrocarbons (PAHs).

Exhaust emissions

All workers in diesel shop, wash facility, refuelling area, load test area

Emissions primarily include nitrogen dioxide, nitric oxide, carbon monoxide, sulphur dioxide and particulates containing (PAHs). Potential for exposure most likely where exhaust emissions are confined by structures.

Welding emissions

Welders, tackers, fitters, operators of overhead cranes

Work primarily involves carbon steel; aluminium and stainless steel are possible. Emissions include shield gases and fluxes, metal fumes, ozone, nitrogen dioxide, visible and ultraviolet energy.

Brazing emissions

Electricians working on traction motors

Emission include cadmium end lead in solder.

Thermal decomposition products from coatings

Welders, tackers, fitters, grinders, operators of overhead cranes

Emissions can include carbon monoxide, inorganic pigments containing lead and other chromates, decomposition products from paint resins. PCBs may have been used prior to 1971. PCBs can form furans and dioxins when heated.

Cargo residues

Welders, fitters, tackers, grinders, mechanics, strippers

Residues reflect service in which car was used; cargoes could include heavy metal concentrates, coal, sulphur, lead ingots, etc.

Abrasive blasting dust

Abrasive blaster, bystanders

Dust can contain cargo residues, blast material, paint dust. Paint applied prior to 1971 may contain PCBs.

Solvent vapours

Painter, bystanders

Solvent vapours can be present in paint storage and mixing areas and paint booth; flammable mixtures may develop inside confined spaces, such as hoppers and tanks, during spraying.

Paint aerosols

Painter, bystanders

Paint aerosols contain sprayed paint plus diluent; solvent in droplets and vapour can form flammable mixtures; resin system can include isocyanates, epoxys, amines, peroxides and other reactive intermediates.

Confined spaces

All shop workers

Interior of some railcars, tanks and hoppers, nose of locomotive, ovens, degreasers, varnish impregnator, pits, sumps and other enclosed and partially enclosed structures

Noise

All shop workers

Noise generated by many sources and tasks can exceed regulated limits.

Hand-arm vibration

Users of powered hand tools and hand-held equipment

Vibration is transmitted through hand grips.

Electromagnetic fields

Users of electrical welding equipment

AC and DC fields are possible, depending on design of the unit.

Weather

Outside workers

Ultraviolet energy can cause sunburn, skin cancer and cataracts. Cold can cause cold stress and frostbite. Heat can cause heat stress.

Shiftwork

All workers

Crews can work irregular hours.

Musculoskeletal injury

All workers

Ankle injury can occur during disembarkment from moving equipment. Shoulder injury can occur during embarkment onto moving equipment or climbing onto cars. Work is performed in awkward posture especially when welding, burning, cutting and operating powered hand tools.

Rundown accidents

All workers

Rundown can occur when the individual stands on active track and fails to hear approach of track equipment and moving cars.

 

Maintenance of Track and Right of Way

Maintenance of track and right of way primarily involves work in the outdoor environment in conditions associated with the outdoors: sun, rain, snow, wind, cold air, hot air, blowing sand, biting and stinging insects, aggressive animals, snakes and poisonous plants.

Track and right-of-way maintenance can include track patrol, as well as the maintenance, rehabilitation and replacement of buildings and structures, track and bridges, or service functions, such as snowplowing and herbicide application, and may involve local operating units or large, specialized work gangs that deal with replacement of rails, ballast or ties. Equipment is available to almost completely mechanize each of these activities. Small-scale work, however, could involve small, powered equipment units or even be a completely manual activity.

In order to carry out maintenance of operating lines, a block of time must be available during which the work can occur. The block could become available at any time of day or night, depending on train scheduling, especially on a single-track main line. Thus, time pressure is a main consideration during this work, since the line must be returned to service at the end of the assigned block of time. Equipment must proceed to the site, the work must be completed, and the track vacated within the set period.

Ballast replacement and tie and rail replacement are complex tasks. Ballast replacement first involves removal of contaminated or deteriorated material in order to expose the track. A sled, a plow-like unit that is pulled by a locomotive, or an undercutter performs this task. The undercutter uses a continuous toothed chain to pull ballast to the side. Other equipment is used to remove and replace rail spikes or tie clips, tie plates (the metal plate on which the rail sits on the tie) and ties. Continuous rail is akin to a noodle of wet spaghetti that can flex and whip and that is easily moved vertically and laterally. Ballast is used to stabilize the rail. The ballast train delivers new ballast and pushes it into position. Labourers walk along with the train and systematically open chutes located at the bottom of the cars in order to enable ballast to flow.

After the ballast is dropped, a tamper uses hydraulic fingers to pack the ballast around and under the ties and lifts the track. A spud liner drives a metal spike into the roadbed as an anchor and moves the track into the desired position. The ballast regulator grades the ballast to establish the final contours of the roadbed and sweeps clean the surface of the ties and rails. Considerable dust is generated during ballast dumping, regulating and sweeping.

There are a variety of settings in which track work can take place—open areas, semi-enclosed areas such as cuts, and hill and cliff faces and confined spaces, such as tunnels and sheds. These have a profound influence on working conditions. Enclosed spaces, for example, will confine and concentrate exhaust emissions, ballast dust, dust from grinding, fumes from thermite welding, noise and other hazardous agents and conditions. (Thermite welding uses powdered aluminium and iron oxide. Upon ignition the aluminium burns intensely and converts the iron oxide to molten iron. The molten iron flows into the gap between the rails, welding them together end to end.)

Switching structures are associated with track. The switch contains moveable, tapered rails (points) and a wheel guide (frog). Both are manufactured from specially hardened steel containing a high level of manganese and chromium. The frog is an assembled structure containing several pieces of specially bent rail. The self-locking nuts which are used to bolt together these and other track structures may be cadmium-plated. Frogs are built up by welding and are ground during refurbishing, which can occur onsite or in shop facilities.

Bridge repainting is also an important part of right-of-way maintenance. Bridges often are situated in remote locations; this can considerably complicate provision of personal hygiene facilities which are needed to prevent contamination of individuals and the environment.

Table 3 summarizes the hazards of track and right-of-way maintenance.

Transportation Accidents

Possibly the greatest single concern in rail operations is the transportation accident. The large quantities of material that could be involved could cause serious problems of exposure of personnel and the environment. No amount of preparation for a worst-case accident is ever enough. Therefore, minimizing risk and the consequences of an accident are imperative. Transportation accidents occur for a variety of reasons: collisions at level crossings, obstruction of the track, failure of equipment and operator error.

The potential for such accidents can be minimized through conscientious and ongoing inspection and maintenance of track and right-of-way and equipment. The impact of a transportation accident involving a train carrying mixed cargo can be minimized through strategic positioning of cars that carry incompatible freight. Such strategic positioning, however, is not possible for a train hauling a single commodity. Commodities of particular concern include: pulverized coal, sulphur, liquefied petroleum (fuel) gases, heavy metal concentrates, solvents and process chemicals.

All of the groups in a rail organization are involved in transportation accidents. Rehabilitation activities can literally involve all groups working simultaneously at the same location on the site. Thus, coordination of these activities is extremely important, so that the actions of one group do not interfere with those of another.

Hazardous commodities generally remain contained during such accidents because of the attention given to crashproofing in the design of shipping containers and bulk rail cars. During an accident, the contents are removed from the damaged car by emergency response crews that represent the shipper. Equipment maintainers repair the damage to the extent possible and put the car back on the track, if possible. However, the track under the derailed car may have been destroyed. If so, repair or replacement of track occurs next, using prefabricated sections and techniques similar to those described above.

In some situations, loss of containment occurs and the contents of the car or shipping container spill onto the ground. If substances are shipped in quantities sufficient to require placarding because of transportation laws, they are readily identifiable on shipping manifests. However, highly hazardous substances that are shipped in smaller quantities than mandated for listing in a shipping manifest can escape identification and characterization for a considerable period. Containment at the site and collection of the spilled material are the responsibility of the shipper.

Railway personnel can be exposed to materials that remain in snow, soil or vegetation during rehabilitation efforts. The severity of exposure depends on the properties and quantity of the substance, the geometry of the site and weather conditions. The situation could also pose fire, explosion, reactivity and toxic hazards to humans, animals and the surrounding environment.

At some point following the accident, the site must be cleared so that the track can be put back into service. Transfer of cargo and repair of equipment and track may still be required. These activities could be dramatically complicated by the loss of containment and the presence of spilled material. Any action taken to address this type of situation requires considerable prior planning that includes input from specialized knowledgeable professionals.

Hazards and Precautions

Table 1,  table 2 and table 3 summarize the hazardous conditions associated with the various groups of workers involved in railroad operations. Table 4 summarizes the types of precautions used to control these hazardous conditions.

Table 3. Hazardous conditions associated with maintenance on track and right of way.

Condition

Affected group(s)

Comments

Exhaust emissions

All workers

Emissions include nitrogen dioxide, nitric oxide, carbon monoxide, sulphur dioxide and particulates containing polycyclic aromatic hydrocarbons (PAHs). Potential for exposure is most likely in unventilated tunnels and other circumstances where exhaust is confined by structures.

Ballast dust/spilled cargo

Track equipment operators, labourers

Depending on the source, ballast dust can contain silica (quartz), heavy metals or asbestos. Track work around operations that produce and handle bulk commodities can cause exposure to these products: coal, sulphur, heavy metal concentrates, etc.

Welding, cutting and grinding emissions

Field and shop welders

Welding primarily involves hardened steel; emissions can include shield gases and fluxes, metal fumes, ozone, nitrogen dioxide, carbon monoxide, ultraviolet and visible energy. Exposure to manganese and chromium can occur during work involving rail; cadmium may occur in plated nuts and bolts.

Abrasive blasting dust

Abrasive blaster, bystanders

Dust contains blast material and paint dust; paint likely contains lead and other chromates.

Solvent vapours

Painter, bystanders

Solvent vapours can be present in paint storage and mixing areas; flammable mixtures could develop inside enclosed spray structure during spraying.

Paint aerosols

Painter, bystanders

Paint aerosols contain sprayed paint plus diluent; solvent in droplets and vapour can form flammable mixture; resin system can include isocyanates, epoxys, amines, peroxides and other reactive intermediates.

Confined spaces

All workers

Interior of tunnels, culverts, tanks, hoppers, pits, sumps and other enclosed and partially enclosed structures

Noise

All workers

Noise generated by many sources and tasks can exceed regulated limits.

Whole-body vibration

Truck drivers, track equipment operators

Structure-borne vibration transmitted through the floor and seat in the cab originates from the engine and motion along roads and track and over gaps between rails.

Hand-arm vibration

Users of powered hand tools and hand-held equipment

Vibration transmitted through hand grips

Electromagnetic fields

Users of electrical welding equipment

AC and DC fields are possible, depending on design of the unit.

Radio-frequency fields

Users of two-way radios

Effects on humans not fully established

Weather-related

Outside workers

Ultraviolet energy can cause sunburn, skin cancer and cataracts; cold can cause cold stress and frostbite; heat can cause heat stress.

Shiftwork

All workers

Gangs work irregular hours due to problems in scheduling blocks of track time.

Musculoskeletal injury

All workers

Ankle injury during disembark from moving equipment; shoulder injury during embark onto moving equipment; work in awkward posture, especially when welding and operating powered hand tools

Rundown accident

All workers

Rundown can occur when the individual stands on active track and fails to hear approach of track equipment, trains and moving cars.

 

Table 4. Railway industry approached to controlling hazardous conditions.

Hazardous conditions

Comments/control measures

Exhaust emissions

Locomotives have no exhaust stack. Exhaust discharges vertically from the top surface. Cooling fans also located on the top of the locomotive can direct exhaust-contaminated air into the airspace of tunnels and buildings. In-cab exposure during normal transit through a tunnel does not exceed exposure limits. Exposure during stationary operations in tunnels, such as investigation of mechanical problems, rerailing of derailed cars or track repair, can considerably exceed exposure limits. Stationary operation in shops also can create significant overexposure.Track maintenance and construction equipment and heavy vehicles usually have vertical exhaust stacks. Low-level discharge or discharge through horizontal deflectors can cause overexposure. Small vehicles and portable gasoline-powered equipment discharge exhaust downward or have no stack. Proximity to these sources can cause overexposure. Control measures include:

  • extended exhaust stacks that discharge vertically
  • elimination of exhaust leaks
  • roofspace exhaust fans in buildings
  • local exhaust systems that collect exhaust at source
  • roof level fans in tunnels to boost natural airflow in the roofspace
  • catalytic converters in exhaust systems
  • not operating locomotives in buildings
  • respiratory protection: full-facepiece respirators equipped with cartridges (meeting European standards) can provide satisfactory protection under these conditions.

Noise

Control measures include:

  • cabs incorporating noise control technology
  • noise control technology installed in existing equipment during rebuilding and remanufacturing
  • personal hearing protection (consult regulations to ensure compliance during train or vehicle operation).

Whole-body vibration

Control measures include:

  • cabs incorporating vibration-control technology
  • vibration control technology installed in existing equipment during rebuilding and remanufacturing.

Electromagnetic fields

Hazard not established below present limits.

Radio-frequency fields

Hazard not established below present limits.

Weather

Control measures include:

  • work clothing that protects against cold
  • work clothing that shields against solar radiation
  • eye protection that provides protection against solar radiation
  • sunscreen lotions (seek medical advisement for prolonged use).

Shiftwork

Arrange work schedules to reflect current knowledge about circadian rhythms.

Musculoskeletal injury

Control measures include:

  • equipment designed to reflect ergonomic principles
  • training in muscle conditioning, lifting and back care
  • work practices chosen to minimize occurrence of musculoskeletal injury.

Video display units

Apply office ergonomic principles to selection and utilization of video display units.

Rundown accidents

Rail equipment is confined to the track. Unpowered rail equipment creates little noise when in motion. Natural features can block noise from powered rail equipment. Equipment noise can mask warning sound from the horn of an approaching train. During operations in rail yards, switching can occur under remote control with the result that all tracks could be live.

Control measures include:

  • track occupancy permits (TOPs) and signals to regulate movement of trains and track equipment. The TOP authorizes unique occupancy of a section of track.
  • alarms in buildings indicating movement of equipment
  • practices and procedures for safe conditions of work around track and rail equipment.

Ballast operations/ spilled cargo

Wetting ballast prior to track work eliminates dust from ballast and cargo residues. Personal and respiratory protective equipment should be provided.

Skin contamination by waste oils and lubricants

Equipment should be cleaned prior to dismantling to remove contamination. Protective clothing, gloves and/or barrier creams should be used.

Welding, cutting and brazing emissions, grinding dust

Control measures include:

  • local exhaust ventilation
  • personal protective equipment (PPE)
  • respiratory protection
  • personal hygiene measures
  • medical surveillance (depends on composition of base metal and metal in wire or rod).

Thermal decomposition products from coatings

Control measures include:

  • local exhaust ventilation
  • respiratory protection
  • personal hygiene measures
  • medical surveillance (depends on composition of the coating).

Cargo residues

Control measures include:

  • wash residues from car prior to servicing (depends on circumstances)
  • PPE (depends on circumstances)
  • respiratory protection (depends on circumstances)
  • personal hygiene measures (depends on circumstances)
  • medical surveillance (depends on cargo).

Abrasive blasting dust

Control measures include:

  • enclosed abrasive blasting facility
  • robotic blasting operation
  • dust collection system
  • PPE
  • respiratory protection
  • personal hygiene measures
  • medical surveillance (depends on abrasive, coating and cargo residue).

Solvent vapours, paint aerosols

Control measures include:

  • robotic painting system for interior of hoppers
  • low-solvent coating system
  • premixed coatings
  • piped coating transfer system
  • spray booth
  • PPE
  • respiratory protection
  • medical surveillance (depends on circumstances).

Confined spaces

Control measures include:

  • portable ventilation systems
  • PPE
  • respiratory protection.

Hand-arm vibration

Control measures include:

  • utilize tools meeting current standards for hand-arm vibration
  • vibration-absorbing gloves.

 

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" DISCLAIMER: The ILO does not take responsibility for content presented on this web portal that is presented in any language other than English, which is the language used for the initial production and peer-review of original content. Certain statistics have not been updated since the production of the 4th edition of the Encyclopaedia (1998)."

Contents

Preface
Part I. The Body
Part II. Health Care
Part III. Management & Policy
Part IV. Tools and Approaches
Part V. Psychosocial and Organizational Factors
Part VI. General Hazards
Part VII. The Environment
Part VIII. Accidents and Safety Management
Part IX. Chemicals
Part X. Industries Based on Biological Resources
Part XI. Industries Based on Natural Resources
Part XII. Chemical Industries
Part XIII. Manufacturing Industries
Part XIV. Textile and Apparel Industries
Part XV. Transport Industries
Part XVI. Construction
Part XVII. Services and Trade
Part XVIII. Guides