Working safely in and around storage tanks

Storage tanks of a variety of shapes and sizes can be found in all sorts of industries. While we typically associate storage tanks with refineries and other petrochemical-related facilities, you’ll see them at nearly every type of production facility. They may hold diesel fuel for a company’s vehicles, purified water for food processing, plastic pellets for injection molding, or chemicals used to clean or treat products and equipment.

Although storage tanks are common and their design fairly simple, they can quickly become complicated when it’s time to perform maintenance on them. Perfuming work inside or on storage tanks can expose workers to flammable, explosive, and toxic chemicals. The interiors of tanks are usually considered to be confined spaces, with all the challenges and complexities that creates. But safety in and around tanks is a serious business, especially given the number of fatalities that have resulted. According to the Chemical Safety and Hazard Investigation Board, more than 60 workers have died since 1990 while performing hot work projects on storage tanks, and since 1982, the National Institute for Occupational Safety and Health has recorded 160 fatalities related to confined spaces.

Associated hazards

As noted, most tanks qualify as confined spaces that are not regularly occupied, creating issues related to entry and exit, ventilation, lighting, and exposure to potential contaminants. That generally makes them permit-required spaces and requires safety staff to develop a specific safety plan.

Additional challenges of storage tanks relate to the materials that are stored in them, which may be flammable, explosive, or toxic to workers. Even after the contents of the tanks have been emptied, dangerous vapors and fumes may remain. Because the interior of tanks isn’t designed for regular occupancy, there’s the potential for slips and falls. When tanks are being cleaned, the cleaning techniques and materials may also present safety challenges.

Hot work challenges

Because many substances stored in tanks are flammable or emit potentially flammable vapors, hot work projects such as welding, brazing, or cutting require additional caution. If there are reasonable alternatives that don’t involve hot work, those should be considered first.

Before beginning hot work in, on, or around a storage tank, the safety professional should conduct an assessment to identify potential hazards and determine measures that will be taken to mitigate them. That may include atmospheric monitoring to ensure there are no combustible vapors in the area. Even if the tank’s contents have been properly drained or purged, it’s advisable to inspect and even test to ensure that flammable materials aren’t present.

Before work begins

When approaching repairs or other work to storage tanks, planning is essential. The first consideration is what has been stored in the tanks, because the contents may create a hazardous atmosphere.  Even though the tank has been drained, it’s possible that some of the stored material is still on the tank floor or walls, or that vapors from the contents are present.

Before any work begins, workers should verify that the tank has been locked out or isolated from other systems and that adequate ventilation is in place and working properly. The tank should be inspected to ensure that the walls, floor, and roof are structurally sound and that any supports don’t show any physical defects. If the tank has a floating roof, that must be secured safely. Attention must also be paid to the area surrounding the tank, because it may present other hazards or complicate a rescue should one become necessary.

Cleaning tanks

It’s not unusual for storage tanks to develop debris or sludge over time, resulting from contaminants or corrosion. Those unwanted materials can affect the materials stored in the tanks and interfere with pumps and pipes, so it may become necessary to drain and clean the tanks periodically. Tanks may also need to be drained and cleaned in preparation for a change to a new material, or when they’re due for any required inspections.

Maintenance personnel typically are responsible for cleaning a wide variety of settings and equipment, so it may seem natural to expect them to handle cleaning the tanks. However, cleaning tanks requires specialized training and expertise, and employees who lack that training should not be permitted to work on them.

Cleaning tanks safely requires a series of steps, including confined space procedures. Piping, valves, manholes, and other elements of the system must be double-checked to verify they’re in the correct settings. Workers must wear the correct PPE for both the nature of the task and the materials stored in the tank, particularly if the contents may be corrosive or toxic. When needed, gas and oxygen detectors should be used and specialized safety equipment such as harnesses should be on hand.

The best and safest approach to cleaning tanks is often to outsource the work to firms that specialize in the process. While that may carry a slightly higher cost than using a company’s own staff, it dramatically reduces the possibility of serious injuries or other problems — and incidents involving tanks can be catastrophic.

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