Just a split second

According to their calculations, they were too deep to find gas. But, once they had drilled into a gas zone, the operators on a drilling rig near Rocky Mountain House, Alta., had created a gas leak, causing a fire that took six hours to extinguish.

“The gas began rising to the surface from underground. It found a source of ignition on surface from the drilling rig, produced a large explosion and then flash fire,” says Scott Squires, pre-emergency planning manager at Red Deer, Alta.-based Firemaster Oilfield Services, recalling the 1998 fire. “Auxiliary equipment and tanks of flammable product that were on-site caught fire in that initial flash fire, and the fire ball went around the site.”

Flash fires pose one of the greatest health and safety risks to workers in the oil and gas industry. A sudden, intense fire that spreads through the vapours, gas or dust of an ignitable liquid, a flash fire can cause severe burns, while the larger fires caused by a flash fire often cause death and can last several hours or days.

Workers in oil and gas are exposed to the hazard of flash fire during a range of operations, including drilling, completions and well servicing, gas processing, production and SimOps (simultaneous operations).

Although the flash fire itself lasts a short duration, it can cause second- or third-degree burns to exposed skin. And due to the 1,500 F to 1,800 F heat, inhalation can damage the lungs and windpipe. The fire may also produce irritating corrosive or toxic gases.

Companies can reduce the risk of flash fires by identifying where flammable vapours are likely to accumulate. The flammable liquids that present most hazards are gasoline, raw natural gas (a hydrocarbon consisting mainly of methane) and its byproducts (ethane, pentane, propane, butane) and crude oil. Most hazardous vapours are heavier than air and collect in low or confined areas. They are also found in areas where crude oil is processed and near flammable liquid storage areas, tanks, pipes and compressors, often due to leaks from flanges, valves or gaskets.

Next, possible ignition sources must be identified. These include static electricity, lightning, welding and any hot surface.

Beth Chisholm, group lead, process safety engineering at Calgary-based Cenovus Energy, says preventing flash fires starts with an understanding of the physical properties of materials and chemicals: Are they flammable? How could they be dispersed? At what temperature do they produce vapour? At what concentration will a vapour or gas ignite?

“Supervisors and workers can manage fire hazards by preventing the release of flammable materials and by being prepared if a release occurs. At Cenovus, we ventilate our buildings to prevent flammable materials from accumulating and are able to automatically isolate equipment in case of a release,” she says.

Chisholm says supervisors must also ensure all potential ignition sources are managed.

“In accordance with the Canadian Electrical Code, we classify our facilities based on the potential for flash fires and use electrically classified equipment that is insulated to prevent ignition in areas with fire risk. One of the most often overlooked ignition sources is the hot exhaust piping of engines. It can be hot enough to ignite flammable vapours.”

Alan Royer, technical director of operations and maintenance at Edmonton-based Petroskills, says training should cover how to conduct proper isolation procedures so, if there’s an incident, workers can reduce the amount of gas released.

“You need an understanding of what is in the piping and be able to follow a pipe from, say, a vessel through buildings to where it is going — and know what type of isolation valves are in it, where they’re located and how to access them,” he says.

Personal protective equipment (PPE) is an important control against the hazard of a flash fire. PPE is designed to reduce the severity of burn injuries caused by short-term exposure to flash fires. It must be clean and free of flammable products, such as grease and oil. Coveralls, shirts, pants and jackets must be fire resistant and should be made of natural (cotton or wool) material in a plain or twill weave. Fabrics certified by the Canadian General Standards Board, in Gatineau, Que., consist entirely or primarily of Nomex, and sometimes a small amount of Kevlar.

Cenovus uses flame resistant clothing as basic PPE for all personnel in areas where there is a risk of flash fire.

“It’s important to keep sleeves rolled down and coveralls done up to achieve the best protection,” says Chisholm. “We instruct all workers to wear cotton or wool under their FRC (flame resistant clothing). Materials like polyester could melt in a flash fire and adhere to the skin, causing injury.”

Royer says workers can protect their heads and faces by wearing a hard hat and balaclava made of a fire retardant material, such as Nomex. Safety glasses should be CSA-approved. These have plastic polycarbonate lenses, are lightweight and impact resistant and may have heat resistant frames. Gloves must be fire resistant and can be made of insulated leather or polymers, such as Kevlar, Nomex and PBI, or a cotton-type material or canvas, Royer says. They should not include any nylon or polyester. Boots should be steel-toed and flame resistant (often with Nomex/Kevlar uppers). They may also have rubber outsoles that are resistant to heat and fire. Royer advises the boots also provide good ankle support to prevent spraining.

In the event of a flash fire, employers need an emergency response plan.  It must be tailored to the equipment and training levels of employees at its facilities, Squires says. Generally, he says, the main steps in a flash fire emergency response plan are:

Evacuate to a safe area.

• Notify others.

Activate alarm (to company or local fire department or industrial firefighting company).

Determine if any co-workers need medical care.

Isolate the source of the fire.

It’s important that the plan set out each step clearly, Squires adds. In an emergency, people may forget what they were trained to do.

“The adrenalin is flowing at the maximum. So, they need to have a step-by-step procedure to follow.” 

Linda Johnson is a freelance writer based in Toronto. She can be reached at [email protected].

 This article originally appeared in the August/September 2015 issue of COS.