Propane Emergencies: Managing Dangerous Incidents Involving Propane.

Posted: June 17, 2017 in Uncategorized

Have you ever thought about how many propane tanks are located in your response area? Considering propane tanks supply LPG to barbecue grills, food trucks, forklifts, heaters, cars, buses, sanitation trucks, RV’s, and handheld propane torches, there may be hundreds of propane cylinders in your response district. Small 20 lb tanks are commonly used for gas grills on residential properties, while larger LPG storage tanks are located at commercial businesses, hardware stores, gas stations, industrial areas, and underground.

Every firefighter should be familiar with the dangers or propane, NOT just company officers and members of the hazmat team. The nozzleman on the engine company is the one who is closest to burning vehicles, dumpsters, and buildings. It’s especially important for the urban fireman to become familiar with the properties of propane, and how to deal with leaks vs fires involving tanks and cylinders.

What is propane?

Propane and butane are the two major LPG gases extracted and used in the gas industry. About 70% of propane is processed from natural gas. Propane is colorless and odorless in its natural state, but a commercial odorant is added so it can be detected if it leaks. The most common used odorant is ethyl mercaptan.

LP-gases belong to a family of chemical compounds known as alkane hydrocarbons, meaning they are made up of hydrogen and carbon atoms only. Propane is 1.5 times heavier than air. The combustible materials in propane are carbon and hydrogen (hydrocarbons). The oxygen needed to burn propane vapor is obtained from the air. Air is made up of 20% oxygen, 79% nitrogen and 1% other gases. Any ignition source must provide enough heat to the mixture of fuel and oxygen to raise the temperature of the propane to its ignition temperature, which is between 920°F and 1,120°F. The flammable limits (explosive range) for propane: LEL 2.15% UEL 9.60%

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When responding to a reported LPG barbecue grill fire involving a propane tank, the initial company officers concerns should be exposures, and the possibility of a BLEVE. Upon arrival, try to determine what’s burning, where it’s burning, whether the relief valve has activated, exposure issues, and the size of the tank. This will help determine the initial actions on apparatus placement, strategy and tactics. The gas grill fire may turn out to be a grease fire or food burning with no threat to the propane tank. It’s possible the hose leading to the tank regulator may be burning and the flame is being fed by the propane from the tank. These can easily be handled by extinguishing the fire with an ABC fire extinguisher, water can, removing the oxygen by closing the lid of the grill, or closing the cylinder valve supplying the tank (righty-tighty). Stretch a handline to protect exposures such as exterior siding, overhead awnings, or a deck. Use a 30° fog pattern in the vapor space of the propane tank if the cylinder is threatened by flame impingement.

REMEMBER: Never extinguish an unisolated pressure fed flammable gas fire unless the fuel source can be isolated. Leaking gas can migrate away from the container and may find another ignition source.

If there’s no fire visible and it’s only an LPG leak (detected by smell of ethyl mercaptan odorant) eliminate any sources of ignition (pilot burner, cigarettes, lighter, electric motors, switches, flares, static discharges, cell phones) evacuate the area, and ventilate nearby structures using PPV. Use a CGI (Combustible Gas Indicators) to determine the level of flammable vapors in the area, determine the source, and control the release. Take readings in nearby structures and basements as a precaution. REMEMBER: Propane is heavier than air and will settle in low areas. (Propane vapor density is 1.52 at 60°F.)

TIP: Propane flammable range is 2.15 – 9.60. Each cubic foot of liquid propane will boil off 270 cubic feet of propane vapor.

Any decision to approach a propane tank showing direct flame impingement on its vapor space must be made on a case-by-case basis after evaluating the hazards and risks, and determining if an adequate water supply has been established. If you arrive to hear a jet engine sound, evacuate the area, stretch a line, and prepare to take cover. The relief valve has activated and a high pressure flame should be visible. Most likely the cylinder valve connection is cross-threaded or leaking. Any flame impingement on the vapor space will heat the propane tanks shell; the tank will have to be cooled to prevent a BLEVE. From a safe area such as the corner of the home or a garage, wearing full PPE, cool the cylinder with a line before approaching to shutoff the flow of propane gas, or play it safe and just cool the tank and let the LPG burn off. Again, decisions must be made on a case-by-case basis as tanks can fail within minutes of direct flame impingement.

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Firefighters should be aware that a functioning PRV (Pressure Relief Valve) on a burning propane tank is not a reliable indication that the tank is safe to approach or a reliable indicator of when or if the tank may fail.

TIP: A propane tank contains liquid and vapor. Fire heats the tank shell in the vapor space area more rapidly than the liquid area.  By the time steel reaches 1,800°F it has lost 90% of its strength. A propane tank will eventually relieve pressure either through a split in the tank in form of a jet flame, or the container fails. In most cases, the PRV will function early in the fire. If the valve handle has melted away, a pair of vise grips can be used to shut the valve, BUT it would be much safer to just let the gas burn off while cooling the tank from a safe distance.

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This propane tank fire was caused by a cross threaded hose connection. The leaking gas caught fire and raged around the tank outlet. The tank was connected to a grill that was up against the home causing the siding to melt. An 1 3/4 hoseline with a fog nozzle should be used to go back and forth cooling the tank and extinguishing the exposed siding of the house until a second line is in service. If upon arrival to a gas grill propane tank fire with exposure to the home you notice the relief valve is activated and the jet engine sound is present, KEEP BACK a good distance and cool the tank from an area of protection such as the side of a house, behind a garage or large vehicle. If the home is starting to catch fire, go for a 2 1/2 line for more reach from the safer distance. Upgrade the incident to a full structure assignment and request Hazmat response.

TACTICAL OBJECTIVES: The primary tactical objective is to cool the outside of the portable cylinder protecting the shell and reduce the pressure to the point that the pressure relief valve closes and the cylinder valve can be manually closed. The secondary objective is to protect exposures, extinguish any structure fires, check for extension, and monitor nearby structures for propane gas.

TIP: Propane pressure regulators are designed to control propane vapor pressure. They reduce the higher gas vapor pressure inside the storage container to a lower and more constant pressure, which is necessary to operate gas appliances like heaters, stoves, safely and efficiently. NFPA 58 requires the use of two-stage regulator systems for most fixed installations in buildings. NFPA also requires that all 20lb cylinders be equipped with an OPD (Overfill Protection Device).

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Vehicles: Propane is often transported via railcars and delivery trucks. Other vehicle uses are LPG vehicles, forklifts, buses, food trucks, and RV’s. LPG powered passenger vehicles must have their PRV’s vented to the outside of the vehicle. They are required by NFPA 58 to be identified with a diamond shaped label on the lower right rear of the vehicle with the letters “PROPANE” on the silver or white reflective badging.

First arriving officers should immediately suspect and be aware of propane tanks on RV’s, forklifts, and food trucks. Transport trucks with large storage tanks are obvious, and LPG passenger vehicles have badging placards on the back (pic above). Some vehicles could have 20 lb LPG tanks located in the trunk, or in the bed of pickup trucks. Unsuspecting firemen may be approaching a dangerous situation if they’re not aware of hidden propane tanks being heated during a vehicle fire. One sign is an activated relief valve or pressurized flame with a loud jet engine sound. Like any modern day vehicle fire, be cautious when approaching vehicle fires. If the occupant is present, ask him/her if there are any gasoline/propane tanks or any other hazardous materials in the trunk.

If called to investigate an odor of propane gas in a parking garage or parking lot, check to see if there are any LPG vehicles. Once identified, use CGI’s to investigate the source and obtain readings. Evacuate people from the area, control ignition sources, identify the source of the leaking propane, and stop the leak if it can safely be done. The fuel tank will usually be in the trunk and will need to be opened to access the tank valves and fittings. DISCONNECT THE BATTERY before you open the trunk. The contact switch for the truck light is a potential source of ignition.

If the LPG powered vehicle is heavily involved in fire, prepare for a possible BLEVE. Evacuate the area, request police for traffic control and from a maximum and safe distance, protect any exposures from the vehicle fire or pressurized flame coming from the vehicle (although rare, the PRV can fail). When the PRV is properly activated, it should not be an indicator that a BLEVE will not occur. After a risk/benefit analysis, unless there’s an occupant trapped in the burning vehicle or in immediate danger, let the LPG burn off; the vehicle can be replaced.

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How many times during an entire career will the average firefighter respond to a propane leak or fire involving a forklift? These are extremely rare incidents, but they do happen. First arriving crews must quickly and carefully determine whether or not the propane tank is involved, rescue priorities, exposure problems, evacuation, and requesting additional resources if needed.

Forklifts are powered by motor fuel service propane cylinders that are usually configured to supply liquid propane to the engine rather than the vapor. They can have as many as five openings in the service end of the cylinder. Fittings may be threaded or flanged. Each service valve opening is marked for either vapor or liquid service. Most cylinders are equipped with a PRV (Pressure Relief Valve) set to function at 375 psi. If the forklift is on fire and the tank is threatened by heat or flame exposure, stretch two handlines and cool the tank while extinguishing any fire involving the forklift. Wet any exposure combustibles if necessary. Keep a safe distance, evacuate any workers nearby and let the LPG burn off while cooling tank from maximum distance. Extinguish the fire involving the forklift (NOT THE TANK!) and apply a 30° fog at the vapor space for several minutes before making any decision to approach and close the tank supply. Contact the local propane marketer for technical assistance in removing and disposing the cylinder.

TIP: Motor fuel cylinders can rupture under fire conditions even if the PRV (Pressure Relief Valve) is not functioning.

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Dumped Tanks: In urban areas, 20 lb propane cylinders are often dumped in alleys, dumpsters and vacant lots. Be suspect of tanks or disposed cylinders in dumpsters, garages, sheds, and even basements during structure fires. These tanks were discovered under a trailer behind a block away from the fire station.

Firefighters arriving to a dumpster fire should assume that hazardous materials may be present and approach with caution. If you hear hissing sounds coming from a well-involved commercial dumpster, it might be a relief valve blowing off. Although propane emergencies and BLEVE’s are rare, preparing for them by being proactive can save firefighters from injuries.

Close Call: Watch Propane Explosion During Fire In Maine-Click Here.

This explosion engulfed a forklift with the operator barely escaping with his life. See the full story and more video at The Blaze.

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Above: The first due engine found a fully involved fire in a camper trailer with propane tanks venting and fire extending to the garage. Firemen were able to quickly control fire and extinguish the fire approximately 20 minutes after arrival. Quick action by fire department personnel prevented the fire from extending to the residence, and the possibility of an explosion of the propane tanks.

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Be careful when approaching a fire involving an RV. The propane tanks can be anywhere, including under the vehicle. Use caution and locate them to see if the relief valve has activated, or fire is threatening the tanks.

DO NOT always assume that the activation of a relief valve will prevent a BLEVE. See VIDEO here.

Sources: Propane Emergencies 3rd Edition  UrbanFireTraining

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