Forgotten LPG Tank Explodes, Burns
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Photo by John Carroll, Dade Co. Fire Public Information Office
An abandoned and supposedly purged 2000-gallon LPG tank presented the Metropolitan Dade County, Fla., Fire Department with a potentially dangerous situation.
Responding at 10:24 p.m. last Jan. 29 to a reported explosion and fire at a scrap aluminum yard in an unincorporated area near Miami, first-arriving units found a jet-like flame rising 60 feet. Later they would discover that the old tank was still interconnected with two other 2000-gallon aboveground LPG tanks which had been filled earlier in the day. This time the old tank failed.
Ignition of the leaking gas was thought to be from the pilot flame of a propane liquid evaporator adjacent to a large aluminum-melting furnace.
The initial response included Engines 2 and 35, Rescues 2 and 35, Aerial 17, Battalion Chief 5 and Operations Chief 3. Two fence gates were forced to gain access to the yard. Up close, they found that a valve or gaging device had apparently blown off the underground tank, leaving a 1 1/8-inch open flange from which the gas was escaping and burning. A large manhole cover was also found nearby.
The battalion chief ordered Engine 2 to advance two 1 1/2-inch preconnected lines to the tank to protect exposures and possibly personnel if a plugging procedure was decided upon later. Personnel from Rescue 2 managed to close a valve controlling the liquid portion of the tank, and the flame was reduced somewhat. Engine 35 laid a 3-inch supply line to Engine 2 from a hydrant 600 feet away.
The incident was to last throughout the night and most of the following day.
A command post was set up outside the plant yard by the operations chief. He ordered a search of the complex for other tanks or valves, which were closed when found.
Capping or plugging the leak at the tank was first considered by the chief as the most direct tact. However, after consultation with plant and gas company personnel, it was determined that burning off the contents of the tank was the best procedure to follow. How much liquid propane remained in the leaking tank was not known.
Water increased burning
The rate of burning off the gas would be accelerated, gas company personnel advised, if water could be introduced into the tank. In contact with the supercold and self-refrigerating LPG, water would add relative heat and increase its boiling rate.
To add the water, fire fighters attached copper tubing to a small diameter water hose and placed the end of the tubing into the open flange. When the water reached the liquefied gas, vapor production and flame size were greatly increased. But then concern was raised that the increased radiant heat might damage exposed materials and equipment.
Directing protective hose streams on exposures proved to be inappropriate because the large quantities of run-off water ran directly into the open manhole of the leaking tank. If it extinguished the flame, an uncontrolled heavierthan-air vapor cloud could be released. If the cloud then found another ignition source, another explosion would occur.
Discontinued water
The practice of adding water to the tank for accelerated burning was discontinued. Although it took many hours, the remaining product burned off without incident.
From this chain of events it can be seen that officers in charge of unique incidents involving a hazardous substance must obtain as much information as possible before reacing a decision on how to best handle the situation.
Armed with information and suggestions from plant and gas company personnel, the officer in charge here developed a plan for controlling the fire, yet remained flexible to deal with a new situation. There were no injuries or significant property loss except for the escaping gas.
