PLAN AHEAD TO PREVENT A DISASTER
BY J. Wm. SNODGRASS, JR., CFI, CEFI, CFII, Battalion Captain, Special Investigation Unit, Jackson Township (OH) Fire Department
At 1433 on Monday, July 8, 1996, we responded to a flash fire with explosions at Ferrellgas, a liquefied petroleum gas (LPG) distribution company. The building, constructed of steel and aluminum sheeting and a built-up foundation of block and concrete slab floor, was used for repairing, refilling, and shipping full and empty propane cylinders. At the time of the fire/explosion, 32,678 gallons of liquid petroleum gas were on-site. As a result of the fire/explosion, 6,470 gallons were lost. Next door to Ferrellgas was Suburban Propane, another LPG distribution company, which had 46,162 gallons of liquid petroleum gas on-site. In addition, three rail cars, carrying 58,000 gallons of LPG, were on the rail siding directly behind this location.
The fire set off a series of chain reactions that resulted in the destruction of the Ferrellgas structure and its contents and caused major damage to another building, vehicles, and tanks on Ferrellgas property. In addition, radiant heat and flying debris from exploding tanks became airborne, extensively damaging adjacent properties and vehicles.
A six-block area was evacuated. The fire was upgraded to a second alarm that brought mutual aid from six area fire departments. A defensive mode was implemented. Un-manned monitor nozzles were used to protect the two 30,000-gallon bulk tanks at the fire site, avoiding a boiling liquid-expanding vapor explosion (BLEVE). The fire was brought under control at 1637 hours, but equipment remained on-site for 24 hours and 13 minutes. Five structures and 19 vehicles–all within a 500-foot radius of the main fire zone–were damaged or de-stroyed. Three of the four employees at the site at the time of the fire/explosion were injured.
CAUSE
The fire`s point of origin was determined to be in the southeast corner of the back of the Ferrellgas structure, where the cylinders were filled. The area contained eight scales. At the time of the incident, six scales were in use; two were not plumbed into the main liquid propane gas manifold used for filling. A tank exploded on one of the scales (the point of origin) and was forced down into the scale, further rupturing it. When the tank went down into the scale, two of the mechanical arms went through the plate of the scale and into the cylinder, puncturing it. The scale arm was found approximately 30 feet south of the building.
The fire/explosion resulted from the bleeding of the propane gas into the atmosphere from the cylinder during the filling process. The most probable cause of ignition was static electricity from an undetermined source. The humidity level at the time of the fire was 32 percent, as reported by the U.S. Weather Bureau. A low relative humidity (about 30 percent or less) dries out materials and makes them good insulators, making static accumulations more likely.
Many commonly encountered materials not usually considered to be electrical conductors contain certain amounts of moisture in equilibrium with the surrounding atmosphere. The electrical conductivity of these materials increases in proportion to the moisture content of the material, which depends on the relative humidity of the surrounding atmosphere.
PREVENTION
Although the main contributing factor to this fire was an atmospheric condition no one can control, the fire department can act to shift the odds in favor of preventing a disaster. Prevention bureau personnel should review the codes and be totally prepared when making on-site inspections. If the local code does not ensure safe operations at a site, perhaps these personnel should look to National Fire Protection Association standards or state/federal Occupational Safety and Health Administration regulations. In addition, when making on-site inspections at occupancies in which LPG is stored or used, inspectors should do the following:
Ensure that no liquid or vapor LPG is discharged into the atmosphere, particularly inside a structure.
Ensure that any enclosure in which LPG is transferred has an explosionproof ventilation system capable of removing any pockets of vapor.
Ensure that employees are wearing appropriate clothing and shoes that do not create static electricity.
Ensure that employees are properly trained to perform their functions and know all emergency procedures for shutdown.
Ensure that all electric appliances in the area are explosionproof and properly maintained.
Training and preplanning are essential for successfully mitigating incidents of this type. Be proactive. Don`t let a disaster happen in your community. n
