Investigators with the US Chemical Safety and Hazard Investigation Board (CSB) suspect a flammable cloud that formed over two tank trucks may be the cause of a deadly flash fire at an oilfield waste recovery facility south of Houston TX which killed two workers and injured three others January 13.
"We are operating right now on the possibility that a flammable cloud formed over the two tank trucks shortly after their arrival at the site, causing what we call a 'deflagration' or flash fire of the vapor," said Carolyn Merritt, CSB chairman.
The accident occurred at the BLSR Operating Ltd petroleum storage and separation facility on Route 521 in Rosharon TX near Houston where trucks owned by T&L Lease Services, Alvin TX, were on an outdoor cleaning rack.
Lead investigator John Vorderbrueggen noted that the incident was not technically an explosion, which generally occurs in an enclosed space. In this case, the fire occurred under an open-air shed.
Eyewitnesses have confirmed that the diesel engines of the trucks began racing moments before the deflagration, indicating that flammable vapors were entering the air intakes. The fact that the truck engines were running and serving as a potential ignition source is considered to be a significant issue in this investigation.
Investigators are now focusing attention on interviewing the truck drivers, both of whom survived the accident, as well as plant employees and managers. They will also be analyzing residues of oil field waste material from the truck and the plant site to determine the source of highly flammable fumes that are suspected in the accident.
"We have located government records of other incidents in Texas and elsewhere where diesel engines revved up just before deadly fires and explosions due to the presence of flammable petroleum vapors," Merritt said. "We are concerned because of the widespread handling of oil and gas field wastes in Texas and nationwide, and our investigation will determine what further safety measures may be needed in order to prevent similar accidents in the future. In the meantime, it is important that all similar operations be aware of the potential danger of ignition from these waste products. Eliminating ignition sources during flammable waste handling operations is critical to safety."
Investigators emphasize that the diesel engine blocks did not explode, but the flash fire did destroy the cabs, tires, hoses, and other combustible truck components. Neither the waste tanks nor the fuel tanks ignited, leading investigators to believe that flammable vapors burned in a rapid hot fire. Investigators say BLSR has been cooperating with their inquiries. The CSB is an independent federal agency charged with determining root causes of chemical accidents and making recommendations to prevent their recurrence. CSB investigations generally take 6-12 months to complete, although safety alerts may be issued more rapidly as needed.