DERIDDER, Louisiana (From the Leesville Daily Leader) -- The U.S. Chemical Safety Board (C.S.B.) has provided a status-update for the February 8th explosion at the Packaging Corporation of America (P.C.A.) facility in DeRidder.
On the day of the explosion, which resulted in three deaths and seven injuries, Sgt. James Anderson, State Police Troop D spokesman, said welding activity was taking place near the tank that exploded. The tank contained "a foul condensate, which is a by-product of the cooking process," he said.
A three-person investigative team from the C.S.B. in Washington, D.C. deployed to the scene at P.C.A.
"The C.S.B. has investigated many hot work accidents across the country, including a 2008 explosion that killed three workers at a different P.C.A. plant in Tomahawk, Wisconsin." said Chairperson Vanessa Sutherland. "Hot work incidents are one of the most common causes of worker deaths we see at the C.S.B., but also one of the most readily preventable."
Chief Deputy Joe Toler, Beauregard Parish Sheriff's Office, and Deputy Chief Brant Thompson, State Fire Marshall's Office, both confirmed there was no fire to be put out at the site of the explosion. The issue was initially believed to be related to pressurization in the tank.
The investigator-in-charge from the Western Regional Office of the C.S.B, Jerad Denton, is handling the P.C.A. investigation. He said, "Preliminary results show the 30-foot-tall tank that exploded on February 8th had been left with about 10-feet of water in it. This left 20-feet of vapor space."
The liquid in the tank is primarily water, but other materials, some of which are flammable, also exist in the vapor space. "P.C.A. decided to leave 10-feet of foul condensate (mainly water, but also methanol, hydrogen sulfide, turpentine, and other sulfur components) in the tank because there was no work being performed on the tank and resources were being used for the mill's annual outage," said Denton.
Workers above the tank were doing some welding. Welding is one of several types of "hot work," or spark-producing operations that can ignite fires or explosions. Most hot work incidents result in the ignition of combustible materials, or the ignition of structures or debris near the hot work.
It appears that a spark from the welding flashed into the tank, which caused combustion, and resulted in lift-off of the tank, said Denton.
The mill has different processing areas for creating paper pulp. The tank left one processing area and landed in another one. "When we arrived we found the tank had launched about 400-feet away," he said.
The tank is designed not to pull in air. But the investigators believe air was, indeed, pulled into the tank.
Denton said this aspect of the situation is still under investigation, "however, there are pressure-relief valves on the tank that can pull in air if the tank begins pulling a vacuum. Additionally, there are overflow lines on the tank that require a water seal between air in the atmosphere and vapor inside the tank. If this water seal is lost, there is nothing preventing air from entering the tank. There are also other units/vessels that are connected to the tank that could have potentially pulled in air."
At the time of the incident, there were no safety measures in place to prevent this sort of event. Currently, P.C.A. is working to address these issues. The C.S.B. has discussed the possibility of having P.C.A. conduct a process-hazard-analysis on the tank and connected equipment, said Denton. "Such an analysis would provide P.C.A. with the opportunity to identify, evaluate, and control process hazards associated with this tank including ensuring the vapor space inside the tank stays outside of its explosive range and preventing hot work tasks, like welding, from starting when a nearby unit/vessel contains material in an explosive range."
The C.S.B. is currently in the report-writing phase of this investigation. Once the process is finalized, the report will be open for the public to view on their website.