Welding blamed for 2008 cardboard mill blast
Volume 25, No. 2
A safety bulletin released by the U.S. Chemical Safety Board warns of the hazards of conducting hot work in a variety of industries and identifies seven key lessons aimed at preventing worker deaths during hot work in and around storage tanks containing flammable materials.
Hot work is defined as any work activity that involves burning, welding, cutting, brazing, grinding, soldering or similar spark-producing operations that can ignite a flammable atmosphere.
The CSB began investigating hot work hazards following an explosion that occurred on July 29, 2008, at the Packaging Corporation of America (PCA) corrugated cardboard mill in Tomahawk, Wisconsin, which killed three maintenance workers and injured another. The CSB determined the explosion resulted from welding above an 80-foot-tall storage tank that contained highly flammable hydrogen gas - the product of bacterial decomposition of organic fiber waste inside the tank.
At the time of the accident, PCA did not recognize waste fiber tanks as potentially hazardous or require combustible gas monitoring prior to welding nearby. PCA, which fully cooperated with the CSB investigation, subse-quently developed new company standards requiring gas monitoring before any hot work.
"Hot work around flammable gas or vapor is one of the most common causes of worker deaths that we see at the Chemical Safety Board," said CSB Board Member William B. Wark. "Tragically, most of these accidents are readily preventable with better hazard assessments, proper gas monitoring and other straightforward safety measures."
In the ten months following the explosion at PCA, the CSB deployed investigators to five other sites where hot work ignited flammable gas or vapor, including an explosion at an oil facility in La Rue, Ohio, that killed two contractors in October 2008; an explosion that killed one and injured another at a used oil plant in Miami, Florida, in December 2008; an explosion that killed a contract welder at a food processing plant in Boardman, Oregon, in February 2009; an explosion at a produce facility in Atwater, California, in March 2009 that severely burned two employees; and the explosion of a massive gasoline storage tank that killed three workers in Garner, Arkansas, in May 2009.
The CSB also collected information from the Honolulu Fire Department about a fatal hot work explosion at a waste oil company in October 2008 and noted findings from previous major hot work explosions in Pennsylvania, Delaware, Florida and Mississippi that were investigated by the CSB or the U.S. Environmental Protection Agency.
"Companies need to develop comprehensive systems for controlling the hazards of hot work where flammable vapor could be present," said CSB Investigations Supervisor Don Holmstrom, who led the investigations. "Regulators, companies and workers should recognize that combustible gas monitoring will save lives. A common feature of virtually all these accidents is the failure to recognize all the locations where a flammable atmosphere could be present. The absence of flammables needs to be verified before and during any hot work."
Combustible gas monitors are handheld electronic instruments that measure the amount of flammable material in the atmosphere, expressed as a percentage of the lower explosive limit. Proper training and calibration are essential for using gas monitors effectively.
The safety bulletin, entitled "Seven Key Lessons to Prevent Worker Deaths During Hot Work In and Around Tanks," notes that the CSB has identified over 60 fatalities since 1990 due to explosions and fires from hot work activities on tanks.? Holmstrom said those accidents have continued to occur since May 2009, the date of the last explosion covered in the bulletin.
Industries where hot work explosions have occurred include food processing, pulp and paper manufacturing, oil production and recycling, waste treatment, fuel storage and distribution.
"OSHA (the Occupational Safety and Health Administration) does not require combustible gas monitoring for hot work on or near flammable storage tanks,"? Holmstrom said. "As our investigation continues, our team will be looking into this issue and we will comment on it in our final report."
The CSB has produced two computer-animated safety videos on hot work accidents investigated by the CSB. "Death in the Oilfield" is about an explosion in Mississippi that killed three workers in 2006, and "Public Worker Safety," concerning an explosion at a wastewater treatment plant in Daytona Beach, Florida, that killed two workers, also in 2006. These may be viewed at www.csb.gov (Video Room) or on YouTube. The CSB distributes a two-DVD set of CSB safety videos free to anyone who orders through the web site?
A comprehensive safety video on the dangers of hot work - based on the new safety bulletin - is in production and is expected to be released within approximately a month, said CSB Director of Public Affairs Dr. Daniel Horowitz.
The CSB investigation of the explosion at PCA remains ongoing.