The following are excerpts from a message delivered last week by the U.S. Chemical Safety Board’s Investigations Supervisor Don Holmstrom updating the public on the investigation of the January 12, 2009, Silver Eagle Refinery fire in Woods Cross, Utah:
”As most of you know, two refinery operators and two contractors were engulfed by the flame front and suffered serious burns. All four were hospitalized and are now recovering.
” To date, our investigation has found that on the evening of January 12, 2009 at approximately 5:20 pm a large vapor cloud was released from an atmospheric storage tank, known as tank 105, which contained an estimated 440,000 gallons of light naphtha.
”Through an examination of the damage to the area surrounding the tank the CSB has determined that the vapor cloud found an ignition source - for example a utility room with a gas heater or an electrical outlet connected to a conventional refrigerator - and the ensuing flash fire spread up to 230 feet west of the tank farm.
”Two structures were damaged as a result of this fire, a shed and a lab facility located approximately 140 feet and 160 feet respectively, from the site of the release.
”On the day of the incident, tank 105 was receiving up to three different streams of hydrocarbon liquids from the refinery, including 'light' or low-boiling substances. The primary feed into tank 105 had been sent from the #1 crude unit pre-flash accumulator for approximately three weeks prior to the incident. Feeding tank 105 directly from this unit was a recent process change and the feed from this unit had undergone a different form of processing. Workers were also purging equipment with nitrogen to remove flammable liquid, with the intent to pressure the liquid into tank 105.
”The CSB is investigating reports from plant personnel indicating a history of vapor leaks from tank 105 both prior to and following tank repairs.
”The CSB will be investigating if the floating roof on tank 105 was equipped with the appropriate seal for use in the storage of light hydrocarbons of the type sent to the tank. Our investigation will examine possible failures within tank 105 such as gaps between the seal and the inner tank wall, the integrity of the seal, and the design and structural integrity of the tank.
”Currently the CSB has identified two additional issues that are of particular interest to our ongoing investigation. The first is an examination of changes to the process unit sending liquid to tank 105 and possible effects that these changes had on the incident.
”We will also review facility siting issues relating to this release and fire. Specifically, the occupied lab was affected by the flash fire. This structure is located in close proximity to operating process units.
”The CSB's investigation into the March, 2005 explosion and fire at BP Texas City examined facility siting of portable work trailers. All of the 15 contract workers killed in that incident had been working in or near portable trailers located near hazardous process equipment.
”As a result of our findings, the CSB issued an urgent recommendation to the American Petroleum Institute to update their guidelines for portable work buildings such as trailers.
Today, the CSB investigative team is returning to Washington, D.C. to brief agency officials and analyze the information we have gathered during our visit to the site. Depending on the course of the investigation, we expect to return periodically to Woods Cross to gather more information.”