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CSB illustrates events leading to 2016 refinery fire

Operators followed accepted practice

Posted July 28, 2017

The U.S. Chemical Safety Board (CSB) released a new animated video to describe the events leading to a November 22, 2016, fire at a Louisiana refinery. The fire, which erupted during maintenance activities at the refinery’s sulfuric acid alkylation unit, severely burned four workers.

According to the CSB, the 2016 incident occurred when operators attempted to open a valve on a spare isobutane pump in order to put the pump into service. The valve was manually operated by a handwheel that was connected to a gearbox that contained gears used to open and close the valve. However, the gearbox was not working properly and would not open the valve. The operators followed the accepted practice of removing the gearbox and its support bracket from the valve.

What the operators didn’t know was that the valve was one of three percent of the valves in the alkylation unit that were of an older design. This design used bolts to connect the gearbox and its support bracket to the valve and also secured a critical piece of pressure-containing equipment called the top-cap. When removed, the bolts left the top-cap disconnected and the valve vulnerable to pressure.

At this point, the operators attempted to open the valve using a pipe wrench. With the bolts and gearbox removed and the top-cap not secured, the valve immediately failed and came apart. Pressurized isobutane escaped from the valve and formed a flammable vapor cloud. CSB says the vapor cloud likely found an energized welding machine approximately 70 feet away from the initial release, and ignited. The resulting fire seriously injured one refinery employee and three contractors who were working in the area.

The three-minute animation is available on the CSB’s website.

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