On June 18, 2021, at 6:30 p.m. an employee was working for a firm that operated electric power generation facilities. He was working at a natural gas-fired power plant. He and a coworker were restoring a natural gas filter system at the power plant by aligning valves after a maintenance crew had replaced filter media.
This system separates liquids from natural gas before it is burned as fuel gas to heat water and produce steam for turbines. This was Filtering Unit A. It had been taken offline for the filter media replacement. It was a model number 95V-W12A-I-18-550-WP vertical dry gas scrubber with tag number ONG01FA. Once the filter change had been completed, two draw bolts should have been tightened to 354 lb-ft (480 newton-meters) of torque. The workers were NOT aware of the manufacturer’s torque requirements. They used crescent wrenches to tighten the bolts.