The U.S. Chemical Safety and Hazard Investigation Board announced Wednesday that the cause of the PES Refinery explosion in June was a ruptured pipe elbow in the refinery’s alkylation unit. According to officials from the CSB, the pipe elbow had a thickness of .012 inches – about half the width of a credit card – and hadn’t been inspected for corrosion in 45 years.
“My team has concluded that the rupture of this elbow appears to be the initiating event causing the process fluid release,” said Lauren Grimm, a CSB investigator.
According to Grimm, an adjacent pipe elbow measured .311 inches in a 2018 inspection. She said the faulty pipe elbow’s steel composition had a relatively high concentration of nickel and copper, which are metal elements known to cause steel to corrode at a faster rate compared to steel with lesser concentrations of nickel and copper. It was installed at the facility in the 1970s.
As a result of the explosion, “about 676,000 pounds of hydrocarbons were released” and “about 608,000 pounds were combusted during the fire,” said Grimm. According to Grimm, low concentration hydrofluoric acid was also present in some of the process piping and equipment that failed during the incident, causing HF to release into the atmosphere. Grimm said that PES estimated there was about 5,239 pounds of HF, or hydrofluoric acid, released from the piping during the incident, 1,968 pounds of which were contained by water spray. As a result, the remaining 3,271 pounds were released into the atmosphere, putting the health of local communities at risk. According to the Centers for Disease Control and Prevention, HF can irritate the eyes, nose and respiratory tract even in small amounts. Breathing in hydrogen fluoride at high levels or in combination with skin contact can cause death from an irregular heartbeat or from fluid buildup in the lungs. Swallowing a small amount of highly concentrated hydrogen fluoride will affect major internal organs and may be fatal. According to the report released by the CSB, the fluid in the piping contained about 2.5% HF. Approximately 94.7% of the fluid consisted of propane, and the remaining 2.8% was made up of “additional hydrocarbons.”
Despite these facts, the CSB says it is “unaware of anyone experiencing health impacts from the hydrofluoric acid release” in a video released showing an animation of the accident (the animation can be viewed on the CSB’s YouTube channel).
The CSB has seen similar incidents regarding explosions caused by corrosion in recent years, said Grimm. Among them were the 2012 Chevron Richmond Refinery explosion in California and the 2009 Silver Eagle Refinery fire in Utah.
“One of the frustrating things about working at the CSB is seeing the same kind of incident happening over and over again,” said CSB Interim Executive Authority Kristen Kulinowski. “We are all very fortunate that there were no fatalities or serious injuries as a result of this catastrophic incident.”
After the Chevron incident, the CSB made a recommendation to inspect all components in the piping circuit and called for “100 percent component inspection in order to effectively monitor that type of corrosion,” said Kulinowski. “The CSB is concerned that the lessons from the Chevron incident were not more broadly applied across the refining industry.”
In addition, the CSB announced that during the explosion, a 38,000-pound vessel fragment was launched from the facility, landing on the opposite bank of the Schuylkill River. Two more vessel fragments – one weighing 23,000 pounds and the other about 15,500 pounds – landed inside the refinery.
“We are lucky that there were no serious injuries or fatalities from the explosion or the HF release,” said Kulinowski. “The board remains concerned that the next time there is a major explosion at a refinery that uses HF for alkylation, workers and those living nearby will not be so lucky.”
The CSB is an independent federal agency charged with investigating industrial chemical incidents. The agency’s board members are appointed by the president and confirmed by the Senate. CSB investigations analyze all aspects of chemical accidents, including physical causes such as equipment failure as well as inadequacies in regulations, industry standards and safety management systems. The Board does not issue citations or fines but does make safety recommendations to plants, industry organizations, labor groups and regulatory agencies such as OSHA and EPA.