A ruptured section of metal piping installed more than 40 years ago led to an uncontrolled release of hazardous materials at the Philadelphia Energy Solutions Refining and Marketing Refinery (PES) in Philadelphia, Penn., on June 21, causing a fire and three explosions, according to a U.S. Chemical Safety and Hazard Investigation Board (CSB) report. The incident occurred in the PES Girard Point refinery hydrofluoric acid alkylation unit.
A ruptured pipe elbow found in the unit after the fire and explosions appeared to be what initiated the process fluid release, according to the report. The piping circuit containing the ruptured elbow seemed to be the original piping installed in approximately 1973.
At about 4 a.m. on June 21, flammable process fluid containing hydrofluoric acid released from the PES alkylation unit, forming a vapor cloud which then ignited and caused a large fire in the unit.
Three explosions followed, the largest occurring when the V-1 Treater Feed Surge Drum containing primarily butylene, isobutane and butane, ruptured. This explosion launched an approximately 38,000-pound fragment of the drum across the Schuylkill River, and two other fragments – one weighing about 23,000 pounds and the other weighing about 15,500 pounds – landed in the PES refinery.
The CSB report said that PES estimates about 676,000 pounds of hydrocarbons released during the event, of which an estimated 608,000 pounds were combusted. Low-concentration hydrofluoric acid was also present in some of the process piping and equipment that failed during the incident, causing hydrofluoric acid to release to the atmosphere, the report added.
Hydrofluoric acid is a highly toxic chemical. PES estimates that 5,239 pounds were released from piping and equipment during the incident. It also estimates 1,968 pounds of the released hydrofluoric acid was contained by water spray within the unit and was processed in the refinery wastewater treatment plant, while 3,271 pounds was released to the atmosphere and was not contained by water spray.
The fire was extinguished the following day, Saturday, June 22, at about 8:30 a.m, according to the report. While five workers experienced minor injuries during the incident and response, requiring first aid treatment, The U.S. Chemical Safety and Hazard Investigation Board said in its report it is unaware of any offsite or onsite health impacts from the hydrofluoric acid release.
On June 26, PES announced the refining complex would be shutting down, and on July 22, PES filed for bankruptcy.
About 1,100 workers of the plant were laid off without health benefits or severance pay, according to a Reuters report.
“We need to focus on making sure that this type of an explosion at a refinery doesn’t happen anymore because it’s just a matter of time before the facts are just a little bit different and people die or are critically injured,” CSB Interim Director Kristen Kulinowski said at a news conference, as reported by Reuters.
The investigation into the incident is ongoing. CSB will publish a final investigation report discussing findings, analysis and issuing recommendations after the investigation is complete, the report said.
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