Safety Gaps Refinery Blast Cause: CSB

Friday, May 12, 2017 @ 02:05 PM gHale


Multiple gaps in the former ExxonMobil refinery’s process safety management system allowed for the operation of the fluid catalytic cracking (FCC) unit without pre-established safe operating limits and criteria for a shut down, according to the final report on a February 2015 explosion at the Torrance, CA, facility, federal officials said.

The U.S. Chemical Safety Board (CSB) released its final report into the February 18, 2015, blast at the ExxonMobil refinery in Torrance, California. The blast caused serious property damage to the refinery and scattered catalyst dust up to a mile away from the facility into the nearby community. The incident caused the refinery to run at limited capacity for over a year, raising gas prices in California and costing drivers in the state an estimated $2.4 billion.

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The explosion occurred in the refinery’s FCC unit, where a variety of products, mainly gasoline, are produced. A reaction between hydrocarbons and catalyst takes place in what is known as the “hydrocarbon side” of the FCC unit. The remainder of the FCC unit is comprised of a portion of the reaction process and a series of pollution control equipment that uses air and is known as the “air side” of the unit.

The CSB’s report found it is critical that hydrocarbons do not flow into the air side of the FCC unit, as this can create an explosive atmosphere. The CSB determined on the day of the incident a slide valve that acted as a barrier failed. That failure ultimately allowed hydrocarbons to flow into the air side of the FCC, where they ignited in a piece of equipment called the electrostatic precipitator, or ESP, causing an explosion of the ESP.

“This explosion and near miss should not have happened, and likely would not have happened, had a more robust process safety management system been in place,” said CSB Chairperson Vanessa Allen Sutherland. “The CSB’s report concludes that the unit was operating without proper procedures.”

In its final report, the CSB describes multiple gaps in the refinery’s process safety management system, allowing for the operation of the FCC unit without pre-established safe operating limits and criteria for a shut down. The refinery relied on safeguards that could not be verified, and re-used a previous procedure deviation without a sufficient hazard analysis of the current process conditions.

Finally, the slide valve — a safety-critical safeguard within the system — was degraded significantly. The CSB said it is vital to ensure safety critical equipment can successfully carry out its intended function. As a result, when the valve was needed during an emergency, it did not work as intended, and hydrocarbons were able to reach an ignition source.

The CSB also found in multiple instances leading up to the incident, the refinery directly violated ExxonMobil’s corporate safety standards. The CSB found during work leading up to the incident, workers violated corporate lock out tag out requirements.

In July 2016, the Torrance refinery was sold by ExxonMobil to PBF Holdings Company, LLC, which now operates as the Torrance Refining Company. Since the February 2015 explosion, the refinery has experienced multiple incidents.

“There are valuable lessons to be learned and applied at this refinery, and to all refineries in the U.S.,” Sutherland said. “Keeping our refineries operating safely is critical to the well-being of the employees and surrounding communities, as well as to the economy.”

The CSB investigation also discovered that a large piece of debris from the explosion narrowly missed hitting a tank containing tens of thousands of pounds of modified hydrofluoric acid, or MHF. Had the tank ruptured, it would have caused a release of MHF, which is highly toxic. ExxonMobil, the owner-operator of the refinery at the time of the accident, did not respond to the CSB’s requests for information detailing safeguards to prevent or mitigate a release of MHF, and therefore the agency was unable to fully explore this topic in its final report.

“Adoption of and adherence to a robust safety management process would have prevented these other incidents,” Sutherland said. “In working with inherently dangerous products, it is critical to conduct a robust risk management analysis with the intent of continual safety improvement.”



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