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CSB final report into 2015 California refinery blast blames gaps in ExxonMobil’s process safety management

04 May 2017

A 2015 explosion at the Torrance oil refinery in suburban Los Angeles injured four workers and threatened to release a toxic cloud endangering 150,000 nearby residents, the US Chemical Safety and Hazard Investigation Board (CSB) said in its final report on the incident issued on May 3. The 73-page report identified technical issues that led to the blast and indicated that safety issues remain on the site.

Animation of the Torrance explosion - Image: CSB
Animation of the Torrance explosion - Image: CSB

ExxonMobil — which owned the refinery at the time — said it regrets the incident and will work with the board to understand the findings and recommendations. The damage caused the refinery to be run at limited capacity for over a year, raising gas prices in California and costing drivers in the state an estimated $2.4 billion.

The blast on 18 February 2015 occurred when flammable hydrocarbons flowed into a spark-producing pollution control device called the electrostatic precipitator, which was being prepared for maintenance.

The explosion destroyed a large part of the refinery, shook the neighbouring community 20 miles southwest of Los Angeles and sent a fine white ash raining down on nearby homes and cars.

The blast tossed a 40-ton piece of equipment within feet of another unit where tens of thousands of pounds of modified hydrofluoric acid were stored in tanks. The safety board previously said that carried the potential to release a toxic cloud into the neighbourhood and cause "serious injury or death to many community members."

"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 Vanessa Allen Sutherland, chair of the CSB. “The report concludes that the unit was operating without proper procedures,” she added.

The explosion occurred in the refinery’s fluid catalytic cracking (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 emphasises that 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 that 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. 

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 notes that it is vital to ensure that 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 that in multiple instances leading up to the incident, the refinery directly violated ExxonMobil’s corporate safety standards. For instance, the CSB found that 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 which now operates as the Torrance Refining Company. Since the February 2015 explosion, the refinery has experienced multiple incidents, including:
*A November 15, 2016, fire that occurred while work was being conducted on a portion of the refinery;
*A February 1, 2017, fire that occurred in the Torrance refinery tank farm;
*A February 18, 2017, pump-related fire that occurred in the crude unit.

“The CSB’s final report concludes that the refinery must adopt a robust safety management system in order to prevent future incidents,” said Mark Wingard, a Chemical Safety Board investigator. “Events at this facility keep occurring — adoption of the CSB’s safety recommendations will minimize the chances of future incidents.”

PBF Energy said it already has begun taking action to address the Chemical Safety Board’s concerns and recommendations.

The company said it plans to complete two studies later this year that will help address all concerns and will invest more than $100 million in a maintenance turnaround at Torrance to improve the refinery’s operational reliability,”

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