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Image courtesy of the US Chemical Safety Board.

In a report published last Friday, the US Chemical Safety Board (CSB) said that loose pipe fittings caused the 84,000 pound sulfuric acid spill that seriously injured two workers at Tesoro’s Golden Eagle refinery on February 12.

Golden Eagle is located in Martinez, California, about 35 mile northwest of San Francisco.

The report was prepared by California engineering and laboratory testing firm Anamet Inc.

The report details findings from an examination of a stainless-steel tube assembly recovered from the accident site by the California Division of Occupational Safety and Health (Cal/OSHA).

The report said that the tubes and a compression joint at the sulfuric acid sampling station were not sufficiently tightened during installation.

The tubes were shaken loose from the compression joint when they were pressurized.

Cal/OSHA closed down the Golden Eagle alkylation unit from February 18 to 28.

Employees told Cal/OSHA that they had been afraid to work in the unit before the accident because of safety concerns.

“This incident highlights the need for strong process safety management at facilities that ensures mechanical integrity is verified prior to the introduction of hazardous chemicals into equipment,” CSB Chairperson Rafael Moure-Eraso said.

Moure-Eraso said the need for safety management is pressing because of another sulfuric acid spill at the same refinery on March 10.

Two contract workers were sprayed with sulfuric acid while conducting planned maintenance during that incident.

“Four workers burned by sulfuric acid in less than a month clearly demonstrates there are significant opportunities within the refinery for improvement in safety performance,” Moure-Eraso said.

Cal/OSHA is continuing a separate investigation at the refinery, focusing on the refinery’s mechanical integrity and operating procedures.

The Golden Eagle refinery has a crude oil capacity of 166,000 barrels per day and employees 650 people.

San-Antonio based Tesoro is an independent downstream company.

Tesero has not commented on the report.