In April 2010, a 40-year-old heat exchanger at the Tesoro Refinery in Anacortes, Washington, failed catastrophically. The incident resulted in an explosion and fire that killed seven workers. The U.S. Chemical Safety Board’s (CSB) investigation of the incident, completed in 2014, found that the failure was caused by damage to the heat exchanger, a mechanism known as “high temperature hydrogen attack,” (HTHA), which severely cracked and weakened carbon steel tubing and lead to a rupture. The CSB faulted Tesoro’s preventive maintenance practices for failing to identify the damage.
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As a result of the Tesoro investigation and other investigations, the CSB has announced that “preventive maintenance” is one of its “most wanted safety improvements.”
Timely Inspections and Maintenance Scheduling
Whenever the CSB conducts an investigation, it makes recommendations aimed at addressing problems that contributed to the disaster. At the present time, the CSB has 21 “open” recommendations (recommendations that have not been addressed) arising out of 11 investigations. These are aimed at addressing gaps at the level of individual facilities, corporate policies, regulatory programs, and industry standards.
The CSB has identified preventive maintenance issues at chemical facilities as recurring root causes in the incidents it investigates. These problems could be solved at the facility level. The CSB recommends that chemical facilities:
- Promptly identify equipment upgrades.
- Ensure that replacements are not delayed.
- Ensure that equipment is not made to operate longer than it should.
In particular, the CSB has identified persistent problems in refineries and chemical facilities with:
- Inadequate mechanical integrity programs. In 2012, a catastrophic pipe failure led to massive fire at the Chevron Refinery in Richmond, California. The incident released toxic smoke that sent 15,000 nearby residents to the hospital with respiratory symptoms. Testing determined that a pipe failed due to thinning caused by sulfidation corrosion, a common damage mechanism in refineries. The CSB found that Chevron’s mechanical integrity program had failed to identify and evaluate damage mechanism hazards which, if acted on, would likely have identified the possibility of a catastrophic sulfidation corrosion-related piping failure.
- Delayed or deferred preventive maintenance. Are you conducting inspections on the schedule recommended by the equipment manufacturer or by your trade group? A lack of timely inspections that can lead to delayed or deferred preventive maintenance has been a persistent problem for chemical facilities that experience disastrous equipment failures. The CSB recommends that facilities institute comprehensive preventive maintenance schedules for all process equipment.
- Aging infrastructure. When preventive maintenance is delayed or deferred, infrastructure ages to the point that it begins to fail. At the Chevron refinery, the CSB found that Chevron repeatedly failed over a 10-year period to upgrade the corroded piping in its crude oil processing unit, leading to the rupture.
Tomorrow, we’ll look at CSB’s other “most wanted” safety improvement: emergency planning and response.