Albuquerque, NM, October 26, 2005 - The U.S. Chemical Safety and Hazard Investigation Board (CSB) today issued a final Case Study report examining the causes of the April 8, 2004, refinery explosions and fire that seriously injured six employees and caused an evacuation at the Giant Industries' Ciniza oil refinery in Jamestown, New Mexico, east of Gallup.
The incident occurred in the refinery's hydrofluoric acid (HF) alkylation unit. Alkylation is a standard oil refinery process that combines olefins with isobutane using a catalyst, HF in this case, to produce alkylate. Alkylate, which is highly flammable, is used to boost the octane rating of gasoline.
The CSB investigation found that the day before the incident, alkylation unit operators performed a regularly scheduled switch of the alkylate recirculation pumps in the iso-stripper section of the akylation unit. When operators attempted to put the spare pump in service, they discovered that it had a leaking mechanical seal and that it would not rotate.
The spare pump was scheduled for maintenance the next day. To isolate the pump for work, plant personnel, using a valve wrench, turned a shut-off valve connecting the pump to a distillation column to what they believed was the "closed" position. CSB investigators determined that the valve was actually open.
An operator disconnected the pump's vent hose to verify that no pressure was in the pump, and witnessed some alkylate flow through the hose. After the flow subsided, he believed the pump had been de-pressurized and was ready for removal. The study concluded that the vent line was plugged, not de-pressurized. As the mechanics were removing the pump alkylate was suddenly released at high pressure and temperature, producing a loud roar that was audible throughout the refinery. One of the mechanics was blown over an adjacent pump and broke his ribs. About 30 to 45 seconds after the initial release, the first of several explosions occurred. The plant operator was covered in alkylate that quickly ignited and seriously burned him. Other personnel suffered burns and eye injuries.
CSB lead investigator Johnnie A. Banks described several findings related to this explosion: "Giant's mechanical integrity program did not effectively prevent repeated pump seal failures. Problems were addressed when equipment broke down, not in a preventive manner. The design of the valve wrench made it easy to remove and reposition onto the valve stem in different directions, and this led to a potential hazard because operators sometimes determined whether the valve was open by its wrench position, rather than the valve position indicator. In this incident, the valve wrench collar had been installed in the wrong position. Operators depended on the wrench position and mistakenly determined the valve was closed."
The study also found that the valve had been modified in the past to replace a hand wheel method of opening and closing it with a bar-type hand wrench. If the company had performed a management of change analysis before modifying the valve, they could have recognized the hazard of identifying the valve position that this modification caused. In addition, Giant operators did not effectively verify that the pump involved in this incident had been isolated and depressurized before beginning to remove it.
Under Lessons Learned, the CSB urges management of change analyses for any valve modifications; effective "lock out tag out" programs to ensure equipment has been isolated, depressurized, and drained; and proper mechanical integrity programs to prevent breakdown maintenance. The study said Giant should have determined the cause of the frequent alkylate recirculation pump malfunctions and implemented a program to prevent them.
CSB Board Member John Bresland said, "Proper mechanical integrity programs and effective management of change analyses are essential components of safe operations at any refinery. The Board plans to disseminate this Case Study to other refineries and trade organizations to help make incidents like the one at Giant less likely to occur in the future."
The CSB is an independent federal agency charged with investigating industrial chemical accidents. The agency's board members are appointed by the President and confirmed by the Senate. CSB investigations look into all aspects of chemical accidents, including physical causes such as equipment failure as well as inadequacies in safety management systems.
The Board does not issue citations or fines but does make safety recommendations to plants, industry organizations, labor groups, and regulatory agencies such as OSHA and EPA. Please visit our website, www.CSB.gov. For more information, contact Kara Wenzel at 202-577-8448 (cell).