The U.S. Chemical Safety Board (CSB) announced August 20 that it is proceeding with an investigation of the causes of a recent accident at the Goodyear rubber manufacturing facility in southeast Houston, in which one employee was killed and approximately seven others were injured, including several contract workers who were exposed to hazardous anhydrous ammonia.
CSB investigators have now completed two week-long visits to the plant conducting interviews and gathering other evidence.
The accident occurred on June 11 during a maintenance operation on a heat exchanger, which used pressurized, liquid ammonia to cool chemicals that are later processed to make synthetic rubber. The rubber-making chemicals were pumped through steel tubes inside the heat exchanger, while ammonia flowed through a cylindrical steel shell that surrounded the tubes.
The day prior to the accident, the process was shut down for cleaning. During the shutdown, an isolation valve was closed between the heat exchanger and a pressure-relief device designed to protect the heat exchanger from possible over-pressure. On the morning of the accident, an operator used steam to clean out process piping; the steam also flowed through the heat exchanger tubes. The steam heated the liquid ammonia remaining in the exchanger shell which caused the pressure to build. With the path to the pressure-relief device blocked, the heat exchanger ruptured catastrophically.
An operations supervisor, who was not involved in the maintenance work but was working in the area, was killed by the explosion. Her body, which was covered with explosion debris, was not discovered until several hours after the emergency had been declared over.
"This tragic accident is but the latest example of the destruction that can result from a lack of effective pressure relief systems and practices," said CSB Chairman John Bresland, who personally visited the accident site on June 12. "Companies should be vigilant to ensure that pressure-relief systems are adequate and are properly maintained and operated to continuously protect equipment from over-pressure."
Chairman Bresland said the CSB investigation would likely focus on the company's practices for managing, inspecting, and maintaining relief systems; training operators; and accounting for workers during emergencies. A case study report is expected at the end of 2008.
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 regulations, industry standards, and 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. To learn more, visit www.csb.gov.