NTSB calls for new rules governing hazmat loading, unloading
Jul 8, 2002 12:00 PM
The National Transportation Safety Board (NTSB) has called on the Department of Transportation (DOT) to develop additional safety requirements governing the loading and unloading of highway cargo tanks, railroad tank cars, and other bulk containers. The recommendation follows the board's investigation into a July 14, 2001, hazardous materials release and subsequent fire that killed three employees at an ATOFINA Chemical Co plant in Riverview, MI.
"By its very nature, the work these employees performed around chemicals was extremely hazardous," says NTSB Chairman Marion Blakey. "The lack of some basic safety precautions in this operation was a fundamental flaw, and proved tragic for the three men who lost their lives last July."
The accident occurred when a pipe attached to a fitting on the unloading line of a railroad tank car fractured and separated, causing the release of methyl mercaptan, a poisonous and flammable gas. About 25 minutes later, the methyl mercaptan ignited, engulfing the tank car in flames and sending a fireball approximately 200 feet into the air. About 2,000 residents were evacuated from their homes for about 10 hours, according to the NTSB.
The board found that current federal oversight of loading/unloading operations is deficient. It pointed out that rules governing railroads do not address the inspection, maintenance, and support of cargo transfer fittings, leak test procedures for fittings, or the use of personal protection equipment by operators. As a result, the NTSB recommended that DOT, with the assistance of the Environmental Protection Agency and the Occupational Safety and Health Administration, promulgate new rules to address these deficiencies. In addition, NTSB recommended that the Federal Railroad Administration warn companies involved in tank car loading and unloading operations that tank car excess flow valves cannot be relied upon to stop leaks that occur during those operations.
After the incident, NTSB determined that the probable cause was a fractured cargo transfer pipe that resulted from the failure of ATOFINA to adequately inspect and maintain its cargo transfer equipment and inadequate federal oversight of unloading operations involving hazardous materials. Contributing to the accident was ATOFINA’s reliance on a tank car excess flow valve to close off leaks (the device was not appropriate for this type of leak) and the company’s failure to require employees to wear appropriate safety equipment. The workmen were not wearing self-contained breathing apparatus (SCBA) and were in fact instructed to detect by odor the release of methyl mercaptan. In addition, the only way to shut off the flowing product in the event of a leak like this was to use a manual valve on top of the tank car. No remote cutoff switch was installed, according to NTSB.
The pipe that failed had been weakened by erosion and corrosion that occurred over a protracted period of time. Visual inspections failed to detect the deteriorating condition of the pipe. Since the accident, ATOFINA has made a number of changes to its plant procedures and equipment to address problems identified during this investigation. The company now requires that the cargo unloading apparatus, including the integral piping, be removed from service every two years and undergo non-destructive testing to ensure that it is still safe. Additionally, ATOFINA has redesigned the unloading apparatus. Operators are now required to wear SCBAs when working on the methyl mercaptan tank cars, and they are required to carry an escape hood with an emergency air supply when in the area of the tank cars. In addition, operators now perform leak tests on the unloading apparatus before opening the valve to the tank car, according to the NTSB.