In a report adopted today, the National Transportation Safety Board determined that inadequate securement and protection of cylinders, valves and piping carrying flammable hydrogen gas contributed to the severity of a truck accident near Ramona, Oklahoma in May 2001.
On May 1, 2001, a tractor semi-trailer carrying horizontally mounted cylinders filled with compressed hydrogen gas struck a pick-up truck on U.S. Highway 75 just south of Ramona, Oklahoma. During the crash some of the cylinders, valves, piping and fittings at the rear of the semi-trailer were damaged and released the hydrogen gas. The hydrogen ignited, burned the rear of the semitrailer and caused 5 area homes to be evacuated. The driver of the tractor-trailer died in the accident.
While the Board cited the pick-up truck driver's failure to control her vehicle as the probable cause for the accident, the report also examined federal requirements for protecting horizontally mounted cylinders and their valves and fittings in rollover accidents as well as the accuracy of information about compressed hydrogen provided in the North American Emergency Response Guidebook.
Through the investigation the Board determined that the valves, piping and fittings at the rear of the semitrailer were not adequately protected for a rollover impact. Eight of 10 shutoff valves were sheared off, causing the release and ignition of the hydrogen. Because the outermost cylinders typically extend beyond the top and side edges of the trailer bulkheads they are vulnerable to initial impact with roadway or terrain creating an increased risk of damage, failure and ejection in an accident.
The report also noted that the North American Emergency Response Guidebook, used by first responders to determine the appropriate response to a hazardous materials incident, contains incomplete and inaccurate information on compressed hydrogen. Although the lack of correct information did not escalate the crisis in Ramona, the Board is concerned that the deficiency could place first responders at risk in future accidents.
As a result of the investigation the Board recommended that the Research and Special Programs Administration (RSPA) modify regulations for the protection of valves, piping and fittings on horizontally mounted cylinders; require horizontal cylinders be protected from impact with the roadway or terrain; and revise the North American Emergency Response Guidebook to include information about the specific chemical and flammability properties of hydrogen.
A synopsis of the report, including the findings, probable cause, and safety recommendations can be found on the Board's web site at www.ntsb.gov. The complete report will be available in about one month.