On February 11, 2018, at 1:15 p.m. Pacific standard time, a release of compressed hydrogen and subsequent fire occurred during the transportation of an Air Products and Chemicals, Inc. 2014 Mack CXU613 truck tractor in combination with a 2015 Cheetah Chassis Corporation chassis, with a mounted CT-250 tube trailer module. The tube trailer module contained 25 non-US Department of Transportation specification fully wrapped carbon fiber reinforced aluminum-lined cylinders, 24 of which were fully loaded with 240 kilograms of compressed hydrogen. The module caught fire on Golden Springs Drive in Diamond Bar, California. Pressure relief devices, which actuated on 12 of the cylinders, released about 120 kilograms of hydrogen that was likely consumed in the fire. The Los Angeles County Fire Department estimated about 1,400 to 2,000 people were evacuated from the adjacent business district and a nearby residential area. Equipment damages were estimated at $175,000.
We determined that the probable cause of the February 11, 2018, tube trailer module fire in Diamond Bar, California, was the requalification technician’s installation of an incorrectly rated pressure relief device in cylinder No. 14, which actuated during normal transportation and released high-pressure hydrogen, and the tube trailer module assembly contractor’s failure to sufficiently tighten compression fittings on the pressure relief device vent lines that disassembled under the pressure of escaping gas allowing a fire to develop inside the module and impinge on adjacent cylinders. Contributing to the incident was a lack of a requirement for requalification inspectors to verify the pressure relief device pressure rating and to inspect for vent line assembly securement.
We made recommendations to the Pipeline and Hazardous Materials Safety Administration, the US Department of Energy, Pacific Northwest National Laboratory, and the Compressed Gas Association.
