On February 11, 2018, at approximately 1:15 p.m. PST, a release of compressed hydrogen occurred from a tube trailer module operated by Air Products and Chemicals, Inc. The incident took place on Golden Springs Drive in Diamond Bar, California. The tube trailer module, mounted on a 2015 Cheetah Chassis Corporation chassis and towed by a 2014 Mack CXU613 truck tractor, contained 25 fully wrapped carbon fiber-reinforced aluminum-lined cylinders, with 24 of them fully loaded with approximately 240 kilograms of compressed hydrogen. The release led to a subsequent fire, activating pressure relief devices on 12 cylinders, releasing about 120 kilograms of hydrogen, which was likely consumed in the fire. The Los Angeles County Fire Department evacuated an estimated 1,400 to 2,000 people from the adjacent business district and nearby residential area. Equipment damages were estimated at $175,000.
Date
Location
Industry
Substance
Cause
The probable cause was the installation of an incorrectly rated pressure relief device in cylinder No. 14 by a requalification technician, which actuated during normal transportation and released high-pressure hydrogen.
Contributing factors included:
• The tube trailer module assembly contractor’s failure to sufficiently tighten compression fittings on the pressure relief device vent lines. These disassembled under the pressure of escaping gas, allowing a fire to develop inside the module and impinge on adjacent cylinders.
• Lack of a requirement for requalification inspectors to verify the pressure relief device pressure rating and to inspect for vent line assembly securement.
Consequence
- Activation of PRDs on 12 cylinders, releasing approximately 120 kilograms of hydrogen.
- Subsequent fire consuming the released hydrogen.
- Evacuation of approximately 1,400 to 2,000 individuals from nearby areas.
- Equipment damages estimated at $175,000.
- No reported injuries or fatalities.
Injuries
None reported.
Fatalities
None reported.
Lessons Learned
- Emergency responder awareness is critical; training is needed for incidents involving hydrogen tube trailer modules.
- Requalification and inspection requirements must be improved to prevent similar incidents. This includes verifying PRD compatibility and vent line securement.
- Hydrogen tube trailer component design criteria need to be enhanced, particularly for PRD vent systems.
- The importance of verifying that PRDs of the correct pressure rating are used.
- The importance of ensuring that PRD venting equipment is inspected and tested.
Analysis
The incident in Diamond Bar, California, on February 11, 2018, was initiated by the installation of an incorrectly rated pressure relief device (PRD) in cylinder No. 14. This PRD, designed to activate at 5,833 psi, was mistakenly installed instead of the required 10,000 psi PRD during a requalification inspection. During normal transportation, the incorrect PRD actuated, releasing high-pressure hydrogen. The force of the escaping gas caused the pressure relief device vent tubing to eject from its fitting because the compression fittings were not sufficiently tightened. This directed the hydrogen into the interior of the module, leading to a fire that damaged 21 of the cylinders.
The fire’s intensity caused six additional pressure relief device vent tubes to eject from improperly secured compression fittings, further escalating the situation
The Los Angeles County Fire Department (LACoFD) responders lacked familiarity with hydrogen tube trailer modules, which added to the initial confusion and challenges in managing the incident. The generic guidance in the Emergency Response Guidebook (ERG) Guide 115 did not adequately address the unique hazards associated with compressed hydrogen, further complicating the emergency response.
As a result of the incident, several safety recommendations were made to prevent similar occurrences in the future:
• The Pipeline and Hazardous Materials Safety Administration (PHMSA) was urged to revise the Emergency Response Guidebook (ERG) to include specific information about hazards and protective actions for hydrogen, as well as guidance for managing incidents involving fuel cell electric vehicles (FCEVs) and hydrogen fuelling infrastructure.
• PHMSA was also recommended to revise hazardous materials special permits for transporting gases in manifolded horizontal cylinders. The revision would require that requalification inspections include verifying that PRDs of the correct pressure rating are used and that PRD venting equipment is inspected to ensure it can withstand forces generated by PRD actuation.
• Additionally, PHMSA was advised to revise Title 49 Code of Federal Regulations Part 180, subpart C, “Requirements for Requalification of Specification Cylinders,” to ensure that inspectors verify PRD pressure ratings and inspect venting equipment.
• PHMSA was encouraged to collaborate with the Compressed Gas Association (CGA) to develop design guidelines for tube trailer PRD vent systems.
• The US Department of Energy, Pacific Northwest National Laboratory, was recommended to revise its hydrogen emergency responder training programs to include specific information and guidance on hazard recognition and firefighting related to tube trailers and FCEV fuelling infrastructure.
• The Compressed Gas Association (CGA) was also advised to work with PHMSA to develop design guidelines for tube trailer PRD vent systems.
These recommendations emphasise the need for improved training, stricter inspection protocols, and better design standards to enhance the safety of hydrogen transportation.