National Transportation Safety Board issues 6 Safety Recommendations Following Investigation of Hydrogen Release, Fire | site |

(November 19, 2019) - - Today (November 19, 2019), the National Transportation Safety Board (NTSB) published the following information:

The National Transportation Safety Board issued Hazardous Materials Incident Report 19/02, Tuesday, following its investigation of the Feb. 11, 2018, release of compressed hydrogen and subsequent fire in Diamond Bar, California.

No injuries were reported in connection with the incident but approximately 1,500 people were evacuated and resulting damages were estimated at $175,000.

An Air Products tube trailer with a mounted Structural Composite Industries model CT-250 tube trailer module with 25 cylinders, 24 of which were fully loaded with compressed hydrogen, caught fire while being transported on Golden Springs Drive, Diamond Bar. The incident happened when an incorrect pressure relief device in a cylinder actuated. The force of the high-pressure hydrogen releasing from the cylinder caused the pressure relief device vent tubing to eject from its fitting and allowed a hydrogen field fire to develop inside the module. Hydrogen is a colorless and odorless Division 2.1 flammable gas that must be compressed and transported at high pressure for commercially useful quantities. Hydrogen is extremely flammable, may form explosive mixtures in air, burns with an invisible flame and may ignite if a cylinder valve is opened to the air.

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(The post-incident, rear view of Air Products module number 430003 is seen in this image taken March 12, 2018. The area of greatest thermal damage is circled in red. NTSB photo illustration by Paul Stancil)

NTSB investigators determined that while the trailer module gas cylinders were subjected to a required 5-year requalification inspection and pressure test, the testing facility technicians installed four incorrect pressure relief devices that were designed to activate at almost one-half the required operating pressure of 10,000 pounds per square inch. The incorrect devices were inadvertently commingled in the facility’s inventory and went unnoticed by the inspector. NTSB also found pressure relief device vent tubing attached by compression fittings to seven of the module’s cylinders were not sufficiently secured when manufactured and technicians did not inspect the fittings for securement.

The NTSB initiated its investigation of the incident to evaluate the safety of mobile hydrogen tube trailer modules used as fueling stations for hydrogen fuel cell electric vehicles. As of April 25, 2018, the California Fuel Cell Partnership reported the state had 36 open retail and non-retail hydrogen fueling stations with 28 more in various stages of planning and construction.

Based on the findings of its investigation the NTSB issued six safety recommendations with four issued to the Pipeline and Hazardous Materials Safety Administration and one each to the Department of Energy’s Pacific Northwest National Laboratory and the Compressed Gas Association. The recommendations address the need for information and guidance on managing incidents involving fuel cell electric vehicles and hydrogen fueling infrastructure, a requirement for requalification inspections to include correct pressure relief devices are used and testing of device venting equipment, the development of design guidelines for tube trailer pressure relief vent systems, emergency responder training for hazard recognition and firefighting involving tube trailers and fuel cell electric vehicle fueling infrastructure and guidelines for tube trailer pressure relief device vent systems.

Hazardous Materials Incident Report 19/02 is available online at .

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