Details

Category: Human Factors Engineering

Published: 05 January 2020

The NTSB has determined that the probable cause of the 2018 Hydrogen tube trailer fire in California was human errors made by two non-related personnel from two different companies with both workers making errors on the pressure relief system:

1. 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
2. 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.

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