Near miss due to inadequate purge procedure

Event

Event ID: 391
Quality: 2
Description: During a welding operation on a LH2 fill line it was discovered that LH2 was still in the tank although it should have been drained. Hence the potential for a major explosion existed.

[Ordin, NASA (1974)]
Event Initiating system: Hydrogen System Initiating Event
Classification of the physical effects: No Hydrogen Release
Nature of the consequences: Near Miss
Macro-region: North America
Country: United States
Date: 01/01/1950 - 31/12/1974
Main component involved?: Pipe
How was it involved?: Risk Of A Flammable H2-Air Mixture
Initiating cause: Inadequate Or No Purge
Root causes: Job Factors
Root CAUSE analysis: A deviation from procedures had occurred when purging was continued without power to the tank sensing probes in the LH2 tank at the after 400th cycle. Because of the undetected presence of LH2 in the tank, when gaseous nitrogen was introduced, it liquefied and blocked the system.

Application: Non-Road Vehicles
Sub-application: Aerospace
Hydrogen supply chain stage: Hydrogen Storage (No additional details provided)
All components affected: LH2 pipe
Location type: Unknown
Location description: Industrial Area
Operational condition: Maintenance

Reference & weblink: Mishap no 50 in <br />
P. L. Ordin, Review of hydrogen accidents and incidents in NASA operations, 1974, NASA TM X-71565<br />
https://ntrs.nasa.gov/citations/19740020344
Lowesmith et al., Safety issues of the liquefaction, storage and transportation of liquid hydrogen: An analysis of incidents and HAZIDS, Int. J. Hydrogen energy (2014) https://doi.org/10.1016/j.ijhydene.2014.08.002
Hankinson and Lowesmith, Qualitative Risk Assessment of Hydrogen Liquefaction, Storage and Transportation, FCH JU project IDEALHY, Deliverable 3.10 (2013)<br />
confidential<br />
(accessed October 2025)