Liquid Hydrogen Tank Explosion
A 9000 gal (34 m3) LH2 storage tank exploded during repair of the vent stack. Few days before the explosion, the tank had been filled with LH2, but later on the hydrogen released and ignited at the tank pressure control system, damaging the vent stack. To perform the required repairs, the tank had to be emptied. To this purpose the vessel was purged with nitrogen gas to display the LH2 by letting it boiling. However, the pressure inside the vacuum jacket increased because of the opening the vacuum valve. This pressure increase eventually led to the catastrophic tank rupture. One end of the tank blew off. Nobody was hurt, but the pressure wave caused significant property damage. The detailed events sequence was: Thursday : Tank filled with 9000 gal LH2.Friday : Pressure in the vacuum jacket was 30 microns (0.03 Tor = 40 10-6 bar).Saturday, 12:05 p.m. Fire erupted on the controls end of the tank. The fire folded the vent stack over and it was finally cut off just below the fold. The tank needed repair.Saturday, 7:30 p.m. : Nitrogen gas was injected into the tank to boil away the LH2.Sunday, 9:00 a.m. The nitrogen purge was stopped since it was too slow. The pressure in the vacuum jacket was 300-350 microns. The valve to the vacuum jacket was slightly opened.Sunday, 10:30 p.m. : The pressure in the vacuum jacket had risen to about 850 microns (0.85 Tor = 1 10-3 bar).Sunday,11:30 a.m. The vacuum valve was opened completely and water was sprayed onto the tank to prevent a subsequent fire.Sunday, 12:05 p.m.: The tank exploded.
Event Date
January 1, 1985
Record Quality Indicator
Event Initiating System
Classification of the Physical Effects
Nature of the Consequences
Causes
Cause Comments
According to the references, the calculations show clearly that the incident was initiated by the opening of the vacuum valve, which resulted in the establishment of a good thermal exchange between the internal vessel and the external jacket. The various references do not explain the reason for the opening of the vacuum valve. Considering the need to empty the tank, it can be assumed that this was a measure to allow for a quicker boil-off. In this sense, the root cause could be attributed to a human (assessment) error and/or to management shortcoming, due to the absence of a procedure based on risk assessment.
Facility Information
Application Type
Application
Specific Application Supply Chain Stage
Components Involved
storage tank
Storage/Process Medium
Storage/Process Quantity
2400
Storage/Process Units
Actual Pressure
30
Location Type
Location description
Unknown
Operational Condition
Pre-event Summary
TANK CHARACTERISTICSThe vacuum jacket was filled with Peaxlite insulation. The outer tank was 9 ft in diameter and 38 ft long. The inner tank was 6 ft 10 in. in diameter and 35 ft long. The tank was mounted horizontally on two concrete footings. The aluminum tank was an alloy of type SB-209-5083-0 having a wall thickness of 0.693 in. and a tensile strength of 40,000-51,000 psi. The steel tank, which was type SA-36, had a wall thickness of 5//16 in. and a tensile strength of 36,000 psi.
Lessons Learned
Lessons Learned
In absence of effective pressure release measures, and under accidental increased heat exchange, the LH2 boil-off can cause the tank internal pressure to reach values well beyond those allowed by the structural integrity of the tank.
Event Nature
Emergency Action
One of the source reprots that water was spayed on the tank during the emptying operation. It is unclear why.
Detonation
No
Deflagration
No
High Pressure Explosion
No
High Voltage Explosion
No
Source Category
References
References
M.A.K. Lodhi, R.W. Mires, How safe is the storage of liquid hydrogen?, Energy 14 (1989) 35-43
https://doi.org/10.1016/0360-3199(89)90154-7
Mires, Analysis of liquid hydrogen explosion, The Physics Teacher 23, 533–535 (1985)
https://doi.org/10.1119/1.2341906
Verfondern, Safety Considerations on Liquid Hydrogen, Jülich, Volume 10 (2008) ISBN 978-3-89336-530-2