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This data is from the European Hydrogen Incidents and Accidents database HIAD 2.1, European Commission, Joint Research Centre.

Explosion on a Water Pump Due to Hydrogen Backflow
The event started when a gasket in a water pump was blown out. The water pump was situated inside a 100 m long, 10 m wide, and 7 m high building. The pump was feeding water to a vessel containing hydrogen gas at pressure of 30 bars. The accident occurred when operators tried to change over from pump B to pump A. They did not realise that the inlet valve on the low-pressure side of pump A was closed. Following a series of attempt to solve the situation, a valve remained partially open and the gasket failed. This pressure caused a back flow of water flow through the pump and out through the failed gasket. The hydrogen reached the leakage point after about 3 minutes. The discharge of gas lasted some 20 to 30 seconds before the explosion occurred. The total mass of the hydrogen discharge was estimated at 10 to 20 kg hydrogen. The ignition source was almost certainly a hot bearing. 3.5 to 7 kg of hydrogen are estimated to have burned violently in the explosion. The explosion was very violent and it is likely that the gas cloud detonated. The pressures inside the building must have reached at least the order of 10 bars. 60 meters of the sidewalls were blown out and the roof was lifted up more than one meter. As the roof lifted, it tore off a 350 mm diameter pipe coming from the wash tower. This new release resulted in a jet fire with an initial flame length of 50 meters lasting for approximately 30 sec.
Event Date
July 6, 1985
Record Quality Indicator
Region / Country
Event Initiating System
Classification of the Physical Effects
Nature of the Consequences
Cause Comments
The accident occurred due to a combination of operational error, technical failures and weakness in the design: Initiating operational event: operator's wrong procedureInitiating technical event: overheating pump and failure of a gasket.
Facility Information
Application Type
Application
Specific Application Supply Chain Stage
Components Involved
water pump, hydrogen tank
Storage/Process Medium
Actual Pressure
30
Location Type
Location description
Industrial Area
Pre-event Summary
The gas feed to the absorption tower was typically 65% hydrogen, at the outlet 95%, the rest CO2 and CO.The accident occurred when operators tried to change over from pump B to pump A. They did not realize that the inlet valve on the low-pressure side of pump A was closed.
Environmental Damage
0
Property Loss (onsite)
Y
Property Loss (offsite)
N
Lessons Learned
Lessons Learned
This gas explosion is one of the largest industrial hydrogen explosions reported till the date.The accident occurred due to a combination of operational error, technical failures and weakness in the design. 1.The explosion caused large number of fragments representing a severe hazard 2.Glass windows were broken up to 700 m from the centre of the explosion. Within a radius of 100 m all ordinary windows were broken. 3.The window fragments represent a severe hazard to humans 4.The explosion was followed by jet fire. Domino events such as fires are common after gas explosion.The investigators draw these conclusion regarding the analytical methodology:a.Documentation of the damage has to start immediately, b.Explosion expert and a structural response experts must be involved. c.Take many photographs, both of the area view and the specific damages. d.Use a professional photographer and make systematic records of locations and directions of all the photos taken. e.Organise a 10 fragment map, showing the original position of the fragments and where they landed. f.Fragments can be a good indicator of where the explosion occurred and of the magnitude of the explosiong.Damage indicators can be of great help in investigating accidental explosion.
Event Nature
Emergency Action
Unknown
Emergency Evaluation
3.5 to 7 kg of hydrogen estimated to have burned violently in the explosion. No quantitative evidence that the cloud detonated, but from the damage observed, experience from other accidents and experiments detonation seems most likely. The explosion was followed by a large horizontal jet fire lasting about 30 seconds..
Release Type
Release Substance
Hydrogen Release Concentration (%)
95.00
Release Amount (kg)
15.00
Release Pressure (bar)
30.00
Ignition Source
Detonation
No
Deflagration
No
High Pressure Explosion
No
High Voltage Explosion
No
Flame Type
Source Category
References
References

Bjerketvedt, D and Mjaavatten, A
A HYDROGEN-AIR EXPLOSION IN A PROCESS PLANT: A CASE HISTORY
First International Conference Hydrogen safety, ICHS 2005, Pisa
Paper nr. 100096

Available at (accessed May 2020):
http://conference.ing.unipi.it/ichs2005/Papers/100096.pdf

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