Hydrogen-Air Explosion in an Ammonia Plant
This resulted in the destruction of the building where the explosion occurred and claimed the lives of two people. The triggering event was a blowing out of a gasket in a water pump situated in a 100 m long, 10 m wide and 7 m high building. The pump fed water to a vessel that contained hydrogen gas at 30 bars. The pressure caused a back flow of water flow through the pump and out of the failed gasket. The hydrogen reached the leakage point after approximately 3 minutes. The discharge of gas lasted 20 - 30 seconds before the explosion. The total discharge of hydrogen inside the building was about 10 - 20 kg. Most likely a hot bearing ignited the gas cloud.The main explosion was very violent and it is likely that the gas cloud detonated. 3.5 - 7 kg of hydrogen must have been burning during 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 roof of the building was lifted by an estimated 1.5 meters before resettling. The displacement of the roof caused a guillotine break of a 350 mm diameter pipe connected to the vessel that was the source of the original gas discharge. The gas composition in the vessel was 65 - 95 % hydrogen. This resulted in a large horizontal jet fire lasting about 30 seconds. Minor explosions occurred in the plant culvert system.The explosion caused large number of fragments representing a severe hazard. Glass windows were broken up to 700 m from the center of the explosion. Within a radius of 100 m all ordinary windows were broken.
Event Date
August 1, 1985
Record Quality Indicator
Region / Country
Event Initiating System
Classification of the Physical Effects
Nature of the Consequences
Causes
Cause Comments
The immediate cause was the failure of a gasket in a water pump connected to a H2 vessel. The root cause was a combination of operational error, technical failures and weakness in the design
Facility Information
Application Type
Application
Specific Application Supply Chain Stage
Components Involved
hydrogen vessel, water pump
Storage/Process Medium
Storage/Process Quantity
20
Actual Pressure
30
Design Pressure
30
Location Type
Location description
Industrial Area
Operational Condition
Pre-event Summary
The accident occurred when operators were trying to switch from one water pump to another. They did not realize that the inlet valve on the low-pressure side of first pump was closed. This resulted in a series of failed attempt to bring the situation back to normal.
Currency
Lessons Learned
Lessons Learned
The main conclusion from the investigation can be summarized as follows: The accident occurred due to a combination of operational error, technical failures and weakness in the design No recommendation is available, but the investigators also issued advices for an optimal investigation process.1.Documentation of the damage has to start immediately, and should be done by an explosion expert and a structural response expert(s). 2.Take many photographs, both of the area view and the specific damages. Use a professional photographer and make systematic records of locations and directions of all the photos taken. 3.Organize a fragment map, showing the original position of the fragments and where they landed. Fragments can be a good indicator of where the explosion occurred and of the magnitude of the explosion
Event Nature
Emergency Action
Unknown
Ignition Source
Detonation
No
Deflagration
No
High Pressure Explosion
No
High Voltage Explosion
No
Flame Type
Source Category
References
References
proceedings of the ICHS 2005
Bjerketvedt and Mjaavatten, A HYDROGEN-AIR EXPLOSION IN A PROCESS PLANT: A CASE HISTORY
available at:
http://conference.ing.unipi.it/ichs2005/Papers/100096.pdf