Hydrogen Release from a Desulfurization Unit in a Refinery
The charge pump on a hydro-desulfuriser unit tripped. The charge flow control valve then opened wide on low flow. The high pressure hydrogen supply to the unit flowed backwards through a faulty non-return valve to the charge tank.The tank vents were not designed for this high flow of gas and so the weak roof to the wall seam failed. Fortunately, the gas did not find a source of ignition and so there was no fire. The pump could have failed due to reverse rotation, but did not.
Event Date
January 1, 1976
Record Quality Indicator
Region / Country
Event Initiating System
Classification of the Physical Effects
Nature of the Consequences
Causes
Cause Comments
The immediate cause was a mechanical equipment failureThe root cause could be perhaps found in design or operation cause (failure of proper maintenance or inspection). The safety design did not take into account this type of event sequence.
Facility Information
Application Type
Application
Specific Application Supply Chain Stage
Components Involved
desulfurization unit, control valve, pump tank
Storage/Process Medium
Location Type
Location description
Industrial Area
Lessons Learned
Lessons Learned
According to the ICHEME database, the following measures were requested: 1. To identify all critical non-return valves which could cause a serious incident when failing. These valve have to be repaired to as new condition at scheduled shutdowns. 2. To identify the case where reverse flow should not be relied on as the sole means of preventing a serious incident. In those cases, to modify operations in such a way that the flow control valve close any time that the pump tripped.
Event Nature
Emergency Action
Unknown
Release Type
Release Substance
Hydrogen Release Concentration (%)
100.00
Detonation
No
Deflagration
No
High Pressure Explosion
No
High Voltage Explosion
No
Source Category
References
References
Event description at the UK database ICHEME
https://www.icheme.org/knowledge/safety-centre/resources/accident-data/
(accessed September 2020)