Event
- Event ID
- 770
- Quality
- Description
Approximately one hour into the shutdown process, a small leak of hydrogen, hydrogen sulphide, and lubricating oil was observed from the flange area of the reactor‑outlet heat‑exchanger.
- Event Initiating system
- Classification of the physical effects
- Hydrogen Release and Ignition
- Nature of the consequences
- Macro-region
- North America
- Country
- United States
- Date
- Component involved
- piping (weld)
- Failure mode
- leak & ignition
- Initiating cause
- material degradation (over-stress)
- Root CAUSE analysis
It is not known whether the pipe failure was due to fatigue or to a sudden overload. According to report of Lloyd, a weld neck flange should have been used instead of lap-joint flange, because the former shows higher fatigue life (approximately ten times) under cyclic operation.
- Root causes
- Date entry in HIAD
- 01/01/2020
Facility
- Application
- Chemical industry
- Sub-application
- Methanol production
- Hydrogen supply chain stage
- All components affected
pipe of a methanol synthesis gas compressor
- Location type
- Unknown
- Location
- industrial area
- Operational condition
- Description of the facility/unit/process/substances
DESCRIPTION OF THE PROCESS
The Benfield process, uses a solution of potassium carbonate solution (K2CO3) as an absorbent to eliminate CO2 from a gas mixture. The gas to be cleaned is passed at high pressure (e.g., 2 MPa) countercurrently through the K2CO3 -solution in the absorber. This becomes enriched with CO2 and partially reacts to form potassium bicarbonate (KHCO3).
Emergency & Consequences
- Number of fatalities
- 0
- Number of injured persons
- 0
Lesson Learnt
- Lesson Learnt
The recommendation of the author of the article reporting the incident was to use weld-neck flanges instead of lap-joint or stub-end flanges. The reason is the much longer lifetime under fatigue conditions of the former than the latter.
A weld-neck flange is a flange which has a pipe-formed part which is welded head-to-head to the pipe.
A lap-joint or stub-end flange use a stub-end which has to be welded on one side to the flange and to the pipe to the other side.
In-depth data
- Release type
- gas mixture (syngas)
- Involved substances (% vol)
- syngas
- Probable IGNITION SOURCE
- Explosion type
References
- Sources categories
- Scientific article
- Reference & weblink
W. D. Lloyd, Methanol synthesis gas explosion. Weld-necks flanges should be used for cyclic operation, since their fatigue life is ten times that of a lap-joint flange and stub-end combination,
Process Safety Progress 2 (1983) 120-121
https://doi.org/10.1002/prsb.720020212
