Explosion in a Methanol Synthesis Unit
The accident happened in a low pressure methanol plant, commissioned in summer 1971 . A 6 in. pipe, below the methanol synthesis gas compressor inter-stage relief valve, failed releasing hydrogen-rich synthesis gas into the methanol area. The pipe failed at the pipe-flange junction. Syngas was ignited by an unknown ignition source and the resultant fire burned 10-20 minutes above the synthesis gas compressor. No damages to personnel are reported, even though windows were broken within a distance of 270 m, due to the explosion. It is not known whether the pipe failure was due to fatigue or to a sudden overload. According to Lloyd (see references), a weld neck flange should have been used instead of lap-joint flange; the former shows higher fatigue life (approximately ten times) under cyclic operation.
Event Date
January 1, 1983
Record Quality Indicator
Region / Country
Event Initiating System
Classification of the Physical Effects
Nature of the Consequences
Causes
Cause Comments
It is not known whether the pipe failure was due to fatigue or to a sudden overload.
Facility Information
Application Type
Application
Specific Application Supply Chain Stage
Components Involved
pipe of a methanol synthesis gas compressor
Storage/Process Medium
Location Type
Location description
Industrial Area
Consequences
Number of Injured Persons
2
Currency
Property Loss (onsite)
15000000
Lessons Learned
Lessons Learned
The conclusion of the author of the article reporting the incident is to use weld-neck flanges instead of lap-joint or stub-end flanges. The reason is the the mach longer lifetime under fatigue conditions than the latters. A weld-neck flange is a flange which has a ipe-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 flnge and to the pipe to the other side.
Event Nature
Emergency Action
Unknown
Detonation
No
Deflagration
No
High Pressure Explosion
No
High Voltage Explosion
No
Source Category
References
References
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