Release of a Light Hydrocarbon Gas Mixture in a Chemical Product Plant
During the start-up operation (phase) of a cryogenic unit, a separator exploded, releasing ethane, ethylene, methane and hydrogen. The bursting of a tank was caused by a 1600 mm long incipient crack which had been formed at the inside of the tank along a weld line (a ferritic basis metal had been welded with an austenitic weld metal). The hydrogen induced incipient crack (cracking) was caused by the alternating load during start-up and shut-down phases in the course of the operating time.
Event Date
June 7, 1996
Record Quality Indicator
Region / Country
Event Initiating System
Classification of the Physical Effects
Nature of the Consequences
Cause Comments
The immediate cause was hydrogen induced cracking originated by the geometric form variation and the resulting plastic deformation in the area of a longitudinal seam weld. This incipient cracking was favored by the high tensile (strength) austenitic CrNiMnW weld metal with its particularly accentuated martensitic composite (mixed) zone (area) along the transition between weld metal and basis metal and was also favored by its physical characteristics which differ strongly from the basis metal. A possible root or contributing cause was lack of maintenance.
Facility Information
Application Type
Application
Specific Application Supply Chain Stage
Components Involved
cryogenic unit, separator, weld
Storage/Process Medium
Location Type
Location description
Industrial Area
Operational Condition
Pre-event Summary
At the moment of the release, the plant was in in the start-up phase of a cryogenic unit.
Lessons Learned
Lessons Learned
Unknown
Event Nature
Emergency Action
The emergency shut-down switch (automatic safety device) was activated and the on-site fire-brigade was informed. Further the air-conditioning system of the measuring control centre were shut-down as precautionary measure. The control centre and the plant were evacuated, the plant equipment was emptied and stress released.
Release Type
Release Substance
Detonation
No
Deflagration
No
High Pressure Explosion
No
High Voltage Explosion
No
Source Category
References
References
Event description in the European database eMARS
https://emars.jrc.ec.europa.eu/en/eMARS/accident/view/2f7bf3bd-14f6-f0e…
(accessed October 2020)
Event description in the French database ARIA
https://www.aria.developpement-durable.gouv.fr/accident/14666/
(accessed October 2020)