Hydrocarbons Fire in a Refiner
During a work tour on a refinery, an employee noticed a fire at the level of a flange at the inlet of the grille of an exchanger, located at the outlet of a reactor of the catalytic reforming unit.The plant operator detected a lack of uniformity of torque on the bolts. Two years ago, during a shutdown period, some parts of the exchanger had been removed for inspection. The flange on the heat exchanger side was not easily accessible. On reassembly, the presence of a pipe tee near the flange made it difficult to tighten with a bolting machine. The faulty tightening (1.5 mm opening) could have led to the leakage of high-octane gasoline, mixed with hydrocarbon gases and hydrogen. Without a hot spot nearby, this 500C fluid could have spontaneously ignited on contact with air.The plant operator tightened the flange and modified procedures to specify the use of a suitable wrench for the configuration. The operator also planned to carry out independent checks on the quality of the connections made.(ARIA database)
Event Date
May 19, 2019
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 ignition of leaked mixture of hydrocarbons, including hydrogen. The intermediate or root cause could have been the lack of tightness of a flange caused by a not-properly tightening of the bolts. Finally, the contributing or root cause was the difficulty of re-assembling of the system due to design.
Facility Information
Application Type
Application
Specific Application Supply Chain Stage
Components Involved
reformer, heat exchanger, flanges, bolts
Location Type
Location description
Industrial Area
Currency
Lessons Learned
Lessons Learned
As corrective measures, the operator planned to carry out independent checks on the quality of the connections made.The quality of the event description does not allow for a detailed lesson learned. nevertheless, better operative/maintenance procedures and a (better) reporting system shall be part of it.
Event Nature
Emergency Action
Unknown
Detonation
No
Deflagration
No
High Pressure Explosion
No
High Voltage Explosion
No
Source Category
References
References
Event description no 55225 in the French database ARIA (accessed October 2021)