Event
- Event ID
- 654
- Quality
- Description
A short circuit developed in the wiring of a fire eye system on one of two 600 psig boilers serving a refinery. This triggered a rapid sequence of events that resulted in a one week shutdown of much of the refinery. Fortunately no one was injured and equipment damage was negligible.
When the hydrocracker make-up compressor started slowing down, the control system at the reformer released the excess hydrogen to the flare. However, no increase flame was observed at the flare and the crude unit pressure went over 50 psig. The trouble was quickly diagnosed as a blockage in the flare system. The hydrocracker units were shutdown. Quick action by operating personnel prevented potentially catastrophic failures to the flare system and other operating equipment.
No major leak occurred and within two hours, it was concluded that the molecular seal was plugged. Witnesses at the time of the upset observed debris flying out of the flare. A search revealed five or six ice boulders, each weighing 50 to 60 pounds at the base of the flare. Also the 3 inch centre steam pipe and nozzle was found in the area.
- Event Initiating system
- Classification of the physical effects
- No Hydrogen Release
- Nature of the consequences
- Macro-region
- Europe
- Country
- United Kingdom
- Date
- Component involved
- venting system
- Failure mode
- malfunctioning
- Initiating cause
- ice formation
- Root CAUSE analysis
The INITIATING CAUSE was a series of events starting with an electrical short circuit, causing failure of venting the excess hydrogen because the vent duct was blocked (probably by ice).
The source reports big ice blocks as the reason for blocking vent stack flow. It seems to suggest a ROOT CAUSE related to harsh environmental condition and shortcoming in design of the vent.- Root causes
- Date entry in HIAD
- 01/01/2020
Facility
- Application
- Petrochemical industry
- Sub-application
- Hydrocracking process
- Hydrogen supply chain stage
- All components affected
flare, hydrocracker, compressor and boiler
- Process temperature range [C]
- Very high temperature (500°C to 1000°C)
- Process pressure range [MPa]
- medium pressure (2 to 10 MPa)
- Location type
- Unknown
- Location
- industrial area
- Operational condition
Emergency & Consequences
- Number of fatalities
- 0
- Number of injured persons
- 0
- Post-event summary
Witnesses at the time of the upset observed debris flying out of the flare. A search revealed five or six ice boulders, each weighing 50 to 60 pounds at the base of the flare. Also the 3 inch centre steam pipe and nozzle was found in the area.
- Emergency action
The trouble was quickly diagnosed as a blockage in the flare system. The hydrocracker units were shutdown. Quick action by operating personnel prevented potentially catastrophic failures to the flare system and other operating equipment.
In-depth data
- Release type
- no release
- Released amount (kg)
- 0
- Probable IGNITION SOURCE
References
- Sources categories
- ICHEME
- Reference & weblink
Event description extracted from the UK database ICHEME in PDF
https://www.icheme.org/knowledge/safety-centre/resources/accident-data/
(accessed October 2020)
