- Release of toxic/flammable materials
Esso Longford Plant, Australia, 25 September 1998
A pump supplying heated lean oil to a heat exchanger stopped and was offline for several hours. There was no flow of warm lean oil though the heat exchanger causing the temperature to drop to a value which was estimated to be -480C and well below the normal operating temperature (approximately 1000C). The low temperature resulted in the formation of ice on the heat exchanger nozzle.
When the lean oil pump was restarted, it introduced a flow of warm lean oil into the exchanger. The temperature differential caused stress in the vessel resulting in its brittle fracture.
A vapour cloud upwards of 10 tonnes of hydrocarbons was released, which was ignited by heaters 170m away leading to a series of explosions and vessel ruptures.
- Assessment of hazards
- Procedures for identifying foreseeable failures with significant consequences should be developed and operators inculcated in these. At the Esso plant, a Hazard and Operability study (HAZOP) which would have identified the potential hazard was not carried out
- Management of change
- There were significant changes in operating processes, staffing and procedures at the Esso plant without thorough risk assessments being carried out for the changes.
- Training of personnel
- Personnel should be provided with training in the limitation of plant equipment.
- Adequate engineering expertise and senior supervision should be provided on-site, allowing operators sufficient technical support.
- Emergency response planning needs to be based on a review of the full spectrum of the risk profile, including alarm analysis.