At 6:15 p.m., a catastrophic vessel failure and fire occurred in a petroleum Separation Facility, killing 4 workers and creating significant damage (destruction of 4 personal vehicles and a backhoe, damage to oil and water storage tanks).
The facility housed two petroleum separation trains (petroleum separators connected in series) and consisted of separation equipment, piping, storage vessels, and a gas distribution system. The separation trains were designed to produce crude oil and natural gas from well fluid, derived from two nearby wells.
On the day of the incident, one of the two separation trains was to be put in operation and production was to be initiated from a new well, located 3,2 km from the facility and connected by a pipeline. Facility supervisors intended to purge the pipeline by opening the well and using well fluid to displace air out of the pipeline and through a storage tank roof hatch, located at the end of the production train. Purging is a common practice in petroleum production and processing and entails the removal of air from systems that will subsequently contain flammable hydrocarbons. This purging process was initiated and then conducted for approximately 60 minutes, at which point a separation vessel ruptured, releasing flammable gas that ignited. Gas from the ruptured vessel produced a large fireball, which damaged nearby piping and released and ignited additional flammable materials.
The separation vessel that failed lacked an inlet valve and therefore could not be isolated from an adjacent bypass line, which contained high-pressure purge gases. Two outlet block valves on the separator were closed, as were two block valves on the bypass line downstream. Accordingly the high pressure purge gases could not be vented and the separator, which was only rated for atmospheric pressure service, was exposed to about 55 bars. Since the separator was not equipped with any pressure-relief devices, the overpressurization caused the separator to fail.
The US CSB that investigated the case underlined organisational factors that lead to the accident :
- The management did not use a formal engineering design review process or require effective hazard analyses in the course of designing and building the facility.
- the operator engineering specifications did not ensure that equipment that could potentially be exposed to high-pressure hazards was adequately protected by pressure-relief devices.
- The management did not provide workers with written operating procedures for the start-up and operation of the facility.