On 4th January 1966, an operation to drain off an aqueous layer from a propane storage sphere was attempted. Two valves were opened in series on the bottom of the sphere. When the operation was nearly complete, the upper valve was closed and then cracked open again. No flow came out of the cracked valve, so it was opened further. The blockage, assumed to be ice or hydrate, cleared and propane gushed out. The operator was unable to close the upper valve and by the time he attempted to close the lower valve this was also frozen open. The alarm was raised and traffic on the nearby motorway was stopped. The resulting vapour cloud is thought to have found its source of ignition from a car about 160 m away. The storage sphere was enveloped in a fierce fire and upon lifting of the relief valve a stream of escaping vapour was ignited.

The LPG tank farm where the sphere was located consisted of four 1200 m3 propane and four 2000 m3 butane spheres. The fire brigade arrived on site, but were not experienced in dealing in refinery fires, and it appears they did not attempt to cool the burning sphere. They concentrated their hoses on cooling the remaining spheres. About 90 minutes after the initial leakage, the sphere ruptured, killing the men nearby. A wave of liquid propane flowed over the compound wall and fragments of the ruptured sphere cut through the legs of the next sphere which toppled over. The relief valve on this tank began to emit liquid.

The fire killed 18 people and injured 81 others. Five of the storage spheres were destroyed.

KEY ISSUES:
• DESIGN CODES – PIPEWORK
• SECONDARY CONTAINMENT
• OPERATING PROCEDURES
• EMERGENCY RESPONSE / SPILL CONTROL
• DESIGN CODES – PLANT

Image Credit: Fonds Georges Vermard