At about 8.23 pm on 1 February 1994 there was a release of reactor solution from a recirculating pump near the base of a 25 tonne ethyl chloride (EC) reactor vessel at the factory of The Associated Octel Company Ltd, Ellesmere Port, Cheshire. The reactor solution was highly flammable, corrosive and toxic, mainly consisting of ethyl chloride, a liquefied flammable gas, mixed with hydrogen chloride a toxic and corrosive gas, and small quantities of solid catalyst, aluminium chloride. A dense, white cloud soon enveloped the plant and began to move off-site.

The on-site and external emergency services were called in accordance with pre-arranged procedures for major incidents involving chemical release. Over the next one and a half hours action was taken to isolate the leak, to suppress the further release of vapour and to prevent the cloud spreading.

In spite of these attempts a pool of liquid continued to collect and at 10.08 pm the flammable vapours of ethyl chloride ignited, causing a major pool fire which was most intense at the base of the reactor. As the incident developed there were also fires at flanges damaged in the fire, including jet flames at the top of two large process vessels on the plant. Although these vessels and the reactor were protected by a fire resistant coating, there was concern at one stage that the vessels might explode and the damage extend to chlorine storage vessels on the adjacent plant.

The leak occurred at a point between fixed pipework and the discharge port of a pump recirculating liquids to the reactor, as a direct consequence of either (a) the failure of a corroded securing flange on the pump working loose; or (b) the failure of a PTFE flexible connection (‘bellows’) connecting the pump discharge to the pipe. The HSE believes the first of these possible causes was the more likely. The most likely source of ignition was an electrical control box to a compressor nearby.

KEY ISSUES:
• CORROSION / SELECTION OF MATERIALS
• DESIGN CODES – PIPEWORK
• MAINTENANCE PROCEDURES
• ISOLATION

Report: https://www.icheme.org/media/13705/the-chemical-release-and-fire-at-the-associated-octel-company-limited.pdf

Image Credit: HSE