A large explosion occurred on the Saturate Gas Plant area of the site on Easter Monday, 16 April 2001 at approximately 2:20 p.m.
The first column in the plant is the de-ethaniser (W-413) which removes methane, ethane, and propane vapour from the liquid product.
This had been anticipated in the original design and a water injection point had been installed in a line upstream of the de-ethaniser.
In November 1981 a study recommended that an additional water injection point should be installed in the overheads line.
[2] The pipe could no longer contain the pressure (27.6 barg) and burst catastrophically releasing the vapour in the line, and in the upstream and downstream plant such as the de-ethaniser column.
The cloud exploded and damaged the SGP causing further release of material which ignited and led to a large fire.
ConocoPhillips (now Phillips 66) was investigated and subsequently fined £895,000 and ordered to pay £218,854 costs by the Health and Safety Executive for failing to effectively monitor the degradation of the refinery's pipework.