FLIXBOROUGH EXPLOSION

FLIXBOROUGH EXPLOSION

At @4:53 p.m. on June 1, 1974, a huge Cyclohexane vapour cloud of about 200 m diameter and around 100 m high, rose from the Nypro Chemical plant in Flixborough, England. The base of cloud extended into the furnace area of the adjacent Hydrogen plant where it probably ignited suddenly. There was a devastating explosion of the vapours, heard 27 miles away, 28 persons were killed and over 36 injured. The 72 million dollar Nypro plant was totally destructed and varying degrees of damage to 2,488 surrounding homes, shops and factories within an eight mile radius also resulted.

 The cause of the disaster was found by the Court of Inquiry to be the failure of the 20 inch bypass pipe. The failure, as per Mr. D.M. Tucker of the Fire Research Station, was a very noisy event, specially the release of the Cyclohexane from the stub pipes and the rumbling of Cyclohexane boiling in the reactors. The vapour cloud that formed exploded after 45 seconds of the leak. The Court ultimately theorised that the 20inch assembly failed in one step because of weak points in its own design. Hence, the Court of Inquiry felt that the omissions in design consideration of the temporary modification destroyed the integrity of a well designed and constructed plant.  The Court of Inquiry concluded that "There was no Mechanical Engineer on the site of sufficient qualification, status, or authority to deal with complex or novel engineering problems and insist on necessary measures being taken". Nypro management recognised this lack and had arranged for consulting service on any modification that was identified as decidedly hazardous.

 The primary cause of Flixborough disaster was an attempt to bypass reactor No. 5. The manner of bypassing revealed serious shortcomings in management procedures. The plant integrity was destroyed. Other weaknesses were : no detailed drawing, no stress analysis of the bypass line, not following BS 3351, the bellows and bypass assembly were not pressure tested before it was fitted and the testing of the bypass at a pressure lower than the safety valve release pressure (II bar) which were the sheer foolishness.

 The three main lessons of Flixborough disaster are:

 1.         Management system deficiencies i.e. no skilled and  qualified  engineer,  no  standard modification procedure, no clearly defined role of safety officer etc.

2.         Need to notify hazards on site to the local authorities and their guidance to the industry and

3.         Restriction (licensing) on storage of hazardous chemicals on site.

 This disaster led directly to the CIMAH regulations in the UK.