Shell Prelude: A cause for celebration or concern?

Prelude stores thousands of tonnes of LNG and LPG with an almost constant and simultaneous operation of loading this product onto carrier vessels moored alongside. So any Safety Case has to look at the combined risks of Prelude and the carrier vessel moored alongside.

BP Texas City Refinery Explosion March 2005

Fourth in a series of articles by Bill Campbell (right), retired HSE Group Auditor, Shell International, about safety issues relating to the Shell Prelude FLNG project

John

Hope you find this interesting, perhaps your contributors can answer the question posed at the end.

When I started to write these articles I was struck by the manner in which Prelude FLNG as a hazardous substances plant turned the conventional wisdom of plant design and layout on its head.  Could such an installation be approved in the offshore UK for example?  A hypothetical question but one worthy of an answer.  I don’t believe it could. After all the Health and Safety Regulator in the UK, the custodian and owner of the many British Standards and codes for the design and layout of onshore hazardous substances plants, is the same Regulator for the offshore oil and gas industry. This is also the same Regulator that followed up on Cullen’s recommendation and put in place a suite of legislation requiring offshore installations to restrict the heat energy in an emergency, so ensuring hydrocarbon events could not escalate to threaten the newly installed temporary refuges. Prelude stores thousands of tonnes of LNG and LPG with an almost constant and simultaneous operation of loading this product onto carrier vessels moored alongside. So any Safety Case has to look at the combined risks of Prelude and the carrier vessel moored alongside.

I covered all this in an earlier article in more detail.  There appears to be something absurd about the abandonment of these design conventions (developed as they were post catastrophic incidents) because of expediency. Particularly placing hundreds of workers at risk because they will constantly occupy a building resting on the hull where the LNG and LPG are stored.

In looking for an example to support my concerns, again a factual example, not a figment of imagination, we should refer to the March 2005 Texas City Refinery Explosion.  The plant was built in 1934 and by all accounts it was not in good condition.  It was at the time the third largest US refinery however and took up a considerable surface area.  The loss of life when heavier than air hydrocarbon vapours ignited should have been restricted to the operator who got out of his pick-up truck, leaving the engine running, (thought to be the source of ignition) to go up the tower to see what the problem was.  There was a significant distance between the seat of the explosion and permanently installed occupied buildings, very few souls should have been at risk if the plant had been operating in compliance with the applicable laws.

Why then were there 185 casualties, some 15 fatalities and 170 injured, many seriously?

Well it’s all down to expediency, a means to an end, the plant needed major modifications, it needed large numbers of staff with contractors, workshops etc, air conditioned trailers so these were assembled, a sort of gypsy encampment only 350 feet from the seat of the explosion in a hazardous area.  The change control process which allowed the siting of the contractors trailers in this location was issued in 2004 and justified on the grounds that the risks were acceptable given the unlikely probability of a loss of containment and an ignition of same.

BP, the owner and operator of the plant at the time, was heavily criticised for many aspects of this disaster, charged with criminal neglect including allowing this unlawful assembly so near to the hydrocarbon process.  This is a perfect example of why the rules related to separation distances between hazardous substances modules and equipment, storage tanks, occupied buildings etc were put in place. Looking back at this incident it is almost unbelievable that the decisions to locate 200 or so contractors in ever present danger could have been considered, but when the job needs to get done, and time is money, and setting up within the plant would ensure better progress, then humans react to the pressures they are under, getting on with the job drives behaviour.

So if these isolated gas reserves have to be extracted we turn design conventions on their heads. Prelude FLNG/FLPG will not only be the biggest offshore installation in the world, it will be by an order of magnitude the most complex.  Gas treatment and compression prior to the gas going to the refrigeration process, probably a twin process to handle the volumes, LNG, when in the tanks constantly maintaining its cryogenic state by constantly venting the evaporating gas, auto refrigeration meaning this process is constantly live, LPG with its own intrinsic dangers, 6 gas fired boilers, 100 MW of installed capacity and all on an installation that will remain fully manned even under cyclone conditions.

Makes me wonder if Prelude should be a cause for celebration or concern.  What do you think?

Bill Campbell

Shell Prelude FLNG: loss of containment of hydrocarbons almost inevitable: 21 Feb 2014 (first Prelude article by Bill Campbell)

Tales of the Unexpected and Royal Dutch Shell Prelude FLNG: 28 March 2014 (Second Prelude article by Bill Campbell)

Shell Prelude: Tales of the Unexpected – When the party ended with a bang!: 2 April 2014 (Third Prelude article by Bill Campbell)

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