tially at risk. Big Oil lobbied against this doomsday argument, surely the design of these huge installations, and the plethora of safeguarding systems would restrict the potential of accidents offshore, it did not seem reasonable they argued, that events offshore could escalate such that the installation itself could be destroyed. The then UK labour government set up a committee to look at offshore safety which reported to parliament in 1980. But by that time some 80 installations were up and running. Nothing much was achieved.
Eight years later the world watched in horror as 167 workers died and a huge installation was destroyed. Big oil collectively had assured the British public that the extraction of oil and gas offshore could be done safely, no one could really challenge this although a few tried. But what happened in July 1988 was too awful to contemplate; it just wasn’t supposed to happen. No one foresaw it.
Piper Alpha was destroyed because the heat energy available was unrestricted
The catastrophic consequences of Piper Alpha could not be avoided on that fateful day because the gas stored in the incoming gas pipelines (acting as a storage tank) could not be isolated because there were no Emergency Shutdown Valves (ESDV) in the incoming gas pipeline on Piper, so the gas kept flowing onto the installation. The heat energy released from this ignited gas destroying load bearing structure in minutes, the secondary explosion was caused when the incoming pipeline failed, weakened by the intense heat. Subsequently, following the public inquiry, many measures were taken, including installing ESDV’s and other measures, to reduce the heat energy from an escalating hydrocarbon event. In future, no installation could suffer the fate of Piper Alpha. The industry had the benefit of hindsight. But Prelude turns this safeguarding feature on its head, it casts aside the minimization of heat energy philosophy as if it is no longer important.
Prelude FLNG produces and stores thousands of tonnes of LNG daily
The hull is essentially a huge area within which storage tanks for cryogenic liquids are installed. If the chilled liquids were accidentally released into the atmosphere they disperse back into methane expanding during this phase change by 600 times. But there is gas also, LPG and gas condensates. Every 7 days or so Prelude will transfer onto an LNG carrier moored alongside (ship to ship transfer between two vessels in motion) enough heat energy (when the LNG is converted back to natural gas) to power the whole of London for a week. Put another way, if Prelude was a conventional gas platform, the energy entrapped in the 300 mile gas pipeline to an LNG plant in Broome WA, would equate in heat energy terms to just a half mile of LNG in the same size of pipe. Loss of life and damage to plants handling hazardous substances onshore is minimized by physical separation to reduce the effects of escalation, the so called domino effect, and loss of life or injury to workers who would normally be restricted to that part of the process where the explosion or fire occurred. But Prelude as a floating LNG plant is supported on a bedplate (the hull) which is only 488 m by 75 m. Within this limited area this atypical LNG plant has a hotel (Living Quarters), substantial utilities to service the hydrocarbon process, some 210 – 220 ever present workers, and on top of the quarters is a helipad, where 6 times a week a return flight to the mainland is scheduled.
Prelude may not have the space to reduce risks through physical segregation
From bitter experience over the years risks (after Flixborough et al) are minimized on onshore plants handling hazardous substances through plant design and layout. Catastrophic events over the last 60 years including explosions resulting from LNG spillage suggest that if the probability of loss of containment cannot be guaranteed at such facilities, and it can’t, then the consequences of such a loss must be reduced as low as is reasonably practicable.
This is achieved mainly by physical separation. Occupied buildings