entially 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 such as control rooms, workshops, warehouses and admin blocks are remotely located, or protected by the natural topography of the side, or man made earthwork, or other means to divert pressure waves. Fire breaks should contain the fire to the module or area affected. Onshore plants handling hazardous substances can often be scattered over an area measurable in square miles. So given that the probability of loss of containment cannot be reduced to negligible levels, onshore plant design and layout restricts the potential consequences of such an event should it occur?
Shell accepts that the Prelude LNG facility would normally occupy an area 4 times greater than it does if on land. But taking the example of a modern day plant complying with UK standards and Codes of Practice, and the results of Social Impact studies etc, the facility at Mossmorran covers a substantial area (this Esso/Shell plant is of course more than a LNG plant but it is an excellent example of where space and topography is used not only to reduce risks at the plant, but to facilities and people outside the plant boundaries). The Shell section of the plant is 5 miles from its Braefoot Terminal jetty with the storage tanks containing chilled liquids circa ½ mile from the jetty. The reality is that an LNG plant on land could cover a considerable land area much greater than an area 4 times the size of the Prelude deck space.
These factors conspire together to increase the potential loss of life on Prelude especially when the total population required to operate, service and maintain this facility live, work and sleep within the plant boundaries, and, the plant is 300 miles from the nearest town
The LNG industry itself accepts this argument. Studies carried out have determined that the highest risk category for an LNG or LPG FPSO is the collective risk to onboard workers. Various media outlets suggest Prelude will have manning levels around 200. On land, an LNG plant has a dayshift and nightshift; staff go home at the end of their shift which reduces