Conoco (U.K.) Ltd. has ordered a prototype emergency escape system for its North Valiant 1 gas production platform in the North Sea.
It will be installed in 3 months, ready for trials.
The SJL-Stairway, developed by Sir James Laing & Sons Ltd. (SJL), Newcastle-upon-Tyne, England, is a collapsible series of stairs and landings held in place by four guide wires that pass through each landing to a 3 ton tensioning weight. The stairway is stowed in a housing fixed to the platform.
On release of a gravity brake, the weight is lowered to 2 m above the seabed, while the stairway descends to a predetermined level. This is calculated so the lowest two landings would be in the sea in average wave and tide conditions and no more than 2 m above sea level at the lowest conceivable tide.
Platform workers would make their way down to the landing nearest sea level and into rescue vessels or life rafts. The first option for escape from the platform is a helicopter, but there also will be fixed ladders and life rafts as well as the stairway. After use, the stairway can be winched back into the housing, immediately available for further use. Conoco is considering the stairway for use on its southern gas basin platforms. These include Viking field with five platforms and the so called Y fields with six platforms, with the possibility of use in the CaisterMurdoch field complex.
Computer modeling has shown that the sea level landing will move less than 1 m in 7 1/2 m wave conditions. Mathematical modeling, scale model construction, and tank testing have been carried out in conjunction with the Universities of Glasgow and Strathclyde.
Current research involves building a database of configurations, including number of landings, water depths, and behavior of the last landing above water. This will enable SJL to predict system performance for any combination of air gap from 10 m to 25 m and water depths of as much as 50 m.
If trials are successful, Conoco will order 12 more systems. The U.K. Health and Safety Executive is helping to fund the first installation, with an eye to judging the system's performance against recommendations of the Cullen report on the Piper Alpha platform explosion and fire.
Copyright 1992 Oil & Gas Journal. All Rights Reserved.
