Escape systems from offshore installations can themselves be a liability to human health, if evacuees hit the water too fast or at the wrong angle. Several new initiatives are under way to tackle this problem in Europe and Canada. Lifeboats are normally mounted parallel to the sides of an installation and lowered by fall wires from a davit on the muster deck. There is the risk, though, of the lifeboats not clearing the installation and therefore suffering impact damage.
A possible solution is Seascape, developed by Seascape Systems of Newfoundland. This comprises a deployment arm, a winch and a TEMPSC survival craft. On a semisubmersible, the arm's base is supported at two pivot points on a transverse tubular, either at the stern or bow. The arm extends up to deck level where its peak supports the craft - so positioned as to point away from the installation.
The TEMPSC is also mechanically pivoted, allowing zero-degree trim to be maintained constantly during launching. Both the craft and deployment arm are held in place by a cable extending from a special winch (located on the deck) to the arm's upper point.
Seascape funding has come from various Canadian organizations as well as BP, British Gas and Britain's Health & Safety Executive (HSE). Humberside Offshore Training Association on the English east coast uses a Seascape system in its training programme.
Norway's Harding Watercraft has developed a new lightweight freefall lifeboat seating 18 people. Prototype tests proved it could be dropped from heights up to 40 metres without hitting the sea too hard.
Originally, the craft was designed for not normally manned installations, but the 18 seats match existing helicopter capacity. Costs are claimed to be substantially lower than existing crafts used, for instance, on Statoil's Gullfaks and Sleipner A platforms.
Chutes and stairways
The rise of floating production vessels has also imposed demands on suppliers of alternative escape systems. Selantic Safety's first order in this market came from FELS, Singapore for Statoil's Norne monohull FPSO.
Selantic is providing two evacuation systems, each incorporating the Selantic chute, a 25-person boarding platform, four 20-man liferafts, a stabilizing weight and a hydraulic power pack to allow recovery of the system after deployment.
For this ship-shaped installation, the system has to be compact, light and neatly stored in-board, but also quickly and simply moved into a cantilevered position during deployment. During operation, 15 people per minute should be able to evacuate the vessel safely into one of the four liferafts.
In Britain, the HSE has also supported development of collapsible stairways and escape chutes, following Lord Cullen's recommendations to investigate the practicality and safety of these systems. Successful trials of two systems have recently been completed.
Telescape, made by a company of the same name in Great Yarmouth, is a telescopic chute which conveys evacuees rapidly to sea level in a collecting pontoon before transferring them to liferafts or fast rescue craft. Telescape is containerized, with a fixed or compliant boom.
Scale model testing, onshore trials and offshore trials on the Santa Fe rig Britannia have proven the system's potential as a secondary means of escape. Backing has been provided by Total Oil Marine as well as HSE.
Chutes and collapsible stairs have an advantage over fixed stairs or ladders in that they are positioned away from the platform - hanging from an overhang or cantilever. They also avoid the difficulties that seem to be inherent with use of knitted ropes.
SJL-Stairway is a stair system developed by Sir James Laing & Sons, Newcastle for a range of environmental conditions on the UKCS. A prototype was built for Conoco UK's North Valiant 1 platform, receiving Type Approval from Lloyds Register. It consists of a series of platforms supported by chains and linked by integral stairs.
When not deployed, it is collapsed and stored in a housing at deck level. During deployment (which can be controlled remotely from a standby vessel or host platform), it extends under its own weight in a controlled manner.
Stability is effected by four guide wires passing through each platform and attached to a weight deployed at a set water depth - the mass of which is a key factor in the system's performance.
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