PRODUCTION/PROCESSING/HANDLING 39
Putting the brakes on subsea oil platforms for secure mooring
Brakes secure the mooring of semi-submersible oil drilling platforms. Heat dissipation capability means they can stay cool and provide fine adjustment while withstanding the huge variable forces on the cable drums.
El anclaje de las
plataformas submarinas de perforación petrolífera se asegura por medio de frenos. Su capacidad termo-disipadora implica que pueden mantenerse refrigeradas y aportar un ajuste fino, a la vez que soportan las enormes fuerzas variables en los tambores para cable.
Mithilfe von Bremsen wird das Festmachen halbtauchender
Ölbohrinseln abgesichert. Durch die Wärmeabfuhr bleiben sie dabei gut gekühlt und lassen sich feineinstellen, während sie den riesigen, veränderlichen Kräften standhalten, die auf die Kabeltrommeln einwirken.
rakes produced by Wichita Clutch, part of worldwide power transmission group Altra Industrial Motion, are being used on semi- submersible rigs for dynamic tensioning and the subsequent static holding of the anchor cables which keep the rig in position during drilling.
B
At times the cables need to reach lengths of several kilometres, meaning that the torsional load on the winch can reach several hundred tonnes. The brakes are dual action meaning that they are suitable for static holding but also to provide dynamic tension control during cable payout whilst in mooring mode, they utilise copper alloy heat transfer surfaces which provide the optimum heat dissipation for the high loads the brakes are subjected to during mooring.
Semi-submersible drilling platforms are used for exploratory drilling of potential new sights. The platforms are self-propelled and capable of drilling in depths of up to 2400 metres. Once the platforms are in position they can use dynamic positioning to remain stationary, however if the platform will remain in the same place for an extended amount of time then a mooring pattern will be laid. Due
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Fig. 1. The platforms are self-propelled and capable of drilling in depths of up to 2400 metres.
to the size of the platforms and depths that they operate in it is essential that the mooring pattern is spread, often over an area of 6km; using a series of winches and brakes to control the cable payout. A very wide spread, reaching 6km, is
necessary to ensure the platform’s stability. To achieve this spread an anchor handling vessel is used. The vessels transport the anchors, usually eight but sometimes as many as 16, away from the platform and then lay them. The payout tension has to be controlled as the anchor handling vessels move further and further away from the semi-submersible rig and cable weight increases. Each corner of the platform is typically equipped with two mooring winches which, traditionally, need two secondary brakes; one brake for static holding once the anchors are laid, and another – a slipping brake, to control the payout of the cable. Wichita Clutches Kopper Kooled dual acting water cooled dynamic brakes are able to do the job of both brakes, meaning that
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