Dynamic Positioning DP Basic
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Light Taught Wire (LTW) (LWTF)
The use of taught wires as a position reference system.
The Taut Wire is a position reference system is designed for mounting on dynamic positioned surface vessels. Its purpose is to provide accurate data of the vessel’s movements in relation to to the position of the clump or depressor weight on the sea bed.

Light taut wire, L.T.W. or L.W.T.W. The oldest position reference system used for DP is still very accurate in relatively shallow water. A clump-weight is lowered to the seabed. By measuring the amount of wire paid out and the angle of the wire by a gimbaled head, the relative position can be calculated.

The Taught Wire is maintains a constant tension by means of a depressor weight lowered to the sea-bed and an electric servo-assisted and pneumatic tethering or mooring system. Movement of the vessel will cause the tensioned wire to deviate from its initial inclination. This movement activates Potentiometer mounted in the gimbaled (sensor) head and produces changes of analogue signals directly proportional to the deviation in inclination.

Care should be taken not to let the wire angle become too large to avoid dragging. For deeper water the system is less favourable, as current will curve the wire.

It is not unusual for pipe lay and construction vessels to use two Taught Wire Reference systems in tandem.

Planning is of the utmost importance when considering using LTW. The nature of the seabed needs to be accurately assessed. Also it is important to know what obstructions and sub sea hardware is on the operational site. Where possible the LTW on the outboard side of an operational vessel should be deployed when working close to a structure.

Good communications are essential particularly if the operation will involve divers or ROV operations

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Light Taught Wire (LTW) (LWTF)