INGENIEUR
Table 3.1 : Douglas Scale from World Meteorological Organisation Sea State Code .
A complete trenching ROV system can be divided into following sub-systems :
Vehicle : This dives and does the subsea work with the jetting tools attached to it . Sometimes it will carry survey equipment , sensors , or other tools required for specific subsea operations . It is similar to work-class ROVs . In some situations , the Trenching ROV may be equipped with a set of tracks or crawler on the port and starboard sides . These can be dismantled when the vehicle operates with a pair of skids .
Launch and recovery system ( LARS ): It is crucial to have a LARS that can hold the operation steady in rough weather conditions where manoeuvring the vehicle is challenging due to the sway of the operating vessel . It has to be carefully designed to cater for harsh conditions where dynamic impacts may often occur .
Umbilical winch : This stores the umbilical that connects the vehicle with the control cabin .
The storage drum is designed according to the operating depth of the vehicle , whether it is 1000 , 2000 , or 3000 metres .
Hydraulic power unit ( HPU ): This unit operates the LARS and winch system . It has multiple control valves to operate different functions on the LARS and winch such as luff-in , luff-out , docking head lock , winch-in , winch-out , level wind left or right , etc .
Control cabin : This is the control room for the vehicle . It contains all major surface component such as transformer , power distribution unit ( PDU ), control station , recording station , communication station , etc .
Workshop cabin : This unit is used to store all important spares for the trencher operation . All major parts and consumable spares are located here .
The basic deck layout of a trenching ROV is explained in Figure 2.3 . The red line shows the main power supply from a generator set or the ship . The blue line indicates the hydraulic control
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