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To retract the TRU inboard, loosen the two upper M16 nuts on the top off the Tube bracket
bolts, do not loosen the Tube Bracket screws (M10) before lifting upp the TRU assembly.
TRU vertical position check
This can be done without drydocking.
If the TRU assembly stops futher down than when it is resting on the Bracket Bolts, a new
aligning of the TRU assembly has to be done, e.g. TRU seating and “SB” marking strictly to
StarBoard, decribed earlier in this manual.
Overhual and condition check-out of the Sea Valve should also be part of dry-docking
routines, this to assure that the intended use of the Sea Valve arrangement for
service/maintenance is safely provided also when the ship is afloat.
It is also recommended when maintening to check and retightening the M10 (or M12 version)
bracket screws to 35Nm or if M12 version to 57Nm.
Do not overtightening the bracket screws.
Longer periods of slow steaming at low speed and/or extended periods of
idling/berthing/anchoring (weeks/months), specifically in tropical waters, tend to result in
rapid build-up of marine growth in the TRU vicinity as well as on the sensor surface, thus the
TRU should be retracted for inspection/cleaning and/or diver assisted under hull cleaning.
Generally, also under normal sea-going operations, it is recommended to retract the TRU for
inspection and cleaning as necessary each 3 to 6 months in order to prevent marine growth
which may affect the speed log functionality and accuracy/reliability.
Also this routine serves as condition checks and maintenance of the Sea Valve arrangement.
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