Accessing the installation trunk by lowering the transducer
To do a visual inspection of the inside surface of the installation trunk you need access. Access is also required to inspect and or replace the sacrificial anodes. This access can be achieved by lowering the transducer as far as it goes.
Prerequisites
The vessel is in dry dock. The SY50 system is turned off. The shipyard must provide all necessary tools and manpower.
You need a suitable spanner (wrench). You also need a torque wrench.
Two persons are needed to do the task.
•  One person must stay in the sonar room to operate the hull unit.
•  One person must stay in the dry dock, under the hull, to make sure that the transducer is not lowered too far down.
Proper oral communication must exist between the sonar room and the dry dock personnel.
Context
The transducer is covered with a thick red or black protective coating made of a special plastic type. The protective coating is a vital part of the transducer. It is very important that neither this coating nor the internal parts of the transducer are damaged during the handling, installation or cleaning. Any holes and/or scratches in the transducer surface will allow water to penetrate the transducer. If a leak occurs, the transducer must be replaced.
Procedure
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1 Make sure that the SY50 system is turned off.
2 Make sure that you have sufficient height between the hull and the dry dock floor.
3 Lowering the transducer
a Remove the protective cap on the top cover.
b Use the spanner to rotate the hoisting spindle.
c Lower the transducer to its bottom position.
Note
Locate the Lower Limit Switch. It is placed inside the bottom of the gantry. Stop the rotation when the switch is activated.
d Replace the protective cap on the top cover.
4 Accessing the trunk bearing:
a Hold the transducer shaft firmly in place to prevent it from falling down.
Do not damage the surface of the transducer shaft. If you use a mechanical device to hold the transducer shaft, make sure that the surface of the shaft is not damaged. Any dents or scratches in this surface may result in a water leak through the gaskets in the mounting flange.
b Loosen the bolt on the lifting clamp.
c Adjust the vertical position of the transducer shaft.
5 Restoring the transducer shaft to its original position:
a Adjust the vertical position of the transducer shaft.
b Make sure that the entire trunk bearing is located well inside the installation trunk.
c Make sure that the transducer shaft surface is clean from grease or other particles, then tighten the bolt on the lifting clamp.
Note
This is a critical step. The lifting clamp supports the total weight of the transducer shaft, trunk bearing and transducer. Inaccurate mounting of the lifting clamp can cause the transducer shaft to loosen. This can cause damage to the sonar system, and even to the vessel if the transducer shaft and transducer are lost. Make sure to use the wedge lock washers.
Use the following torque: 75 Nm
Note
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Make sure to use the wedge lock washers. A wedge lock washer (also known as a Nord-lock washer) is a two-piece washer with radial teeth on one side and wedging action of the halves where they join. These washers provide the highest amount of vibrational loosening prevention.
6 Hoisting the transducer
a Remove the protective cap on the top cover.
b Use the spanner to rotate the hoisting spindle.
c Hoist the transducer to its upper position.
Note
Locate the Upper Limit Switch. It is placed inside the top of the gantry. Stop the rotation when the switch is activated.
d Replace the protective cap on the top cover.
7 Make sure that the bottom of the transducer is positioned 10 to 20 mm above the bottom of the installation trunk.