Visual inspection of the hull unit
A visual inspection of the hull unit is required to make sure that the unit has not been physically damaged during the installation. It is also important to check that the unit has been installed correctly.
Prerequisites
The SU90 system hardware units are installed as specified in this manual. The SU90 system is turned off. You need the following equipment:
•  Multimeter
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
1 Make sure that the hull unit is installed in the correct location, and that it is suitably oriented for easy maintenance and replacement of parts.
2 Make sure that the unit is not physically damaged, and that the surfaces and paint-work are clean without dents or scratches.
The physical handling during the installation may have caused some minor scratches to the surfaces or paint-work. This can be accepted. However, if rough handling has caused serious damage, this must be recorded with a written statement and necessary photos, so that corrective actions can be made.
3 Make sure that the unit has been identified with the relevant product label(s), and that one label includes the part and serial numbers.
4 Make sure that the physical installation of the unit has been completed.
a Make sure that the welds and brackets used to support the hull unit are substantial enough to hold the unit securely under all operating conditions.
b Make sure that the compartment ("sonar room") in which the hull unit is mounted is clean and dry.
c Make sure that ample space is provided around the unit to allow for maintenance and replacement of parts.
d Make sure that the bolts, screws or studs that have been used are all of the correct size.
e Make sure that the correct flat and shake-proof washers have been used.
f Make sure that all the nuts have been tightened properly.
g Make sure that all welds and brackets have been painted with the correct preservation medium to prevent corrosion.
5 Make sure that cable installation has been completed.
a Make sure that all cables leading to and from the unit have been properly mounted and secured.
b Make sure that enough slack has been provided on each cable to allow for maintenance and replacement.
c Make sure that the transducer cables can move freely when the transducer is lowered and hoisted.
d Repeat the inspection of the transducer cables when the SU90 system is turned on and put to operational use.
6 Make sure that the unit is firmly connected to ship's ground.
a Make sure that the unit is securely connected to the ship's ground with an earthing strap. The strap must be in addition to any incidental electrical contact made by the mounting lugs on the unit.
b Use a standard multimeter to check that the resistance between the unit and the ship's ground is approximately 0 (zero) Ω.
7 Make sure that there are no corrosive attacks on the hull unit, mounting flange, installation trunk, support brackets or other parts of the installation.
Result
Requirements Results
The hull unit is correctly installed with easy access for maintenance and replacement of parts.  
The compartment in which the hull unit is installed ("sonar room") is clean and dry.  
All cables are properly mounted with enough slack.  
The transducer cables can move freely when the transducer is lowered and hoisted.  
The welds and mechanical brackets that support the gantry are strong enough to hold the hull unit securely in place under all operating conditions. The welds and brackets have been painted with the correct preservation medium to prevent corrosion.  
There are no corrosive attacks.  
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