Kongsberg EM 712, Installation Manual

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401027/B
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Note
The information here must be considered as general advice. Each EM 712 installation
must be handled separately depending on the hull design and the other electrical and
mechanical systems installed on the vessel.
Reducing flow noise
• The shape of the transducer (or dome around it) must be as streamlined as possible.
• The hull plating in front of the transducer must be as smooth as possible.
Important
Be especially aware of bilge keels and zinc alloy anodes. The keel must be rounded off
without sharp edges. Neither extruding objects nor abrupt transitions must be present.
Reducing machinery noise
• The main engine and relevant auxiliary engines and equipment must be fixed to rigid
foundations to avoid vibrations.
• Any hull structure that may vibrate should be damped or coated to reduce the
vibrations.
The use of shock absorbers or floating rafts may sometimes reduce this noise. The
structure-borne noise may be reduced by isolation, for example by providing vibration
clamping between the transducer and the hull structure.
Reducing propeller noise
• Sufficient clearance between the propellers and the hull, the rudder and the keel must
be provided.
• Place the zinc alloy anodes in places where the water flow is the least disturbed.
• Ensure that the propellers blades are correctly designed and without damages.
• The use of a baffle between the propellers and the transducer may reduce noise
appreciably.
• Static discharges caused by the rotating propeller shaft may be removed by proper
grounding or by mounting a coal brush from the shaft to vessel ground.
Reducing rattle noise
Ensure that no parts near the transducers can rattle as a result of water flow or vibrations.
Reducing interference
Interference from the transmission pulses from other hydroacoustic instruments on
board the vessel is difficult to avoid. The problem may be reduced by choosing the
working frequencies carefully and to some extent by separating the different transducers.
On vessels with a large number of separate hydroacoustic systems installed and in
Preparations