Kongsberg Simrad SN90 Reference Manual page 281

• 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
During normal use, the transducer is subjected to biological fouling. If this marine
growth is excessive, it will reduce the overall performance of your system. Whenever
opportunity arise, typically when the vessel is dry-docked, the transducer face must be
cleaned for shells and other marine growth. It is important to check the transducer for
physical damage. Any cracks, fractures or holes in the red protective coating may result
in a water leak, and a leak may cause irreparable damage to the transducer.
A transducer must always be handled as a delicate instrument. Incorrect actions may
damage the transducer beyond repair. A physical blow to the transducer face may easily
damage one or more elements. Observe these transducer handling rules:
• Do not activate the transducer when it is out of the water.
• Do not handle the transducer roughly. Avoid impacts.
• Do not expose the transducer to direct sunlight or excessive heat.
• Do not damage the outer protective skin of the transducer.
• Do not use high-pressure water, sandblasting, metal tools or strong solvents to clean
the transducer.
• Do not step on the transducer cables.
• Do not damage the transducer cables. Avoid exposure to sharp objects.
Note
A hull unit may be provided as an option. It allows you to lower and hoist the transducer.
All information and tasks related to the hull unit may be disregarded and omitted if the
SN90 system is installed without this unit.
Procedure
1 Make sure that all power to the hull unit is disconnected.
2 Make sure that you have sufficient height between the hull and the dry dock floor.
3 Lowering the transducer
381294/E
Maintenance procedures
279