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Maintenance procedures
Preventive maintenance
Preventive maintenance procedures
Inspecting and replacing sacrificial anodes
Sacrificial anodes are used to protect the hull unit and the installation trunk from corrosion. They are mounted under the mounting flange at the top of the installation trunk. Additional sacrificial anodes may have been mounted by the shipyard during the installation of the ST90 system.

About this manual
The purpose of this publication is to provide the descriptions, procedures and detailed parameter explanations required to allow for safe and efficient use of the ST90 system. The publication also provides you with a thorough understanding of the parameters and adjustments provided by the ST90 system.
Simrad ST90
Operating procedures
Maintenance procedures
- Lowering and hoisting the transducer from the sonar room
- Setting up the interfaces to peripheral devices
- Inserting the installation parameters
- Installing and maintaining software
- Testing the noise conditions and the sonar functionality
- Preventive maintenance
  - Preventive maintenance schedule
    In order to secure a long and trouble-free operation of the ST90 system, certain specific preventive maintenance tasks must be done. The tasks are organized in a preventive maintenance schedule.
  - Requirements for personnel and tools
    All tasks can be done by the crew.
  - Approved anti-fouling paints
    The list of approved anti-fouling paints can be found on our website. Always refer to the manufacturer's documentation and data sheets for a complete procedure and for relevant safety information.
  - Preventive maintenance procedures
    - Making sure that the environmental conditions in the sonar room meet the requirements
      It is important that the sonar room is kept clean and dry. The system units must not be exposed to excessive temperatures, moisture or humidity. Such conditions can cause corrosive attacks and subsequent failures to the electronic circuitry. Visit the sonar room at regular intervals to check for dust, high temperature and humidity.
    - Inspecting and cleaning the display
      To ensure long and trouble-free operation of the display, it must be inspected and cleaned at regular intervals.
    - Inspecting and cleaning the Processor Unit
      To ensure long and trouble-free operation of the Processor Unit it must be inspected and cleaned at regular intervals.
    - Inspecting and cleaning the Operating Panel
      To ensure long and trouble-free operation of the Operating Panel it must be inspected and cleaned at regular intervals.
    - Inspecting and cleaning the Transceiver Unit
      To ensure long and trouble-free operation, the Transceiver Unit must be inspected and cleaned at regular intervals.
    - Visual inspection of the hull unit
      Regular inspections of the hull unit is required to make sure that it operates properly.
    - Visual inspection of the installation trunk
      All surfaces that are in contact with seawater are exposed to marine growth (biological fouling). This includes the hull plating, the blister and the installation trunk. Marine growth inside the installation trunk can damage the transducer. Excessive marine growth on the hull plating close to the transducer can cause noise. Every time your vessel is in dry dock, you must remove the marine growth.
    - Inspecting and cleaning the transducer face
      Marine growth (biological fouling) on the transducer face reduces the performance. For this reason, it is important to keep the transducer face clean. Every time your vessel is in dry dock, you must remove the marine growth. At the same time, you must inspect the transducer closely for physical damage.
    - Painting the transducer face
      Marine growth (biological fouling) on the transducer face reduces the performance. We suggest that you paint the transducer face immediately after installation, and then again as often as required to maintain the protection. It is particularly important to do this if you operate in waters with a lot of marine growth.
    - Inspecting and replacing sacrificial anodes
      Sacrificial anodes are used to protect the hull unit and the installation trunk from corrosion. They are mounted under the mounting flange at the top of the installation trunk. Additional sacrificial anodes may have been mounted by the shipyard during the installation of the ST90 system.
    - Lubricating the hoisting spindle
      The hoisting spindle is positioned between the gantry and the transducer shaft. The top of the transducer shaft is mounted to the hoisting spindle with a lifting clamp. When the hoisting spindle turns in either direction the lifting clamp moves up and down, and so does the transducer shaft with the transducer.
    - Lubricating the transducer shaft sleeve
      The transducer shaft sleeve is a vital part of the hull unit. It supports the transducer shaft, and allows the shaft to move down and up to lower and hoist the transducer. The transducer shaft sleeve is filled with grease. The grease ensures that the vertical movement of the transducer shaft is not limited by friction. The grease also ensures that the entire construction is waterproof.
  - Accessing the inside of the installation trunk
User interface
Menu system
Functions and dialog boxes
Concept descriptions
Technical specifications
The technical specifications summarize the main functional and operational characteristics of the ST90 system. They also provide information related to power requirements, physical properties and environmental conditions.
Datagram formats
The ST90 system can send and receive information to and from several different peripherals. All transmissions take place as datagrams with data sentences. Each datagram has a defined format and length.
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Inspecting and replacing sacrificial anodes

Sacrificial anodes are used to protect the hull unit and the installation trunk from corrosion. They are mounted under the mounting flange at the top of the installation trunk. Additional sacrificial anodes may have been mounted by the shipyard during the installation of the ST90 system.

The vessel is in dry dock. The ST90 system is turned off. No special tools are required for this task. If the sacrificial anodes need to be replaced, you will need the necessary spare items as well as mounting materials. Contact your local dealer or distributor, or the Kongsberg Discovery support organization, for spare parts.

Kongsberg Discovery part number: 629-204660
Mounting bolts: M8x40
Spring lock washers
Nuts

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.

Sacrificial anodes are slowly disintegrating during normal wear and tear. They must be inspected whenever the vessel is in dry dock. If the sacrificial anodes are damaged or severely corroded you must replace them. We recommend that the sacrificial anodes are replaced when 1/3 of their bodies have been spent.

Procedure

Make sure that all power to the hull unit is disconnected.
Access the location of the sacrificial anodes.
They are mounted under the mounting flange at the top of the installation trunk.
Accessing the inside of the installation trunk
Inspect the physical conditions of the sacrificial anodes.
Check for damage and corrosion.
Replace the anodes if they are severely corroded.