Hull Unit description
The hull unit is used to lower the transducer down below the ship’s hull when the SU90 system shall be used. When the SU90 system is turned off, the transducer is hoisted for protection. The hull unit is large and crucial part of the sonar system.
The hull unit is a mechanical construction. It is mounted on the top of the installation trunk. The installation trunk penetrates the ship’s hull, and allows the transducer to be lowered into the sea. The hull unit is normally located in the forward part of the vessel. This location is recommended to avoid the noise from the propellers and the engine.
Caution
When the transducer is lowered, the depth of water under the vessel must be monitored closely.
If the transducer hits larger objects or bottom, the transducer shaft may be bent, or - in worst case - it can be broken off. A broken transducer shaft will cause water leakage through the top of the shaft. If you suspect that the transducer shaft is seriously damaged with holes, do not retract the transducer to its upper position.
To prevent serious damage to the vessel or the vessel stability, you must have a water pump and a warning system in the sonar room.
If you forget to hoist the transducer before the SU90 system is turned off, the transducer is hoisted automatically before the power is disconnected. The transducer is also hoisted automatically if a serious malfunction occurs to the communication between the bridge and the hull unit.
In the event of improper operation, the powerful electric motor on the hull unit may cause serious damage to the equipment and/or injury to personnel. Therefore, before you start manual operation, read carefully through the relevant operating procedures. You must familiarize yourself with the correct handling methods and the relevant safety requirements.
The SU90 system can be provided with one of the following hull units:
Hull Unit Lowering depth (m) Transducer cable (m) Maximum speed (knots)
SU92 1.2 4.6 21
7
SU93 1.6 4.6 16
7
SU94 2.1 4.6 11
7
The same transducer is used on all hull unit types.
If a Hull Unit Controller is supplied with the system, the Motor Control Unit cabinet is used as a junction box.
On some vessels, additional transducer protection is required. One example is vessels working in arctic conditions. It is important for them to prevent ice from damaging the transducer. A gate valve is then added to the hull unit installation. By means of a mechanical construction it shuts off the bottom of the installation trunk when the SU90 system is not used.
For more information, refer to the end-user documentation provided by the manufacturer.
Important
The hull unit gantry must be secured to the bulkhead by means of mechanical support brackets. The dimensions and strength of the support brackets must be adequate to prevent vortex induced vibrations. This is an invariable requirement to ensure the safety of the SU90 system and the vessel.
We recommend that support brackets are placed pointing at minimum three directions with approximately 120 degrees between them.
The mechanical support brackets must be designed and manufactured by the installation shipyard to fit the complete installation in the sonar room. All calculations made to support the design must meet the applicable safety requirements, and apply to the physical properties of the complete installation.