Understanding Ship Fin Stabilizer and Its 5 Operation

The ship fin stabilizer, situated at the bottom part of the ship’s hull, serves the crucial purpose of counteracting excessive rolling of the ship in either direction. Although many seafarers may not encounter a real fin stabilizer until the ship undergoes a dry dock inspection, it is imperative for every onboard engineer and officer to possess comprehensive knowledge about the components and functioning of the fin stabilizer system.

Main Components Of Ship Fin Stabilizer

Now, let’s delve into the main components of the ship’s fin stabilizer:

1. Fins: There are two fins, one on the port side and one on the starboard side, integrated into the hull structure of the ship. These fins are housed in a fin box and can be operated, controlled, and tilted up to +/-25 degrees.
2. Hydraulic Power Units: There are two hydraulic power units, one on each side of the stabilizer room (PS and SB). These power units are responsible for controlling the tilting and rigging motions of the fins.
3. Bridge Control Panel (BCP): The BCP, installed in the Bridge Main Control Console (BMCC), offers remote control and indicators for operating the fin stabilizer from the bridge.
4. Local Control Units (LCU): Each stabilizer room contains a local control unit. These panels provide local indication and control for the fins.
5. Main Control Unit (MCU): The MCU is another control panel located in the Engine Control Room (ECR), which allows the ship’s fins to be controlled with the same features as the bridge control unit. It includes LCU displays for both the starboard and port sides.
6. Roll Motion Sensor Unit (RMSU): The RMSU measures the ship’s roll acceleration and sends control signals to the roll control algorithm. It interfaces with the Main Control Unit (MCU) and comprises a solid-state sensor and signal conditioning electronics.
7. Fin Angle Feedback Transmitter: This component provides the fin’s angle position signal to the servo controller. A fin angle indicator, mechanically connected to the tilt cylinder piston rod, shows the fin tilt angle.
8. Stroke Control Unit (SCU): The SCU is mounted on the variable delivery pump and is responsible for driving and providing feedback on the position of the pump’s control spindle.

The Operation Of Ship Fin Stabilizer

The operation of the fin stabilizer is as follows:

1. The Hydraulic Power Unit (HPU) powers the tilting and rigging motions of the fins. It includes a high-power electric motor connected to a variable delivery piston pump and a tandem vane pump for control pressure. Another vane pump for fin rigging and pump replenishment is driven from the opposite end of the main motor.
2. The variable delivery piston pump controls the tilting of the fins. The flow rate of this pump is regulated by a rotary valve, which is positioned by the Stroke Control Unit (SCU).
3. The SCU, consisting of a servo motor and gears with an integral resolver, enables microprocessor-based control of the pump’s flow rate, thereby controlling the fin’s rotational velocity.
4. Fin rigging is controlled by solenoid-actuated valves, and the HPU also allows emergency stowage of the fin under power. Another electric motor, of lower power, is connected to a constant delivery gear pump, which is linked to an auxiliary set of solenoid-controlled valves to tilt the fin to zero angles and rig it.
5. The operation can be controlled from either the bridge or the Engine Control Room (ECR). A selector switch on the MCU control panel enables the MCU to take over as the active control station in case of BCP failure or communication issues.

Before initiating the Gyro fin Stabilizer System, the Engine Room must ensure the following preparations:

1. Verify that there are no obstructions hindering the movement of the stabilizer machinery’s parts.
2. Confirm that cooling water is flowing through the Hydraulic Power Unit’s heat exchanger.
3. Ensure that all local power isolation switches for controls and pumps are turned ON.

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