- Describe, with the aid of a sketch, an active tank stabilisation system.
(10)
Description (5 marks)
- The system consists of two wing tanks, one on each side of the ship, connected by a cross-duct.
- A central air chamber or control tank is fitted above the duct to regulate air pressure and water flow.
- Level sensors and a gyro sensor detect roll angle, roll velocity, and ship’s motion.
- Air valves or pumps are actively controlled to adjust the water movement between the two tanks.
- By controlling the timing and rate of flow, the water movement is kept out of phase with the vessel’s roll.
Operation (5 marks)
- When the ship rolls to port, water is forced from the port tank to the starboard tank through the duct.
- The control system regulates the air pressure/valves so that water transfer is optimised to produce a counteracting moment.
- This creates a restoring force opposite to the roll direction, damping the roll.
- Unlike a passive tank, the active system adjusts dynamically to sea conditions and ship speed.
- This results in greater roll reduction than bilge keels or passive free-surface tanks alone.
Sketch (exam-style)
Your sketch should show:
- Cross-section of vessel with port and starboard wing tanks.
- A cross-duct connecting tanks with a central control/air tank.
- Valves or regulators in the duct.
- Arrows showing water flow during roll.
- A gyro sensor/controller linked to the valves.