Hydraulic Systems on Board a Vessel
(a) Four Applications for Hydraulic Systems on a Vessel:
Hydraulic systems are widely used on board vessels due to their ability to transmit high power efficiently through pressurized fluids. Here are four common applications:
- Deck Machinery: Hydraulic systems power various deck machinery essential for cargo handling and operations. This includes:
- Cargo winches and cranes: For lifting and lowering cargo containers, anchors, and other equipment.
- Mooring winches: Used for mooring and maneuvering the vessel during docking procedures.
- Hatch covers: Hydraulic systems operate mechanisms for opening and closing large hatch covers on cargo holds.
- Steering Gear: Modern ships often utilize hydraulic steering gear systems. These systems use high-pressure hydraulic fluid to move the rudder, providing precise control over the vessel’s direction.
- Stabilizers: Hydraulically powered stabilizers are deployed to reduce a ship’s roll in rough seas, improving passenger comfort and stability during cargo operations.
- Auxiliary Systems: Hydraulics can be used for various auxiliary functions on board, such as:
- Door opening mechanisms: For watertight doors, engine room doors, etc.
- Lifeboat davits: Hydraulic systems can power the davits used to launch lifeboats during emergencies.
- Windlass: Used for raising and lowering the anchor chain.
(b) Effects and Possible Causes of Contaminants in Hydraulic Systems:
Contamination within a hydraulic system can lead to several problems and malfunctions. Here’s a breakdown of three common contaminants and their effects:
(i) Air in the System:
- Effects: Air entering the hydraulic system can cause problems like:
- Spongy Operation: Air compresses more readily than hydraulic fluid, leading to a spongy or unresponsive feel in hydraulically operated equipment. This can make precise control difficult.
- Cavitation: Air bubbles can collapse under pressure within the system, creating shockwaves that damage pump components and reduce overall efficiency.
- Increased Noise: Air in the system can cause excessive noise during operation.
- Possible Causes: Air can enter the system through:
- Leaking connections: Improperly sealed connections, loose fittings, or worn seals can allow air to be sucked into the system.
- Low fluid level: If the hydraulic fluid reservoir is not properly filled, air can be drawn in as the pump operates.
- Air entrainment during refilling: Introducing new hydraulic fluid too quickly can trap air bubbles within the system.
(ii) Dirt and Foreign Particles in the System:
- Effects: Dirt and foreign particles can cause significant damage to hydraulic components:
- Abrasive Wear: Dirt particles act like sandpaper, accelerating wear on pump components, valves, and cylinders. This reduces efficiency and shortens the lifespan of components.
- Sticking Valves: Contaminants can jam or stick valves, preventing proper operation of hydraulic equipment.
- Increased System Friction: Dirt particles can increase friction within moving parts, leading to reduced performance and overheating.
- Possible Causes: Dirt and foreign particles can enter the system through:
- Contaminated new fluid: Using dirty or unfiltered hydraulic fluid can introduce contaminants.
- Improper maintenance: Failure to replace filters or maintain proper fluid cleanliness can allow dirt to accumulate within the system.
- External leaks: Leaks in the system can allow dirt and debris from the surrounding environment to enter.
(iii) Separated Water in the System:
- Effects: Water contamination in hydraulic systems can have various detrimental effects:
- Corrosion: Water can cause corrosion of metal components within the system, leading to premature wear and failure.
- Hydrolysis: Water can react with the hydraulic fluid, breaking it down and reducing its lubricating properties. This increases wear and tear on components.
- Freezing: In cold environments, separated water can freeze within the system, causing blockages and potentially damaging components.
- Possible Causes: Water can enter the system through:
- Condensation: Moisture in the air can condense within the system, especially in environments with significant temperature fluctuations.
- Contaminated new fluid: Using hydraulic fluid that already contains water can introduce contamination.
- Coolant leaks: In systems where the hydraulic fluid is cooled by a separate water-based system, a leak in the heat exchanger can allow water to mix with the hydraulic fluid.