Symbols of Hydraulic Components
Standard symbols are used in hydraulic circuit diagrams to represent various hydraulic components. These symbols help engineers and technicians understand the system layout and operation easily.
Common Hydraulic Symbols
- Hydraulic pump
- Hydraulic motor
- Directional control valve
- Pressure relief valve
- Hydraulic cylinder
- Reservoir or oil tank
- Hydraulic filter
Hydraulic Oils
Hydraulic oil is the working fluid used in hydraulic systems to transmit power. It also performs other functions such as lubrication, cooling, and protection against corrosion.
Functions of Hydraulic Oil
- Transmit hydraulic power.
- Lubricate moving components.
- Cool the hydraulic system.
- Prevent corrosion and wear.
- Seal small clearances between components.
Properties of Hydraulic Oil
- Proper viscosity.
- Good lubrication properties.
- Resistance to oxidation.
- Good thermal stability.
- Low compressibility.
Types of Hydraulic Oils
- Mineral-based oils
- Synthetic hydraulic oils
- Biodegradable hydraulic oils
Contamination in Hydraulic Oil and Its Control
Contamination occurs when dust, water, or metal particles enter the hydraulic oil. Contaminated oil can damage system components and reduce efficiency.
Methods to Control Contamination
- Use proper filtration systems.
- Maintain sealed hydraulic systems.
- Replace oil at recommended intervals.
- Use clean containers during oil filling.
Hydraulic Filters
Hydraulic filters remove impurities and contaminants from hydraulic oil to maintain system performance.
Types of Hydraulic Filters
- Suction filters
- Pressure line filters
- Return line filters
Constructional Features
- Filter housing
- Filtering element
- Bypass valve
- Indicator for clogging
Typical Installation Locations
- Between reservoir and pump (suction line).
- After the pump in the pressure line.
- In the return line before oil returns to the reservoir.
Cavitation
Cavitation occurs when vapor bubbles form in hydraulic fluid due to low pressure and collapse suddenly. This can damage pumps and other components.
Effects of Cavitation
- Noise and vibration.
- Damage to pump surfaces.
- Reduced system efficiency.
Hazards and Safety Precautions in Hydraulic Systems
Possible Hazards
- High-pressure oil leaks.
- Equipment failure due to contamination.
- Overheating of hydraulic fluid.
Safety Precautions
- Inspect hydraulic hoses regularly.
- Maintain proper oil levels.
- Avoid operating systems beyond rated pressure.
- Use protective equipment when handling hydraulic systems.
Hydraulic Reservoir and Accessories
The hydraulic reservoir stores hydraulic oil and helps in cooling and settling contaminants.
Main Functions
- Store hydraulic fluid.
- Allow cooling of oil.
- Separate air and contaminants.
Accessories
- Breather filter
- Oil level indicator
- Temperature gauge
- Drain plug
Hydraulic Pumps
Hydraulic pumps convert mechanical energy into hydraulic energy by pressurizing hydraulic fluid.
Classification of Hydraulic Pumps
Gear Pump
- Simple construction.
- Used in low to medium pressure systems.
Vane Pump
- Provides smoother flow.
- Used in medium pressure systems.
Piston Pump
- Used for high pressure applications.
- High efficiency and precision.
Pressure Relief Valves
Pressure relief valves protect hydraulic systems from excessive pressure.
Types
Direct Acting Relief Valve
- Simple design.
- Opens directly when pressure exceeds the set limit.
Pilot Operated Relief Valve
- Used for high-pressure systems.
- Provides more stable pressure control.
Pipes, Tubing, Hoses and Fittings
Hydraulic systems use pipes, tubes, and hoses to carry hydraulic fluid between components.
Constructional Details
- Pipes made from steel or metal.
- Tubes used for rigid connections.
- Flexible hoses used where movement occurs.
Minimum Bend Radius
The minimum bend radius is the smallest radius a hose can be bent without damage. Exceeding this limit may cause hose failure.
Routing Tips for Hoses
- Avoid sharp bends.
- Provide sufficient slack for movement.
- Protect hoses from heat and abrasion.
- Secure hoses properly to prevent vibration.
Conclusion
Hydraulic systems are widely used in industrial machinery due to their ability to generate high forces and precise control. Proper selection of hydraulic oils, pumps, valves, filters, and piping systems ensures efficient operation, safety, and long service life of hydraulic equipment.