These symbols provide a consistent method of documenting hydraulic systems so that they can be easily understood by engineers and technicians. Below is a list of common hydraulic schematic symbols, categorized by component type:
1. Pumps and Motors
Fixed Displacement Pump: A circle with an arrow pointing outwards.
Variable Displacement Pump: A circle with an adjustable arrow.
Fixed Displacement Motor: A circle with an arrow pointing inwards.
Variable Displacement Motor: A circle with an adjustable arrow pointing inwards.
2. Valves
Directional Control Valve (4/3 Valve): A box divided into three sections with arrows indicating flow directions.
Pressure Relief Valve: A valve symbol with an arrow and a spring.
Pressure Reducing Valve: Similar to a pressure relief valve but with an additional line indicating reduced pressure.
Check Valve: A triangle within a circle, pointing in the flow direction.
Flow Control Valve: A square with an arrow through it, sometimes with an adjustable indicator.
3. Actuators
Single-Acting Cylinder: A rectangle with a single arrow indicating the direction of movement.
Double-Acting Cylinder: A rectangle with arrows at both ends indicating movement in both directions.
4. Reservoirs and Accumulators
Reservoir: A rectangle or a trapezoid with lines indicating fluid levels.
Accumulators: A circle with a spring inside or a line across the middle.
5. Filters
Filter: A diamond shape with a line through it.
6. Lines and Connections
Working Line: Solid line.
Pilot Line: Dashed line.
Drain Line: Dashed line with an arrowhead.
Flexible Line: A solid line with a series of loops.
7. Miscellaneous Symbols
Pressure Gauge: A circle with a pointer.
Temperature Sensor: A circle with a "T" inside.
Flow Meter: A circle with an "F" inside.
Detailed Symbols
Pumps and Motors
Fixed Displacement Gear Pump: A circle with a gear symbol.
Fixed Displacement Vane Pump: A circle with a vane symbol.
Fixed Displacement Piston Pump: A circle with a piston symbol.
Variable Displacement Piston Pump: A circle with an adjustable piston symbol.
Directional Control Valves
2/2 Way Valve: A box with two positions and two ports.
3/2 Way Valve: A box with three positions and two ports.
4/2 Way Valve: A box with four positions and two ports.
4/3 Way Valve: A box with four positions and three ports.
Flow Control Valves
Throttle Valve: A symbol with an adjustable arrow, often with a dot indicating adjustability.
Non-Return Flow Control Valve: A combination of a throttle and a check valve symbol.
Standards
ISO 1219-1: This standard outlines the symbols for hydraulic diagrams.
DIN 24300: This German standard provides additional symbols and specifications.
Understanding these symbols requires familiarity with their standardized shapes and meanings. These symbols are essential for designing, troubleshooting, and maintaining hydraulic systems effectively.
