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Hydraulic Symbols

To enable engineers to communicate and understand the circuitry associated with hydraulic systems there is an International Standard for hydraulic symbols – ISO1219/1 2006

Circuit diagrams enable the reader to identify the valve type and function and in certain cases, their locations relating to other components.

The symbols do not identify component size or their actual position on the machine however the symbols do provide vital information relating to the configurations and flow path connections.

The circuit diagram is a vital tool throughout the life of a system and should be kept up to date at all times should any modifications or changes be made to the circuit.

The circuit diagram becomes a very important document when carrying out fault-finding procedures


Hydraulic Symbols
Bladder Accumulator Branching Close Branching with connected pipe Check valve, pilot opeared Check valve without spring Check valve with spring  Compensated flow regulator, 3 way Compensated flow regulator, 2 way
Pilot operated check with drain Control for directional control valve - adjustable stroke Control for directional control valve - Cam operated Control for directional control valve - Detent Control for directional control valve - Proportional control Control for directional control valve - Solenoid Control for directional control valve - Electro hydraulic Control for directional control valve - Hydraulic
Connection point - Pipes & connections Directional control valve - Lever operated Directional control valve - Pneumatic operation Directional control valve - Push button operated Directional control valve - Spring Counter pressure valve Coupling with check Crossing - pipings & connection
Cylinder with adjustable end stroke & cushioning on both sides Cylinder with adjustable end stroke & cushioning on one side Cylinder with fixed stroke & cushioning on one side Directional valve, 2 way, 2 position  Directional valve, 3 way, 2 position  Directional valve, 4 way, 2 position  Directional valve, 4 way, 3 position  Double acting cylinder, double rod
Double acting cylinder, single rod Drain pipings & connections Electric motor Electro hydraulic proportional Engine Fast Coupling Filter Fixed diplacement motor, 1 rotation, 1 direction
Fixed diplacement motor, 2 rotation, 2 direction Fixed diplacement motor, 1 flow direction Fixed diplacement motor, 2 flow, 2 direction Flexible hose connection Flow meter Hand pump Heat exchange cooler Heat exchanger heater
Hydraulic accumulator Liquid operated cooler heat exchanger Main piping and connection Pilot pipings and connections Piston accumulator  Pressure gauge Pressure switch  Pressure reducing valve, direct operated
Pressure reducing valve, pilot operated Pressure relief valve, direct operated Pressure relief valve, pilot operated Pressurised reservoir Reservoir pipings above level Reservoir pipings under level Rotary Actuator Rotating shaft, 1 direction
Rotating shaft, 2 direction Sequence valve, direct operated Sequence valve, pilot operated  Single acting cylinder, return stroke Single acting cylinder, return stroke Spool position sensor, industive proximity sesnor Spool position sensor, micro switch Telescopic cylinder, double acting
Telescopic cylinder, single acting Temperature gauge Variable displacement motor, one rotation/direction Variable displacement motor, 2 flow direction Variable displacement pump, 1 flow direction Variable displacement pump, 2 flow direction Variable throttle valve, 2 way Variable throttle valve with check

 

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