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