Thursday, 1 January 2015



Hydraulic symbols are used for representing components used in hydraulic circuit for a system , we must note it that these symbols will not provide the design of component but it will provide the function of component .

hydraulic circuit consist these hydraulic symbols and for understanding one hydraulic system, we will have to understand the circuit of hydraulic system .

So let us start to understand the various symbols used in hydraulic circuit 

Hydraulic Pumps and Hydraulic Motor 
Hydraulic Pump and hydraulic Motor, both are represented by one circle . Drive shaft or output shaft location will also be provided in symbol.Triangles are used inside the circle for indicating the flow of fluid . 

In case of uni-direction pump or motor , there will be one triangle and if we consider bi-directional pump or motor then there will be two triangles in side the circle.
As we use hydraulic fluid in hydraulic system , hence triangles will be filled in but for pneumatic system triangles would not be filled in.
There is one difference between hydraulic motor symbol and hydraulic pump symbol and it is the direction of fluid flow . We may see hydraulic symbols,as displayed below, for pump and motor.

Hydraulic Pump,uni-direction and fixed displacement , with electric motor 
Hydraulic Pump,Bi-direction and fixed displacement 

Hydraulic Pump,uni-direction and variable displacement
Hydraulic Pump, Bi-directional and Variable displacement
Similarly ,Hydraulic motor could also be displayed ,but the direction of flow will be opposite

Direction arrows 
Arrows are used for indicating the direction of fluid flow 

Valves Port
Valve will have following types of port

Directional Control Valve 
Directional control vales are used for controlling the direction of fluid flow . We normally used to say DC valve. DC valves are displayed by several squares those are connected with each others. These squares consist arrows and these arrows indicate the direction of flow of fluid.

We may understand following points after discussing DC valve symbols
1. Switching Positions will be displayed by squares
2. Flow direction will be displayed by arrow
3. Block ports will be displayed by lines and these lines will be horizontal

DC valve Actuating methods

There are mainly four basic methods for actuating the Directional control Valve

1. Manual

2. Mechanical

3. Pilot operated

4. Solenoid operated


Combinations of above basic actuating methods are also possible
These valve actuators are basically used for movement the spool for it's various positions.

Check Valve
Check Valve consist two port, hence it is also called as two way valve . Check valve only permit the flow in one direction and blocks the flow in opposite direction . following symbol represent the check valve.
Pilot operated check valve for closing

Pilot operated check valve for opening

Pressure control valve
Pressure control valves are used for controlling the pressure in system
There are some more hydraulic symbols those are very much important to mention here as they play a very important role for understanding the hydraulic circuit for a system

Let us move ahead towards my next post about Hydraulic system , where we will discuss Power supply unit in details

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