The Important Hydraulic Symbols

10 May, 2010- The primary step towards studying hydraulic schematics is understanding the hydraulic component symbols. Below is the glossary for some of the basic hydraulic symbols

Hydraulic Reservoir Symbol

Each hydraulic system has a storage tank to store hydraulic fluids known as the the reservoir. It is one of the most fundamental components of a hydraulic system and is denoted as under:

Hydraulic Control Valve Symbol

A directional control valve is used to direct and control the flow of hydraulic fluid. It basically consists of four parts namely, valve spool, actuator, spring and valve body. The valve body makes the valve spool shift as per the opening and closing of valve ports for controlling the flow of fluid. The actuator and spring are instrumental in moving the spool to and fro. The graphic symbol for it is as under:



Pressure Relief Valve Symbol
Pressure relief valve keeps a check on the pressure produced by the pump as excess of pressure can spoil the complete system. The pressure relief valve is represented as under:

The fluid enters the tank when pressure relief valve or PRV is activated. The dotted line depicts the fluid pressure which acts as an actuator for PRV. In case the fluid pressure crosses a certain value the the PRV is automatically activated, making the fluid flow into the tank till the pressure is back to normal.

Hydraulic Cylinder Symbol

Another important component in a hydraulic system is the hydraulic cylinder. A hydraulic cylinder in hydraulic schematics is represented with the following symbol:

The above symbol has two ports and hence is a double acting cylinder. A single acting cylinder has one port only.

Hydraulic Pump Symbol

A hydraulic pump is called the heart of any hydraulic system. It is the hydraulic pump which develops pressure and makes the the fluid flow within the system. As a symbol it is represented as follows:

Here the angled line with a arrow indicates it as a variable displacement pump. The best part about variable displacement pump is that it can change the output flow volume without effecting the pump's RPM at all.

Conclusion

Though there's a long list of hydraulic symbols as per the ISO hydraulic symbol glossary, but by understanding the very basic five hydraulic symbols discussed above one can easily understand most of the other symbols which fall under either of the five categories.