Directional Control Valves

control valves in hydraulics

1- Directional control valves (DCV)

3/2 way - 4/2 way - 4/3 way and more

2- Flow control valves (FCV)

Check valve - one way flow control valve - two way flow control

3- Pressure control valves (PCV)

Pressure regulator - pressure relief valve - sequence valve and more

To understand more how the directional control valves are operating, please see this animation and after that you need to share with us other animations about the above mentioned valves

http://science.howstuffworks.com/engineering/structural/wave-pool6.htm

Pressure Relief Valve

The hydraulic pressure relief valve is considered to be one of the most important valves in the hydraulic systems. The PRV is playing an essential role of protecting the system from the excessive pressure that might be the main reason of collapsing the hydraulic system. To know more about the pressure relief valve, I want you all to read this article in order to recognize the wide usage as well as the importance of this valve. Yes, the pressure relief valve is used also in  Espresso machines. You are also requested to share with us other applications that use the pressure relief valve. 

http://www.frcndigital.com/coffee/opv.html