Troubleshooter
Normally Open Pressure Reducing Valves
Through this page, I try to make a short description about pressure reducing valve although the subject is familiar. If google it sure it will find some good information about it.
Pressure reducing valve are the only pressure control valves that are normally open. The valves may be either direct operated or pilot operated.
Direct operated reducing valves
A normally open pressure control valve has primary and secondary passages connected. Pressure at the bottom of the spool is sensed from the pilot line which is connected to the secondary port.
In contrast to pressure relief valves which affect the input pressure (pump pressure), pressure reducing valve are used to influence the output pressure (actuator pressure).
Figure above is a simple reducing valve use in hydraulic. Two forces act continually upon the pilot piston, the spring tension to the right and the pressure in passage way A to the left.
If the pilot pressure on the left of the pilot piston is higher than the set spring tension, piston will then move against the spring tension right side, thereby throttling passage way A.
The pilot piston will shift to right when the pressure in A is reduced at set pressure and is thus equal once again to spring tension. The pressure behind the pilot in passage A is equal to the spring tension. If pressure in A increase further pilot piston is pushed more against spring. Therefore channel A is connected to tank. As much fluid flows to the tank as is required to prevent pressure increasing any further.
The post is filled under Hydraulic Basic
