A Pressure relief valve is called safety valve in some occasion, it really protect hydraulic system or other hydraulic components. The valve is like a guard keeping an eye on a doors. The guard should be flexible and strong enough to deal with different stages of alarm.  – finotek.com

These are valves used to prevent too much pressure that may occur in hydraulic systems. Normal hydraulic pressure ranges from 900 pounds per square inch to over 6000 pounds per square inch. Excessive pressure may cause a rupture in the system hence hazardous to the personnel manning the system. A ruptured hydraulic pressure relief valve may also cause damage to the hoses, hydraulically driven motors or cylinder.

Types of Hydraulic Pressure Relief Valve

Generally there are three types of hydraulic pressure relief valve. There main function is to relieve pressure in a hydraulic pressure by opening to release excessive pressure. When the pressure rises to dangerous level the valves opens. The three types of valves are: Direct acting pressure relief valve, Pilot operated pressure relief valve and the direct operated pilot type pressure relief valves.

Construction of the Hydraulic Pressure Relief Valve.

Construction of the hydraulic pressure relief valve is one of the most complicated task in the engineering sector. Relief valves must be strong to withstand high pressure. They must be able to provide a port for removing the removed fluid. It should be able to connect itself to the hydraulic system. The hydraulic pressure relief valve must be able to open with ease when the relief pressure is attained and close smoothly when the pressure falls. 
Some advanced hydraulic pressure relief valve have the ability to collect hydraulic fluid and store it a reservoir tank so that it may be re-used in future.

Regulation of the Hydraulic Pressure Relief Valve

An average hydraulic pressure relief valve should posses a tap that is able to sense pressure. It should be able to accommodate a pressure gauge and a means of installing a relief pressure. The hydraulic pressure relief have an adjusting knob that prevents drift in its setting.

How does a Pressure Relief Valve works?

A typical hydraulic pressure relief valve works by making use of an internal spring. The hydraulic pressure relief valve gets engaged when the spring is compressed by the hydraulic fluid. When the hydraulic system reaches to unsafe level, the system works by opening up.

Direct acting valves have a system where the pressure pushes directly against the spool or the piston. The piston is held by a spring which forces the valve to open when the pressure becomes greater than the spring force. In the direct operated type, pressure at the valve opens a valve that in turns opens a relief valve. In a pilot-type valve it operates the same way except that the pressure towards the pilot valve comes from a different location in the hydraulic system.

Hydraulic Pressure Relief Valve Troubleshooting

Hydraulic pressure relief valves may encounter problems for numerous reasons, these problems can often be resolved with the help of some basic troubleshooting techniques. 

The most common problems encountered in hydraulic pressure relief valve are clogged valve, stuck valve piston and a seat failure.

    A clogged valve may occur as a result of sediment in fluids, sludge or dirt overtime. This may render the valve useless since the valve is less partially opened. Getting rid of obstructions may restore the proper functioning of the valve.

     Stuck valve may occur as a result of a malfunction spring resulting to low pressure. This necessitates replacement of the hydraulic relief valve to restore its proper functioning.

     Seat failure may occur as a result of impaired piston function. This may be indicated by chatter or noise during operation. The operator should replace the valve to solve the problem.