Pressure relief valve
The most important safety valve using to hydraulic system which is called pressure relief valve. It is used to limit the maximum system pressure to keep the system safe and operational condition. Without relief valve the system pressure could build to an excessive level where machine can be damage or hose pipe can burst. So, it is very important to use pressure relief valve to the hydraulic system. Pressure relief valves is activated from its own line. In the diagram if load is exceed than set pressure relief valve will be activated and unload the excess pressure. If set pressure is 140 kg and load 180 kg then relief valve will open in 120 kg loads.
Unloading valve
Unloading valves works same as pressure relief valves. Both pressure relief valve and unloading valves send fluid to the tank during set pressure is reached. When fluid from an external line reaches a certain pressure then unloading valves opens and send fluid to the tank.Typically unload valves used in the system where two fixed displacement pumps are available. This valve protects the prime mover and save the energy.
Stage: -1: For primary extension of cylinder both pumps works synchronously that’s why cylinder moves fast.
In stage-2: When cylinder reached in set pressure (300 Psi in diagram) unloading valves opens and high flow low pressure fluids go to tank.
Stage: -3: For fully extension of cylinder back pressure will be developed at 3500 psi that’s why relief valve opens and low flow high pressure fluids redirects to the tank.
Pressure reducing valve
Pressure reducing valve is a type of pressure control valve. It can maintain constant outlet pressure. Pressure reducing valves is used to limit pressure to the branch line to a lesser amount than required in a main line. Suppose the main line pressure is 100kg and you need 50 kg in branch line. If you use pressure reducing valve it is possible to supply 50kg in the branch line.
Counter balance valve
Counter balance valve is most commonly used to create holding pressure to cylinder in resulting it prevent the load while descending. It Prevent over running load and keep the components safe. In this circuit without counter balance valve the load will fall uncontrolled and over run. To avoid uncontrolled operation we set a counter balance valve to this circuit.
Sequence valve
Pressure relief valve and sequence valve working principle is almost same.
To control two cylinder at once it is used sequence valve. As an example
if one cylinder clamping completed then start second one for
clamping. A sequence valve always has an external drain connected
directly to the tank.
Post a Comment