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2022

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Relief valve, pressure reducing valve, sequence valve

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Hydraulic valve is a component used to control liquid pressure, flow and direction in hydraulic transmission. Among them, pressure control valves alone include relief valves, pressure reducing valves, sequence valves, unloading valves, etc. This article shares the similarities and differences between the three types of pressure valves to help you quickly distinguish them.

Hydraulic valve is a component used to control liquid pressure, flow and direction in hydraulic transmission. Among them, pressure control valves alone include relief valves, pressure reducing valves, sequence valves, unloading valves, etc. This article shares the similarities and differences between the three types of pressure valves to help you quickly distinguish them.

 

3 types of pressure valves

1) Relief valve↓

The relief valve is a kind of hydraulic pressure control valve. It mainly plays the functions of constant pressure relief, pressure stabilization, system unloading and safety protection in hydraulic equipment.


2) Pressure reducing valve↓

The pressure reducing valve is a valve that reduces the inlet pressure to a required outlet pressure through adjustment, and relies on the energy of the medium itself to automatically maintain a stable outlet pressure.

                    

3) Sequence valve↓

A sequence valve refers to a valve that controls the sequence of actions of multiple actuators based on the pressure of the circuit in a system with two or more branch circuits. Depending on its function and assembly structure, different circuit functions can be realized, such as the functions of relief valve, sequence valve, back pressure valve, unloading valve and balancing valve.

                

Same point

All three types of valves are pressure control valves. Their working principles are basically the same. They all use the control pressure of pressure oil to open and close the valve port.

 

The pressure reducing valve at different points is mainly used to reduce the pressure of a certain branch oil circuit of the hydraulic system so that the branch pressure is lower and more stable than the main oil circuit pressure. Within the range of the set pressure, the pressure reducing valve is also like a relief valve. closed. However, as the system pressure increases and reaches the pressure set by the pressure reducing valve, the pressure reducing valve opens, and part of the oil will return to the tank through it (at this time, oil with a certain pressure returns to the tank, and the oil temperature of the tank will rise) , the oil pressure in this branch will not rise. The pressure reducing valve plays a role in reducing and stabilizing the pressure of this branch. The relief valve is different. It is installed at the outlet of the pump to ensure that the overall pressure of the system is stable and will not be overpressured.

It can be said that the relief valve works passively, while the pressure reducing valve works actively.


The three types of valves have slightly different functions in the hydraulic system: the relief valve plays the roles of constant pressure relief, pressure stabilization, system unloading and safety protection. The pressure reducing valve plays the role of reducing and stabilizing pressure. The main functions of the sequence valve are: 1) Control the sequential actions of multiple components; 2) Used in the pressure maintaining circuit; 3) Used as a balancing valve to prevent the cylinder piston from free falling due to its own weight; 4) Use an external control sequence valve for unloading Loading valve to unload the pump;

5) Use internal control sequence valve as back pressure valve.

 

The differences between relief valves, pressure reducing valves and sequence valves can be summarized from the following aspects: 1. Control pressure: The pressure reducing valve controls the outlet pressure to ensure that the outlet pressure is a constant value; the relief valve controls the inlet pressure to ensure that The inlet pressure is a fixed value; the sequence valve can be controlled by the inlet pressure or external pressure. 2. The valve port status when not working: the pressure reducing valve port is normally open; the relief valve port is normally closed; the sequence valve port is normally closed. 3. Valve status during operation: the pressure reducing valve is closed; the overflow valve is open; the sequence valve is open.

4. Drain port: The pressure reducing valve has a separate drain port; the sequence valve usually has a separate drain port; the leakage oil in the spring chamber of the relief valve drains to the outlet through the flow channel in the valve body.