The Taiwan sequence valve (Sequence Valve) is a valve that controls the action sequence of the actuator in a system with more than two branch loops, which is based on the pressure of the loop.

According to the different sources of control pressure, it has internal control and external control.

The structure also has direct and pilot types.

Fig. 1. schematic diagram of sequence valve A. closed state B. open state

Working principle：

A sequence valve is a pressure control valve that controls the sequential action of the actuator by controlling the pressure in the air road. It controls the opening pressure according to the prepressure shrinkage of the spring.

When the input pressure reaches or exceeds the opening pressure, the spring is opened, so that the output is only to A, whereas A has no output.
Sequence valves are seldom used alone, and are often combined with one-way valves to form one-way sequence valves. When the compressed air enters the valve cavity from the left end, when the gas pressure on the piston 3 exceeds the force on the compression spring 3, the piston is lifted and the one-way valve is closed under the action of pressure difference and spring force.

In reverse flow, the input side becomes the exhaust port. The output side pressure will vent the one-way valve 4 from the O port. The adjustment knob can change the opening pressure of the one-way sequence valve so as to control the sequential action of the actuator under different opening pressures.

Working principle of unidirectional sequence valve A. closed state B. open state

The performance of the sequence valve is basically the same as that of the relief valve, but because of its different functions, there are special requirements for the sequence valve.

(1) in order to make the executive elements accurately perform sequential operation, the order valve has high precision and small deviation.

(2) for the accuracy of sequential operation, the leakage of valve is small when the valve is closed.

(3) for the one-way sequence valve, the reverse pressure loss and the forward pressure loss value should be smaller.

What are the main functions of the sequence valve:

(1) the sequential action of controlling multiple components;
(2) used for pressure protection circuit;
(3) prevent the cylinder piston from falling freely due to self weight and do balance valve.
(4) unloading valve is controlled by external control sequence valve to make the pump unload.
(5) the internal control sequence valve is used as the back pressure valve.