What Is a Pneumatic Control Valve?

Pneumatic control valves refer to all kinds of pneumatic components that control the pressure, flow rate and flow direction of air flow in the pneumatic system and ensure the normal operation of pneumatic actuators or mechanisms. The structure of the pneumatic control valve can be divided into two parts: the valve body (including the valve seat and the valve hole) and the valve core. According to the relative position of the two, there are two types: normally closed and normally open. Valves can be divided into three types: stop, slide and slide.

Pneumatic control valve

Pneumatic control valves refer to all kinds of pneumatic components that control the pressure, flow rate and flow direction of air flow in the pneumatic system and ensure the normal operation of pneumatic actuators or mechanisms. The structure of the pneumatic control valve can be divided into two parts: the valve body (including the valve seat and the valve hole) and the valve core. According to the relative position of the two, there are two types: normally closed and normally open. Valves can be divided into three types: stop, slide and slide.

Chinese name

Pneumatic control valve

Foreign name

Pneumatic control valve

Features

Different energy used

Classification

Force control valve

Pneumatic control valves refer to various types of air pressure, flow and flow direction in the pneumatic system, and to ensure the normal operation of pneumatic actuators or mechanisms

Comparison of pneumatic control valve and hydraulic valve

(I) Different energy sources used

Pneumatic components and devices can use the centralized air supply method of the air compressor station, and adjust the working pressure of the respective pressure reducing valve according to the different requirements and control points. The hydraulic valves are provided with oil return lines to facilitate the collection of used hydraulic oil in the fuel tank. The pneumatic control valve can directly discharge compressed air to the atmosphere through the exhaust port.

(II) Different requirements for leakage

Hydraulic valves have strict requirements for external leakage, while small leaks inside the component are allowed. For pneumatic control valves, except for gap-sealed valves, internal leakage is not permitted in principle. Risk of accidents due to internal leakage of the pneumatic valve.

For pneumatic pipelines, a small amount of leakage is allowed; leaks in hydraulic pipelines will cause system pressure to drop and pollute the environment.

(Three) different requirements for lubrication

The working medium of the hydraulic system is hydraulic oil, and there is no requirement for lubrication of the hydraulic valve; the working medium of the pneumatic system is air, and the air has no lubrication, so many pneumatic valves require oil mist lubrication. Valve parts should be selected from materials that are not easily corroded by water, or take necessary antirust measures.

(IV) Different pressure ranges

Pneumatic valves have a lower working pressure range than hydraulic valves. The working pressure of pneumatic valve is usually within 10bar, and a few can be within 40bar. But the working pressure of hydraulic valves is very high (usually within 50Mpa). If the pneumatic valve is used above the maximum allowable pressure. Serious accidents often occur.

(V) Different use characteristics

Generally, the pneumatic valve is more compact and lighter than the hydraulic valve, which is easy to integrate and install. The valve has a high working frequency and a long service life. Pneumatic valves are developing in the direction of low power and miniaturization, and low power solenoid valves with power of only 0.5W have appeared. It can be directly connected with a microcomputer and a PLC programmable controller, or can be installed on a printed circuit board with electronic components. The gas-electric circuit is connected through a standard board, eliminating a large amount of wiring. Occasions such as assembly lines.

The structure of the pneumatic control valve can be decomposed into two parts: the valve body (including the valve seat and valve hole) and the valve core. According to the relative positions of the two, there are two types: normally closed and normally open. Valves can be divided into three types: stop, slide and slide.

(I) Structure and characteristics of globe valve

The valve core of the globe valve moves along the axial direction of the valve seat to control the intake and exhaust. Figure 4.2 shows the basic structure of a two-way shut-off valve. In Figure 4.2a, after the working air pressure is input at the P port of the valve, the valve core is tightly pressed against the valve seat under the action of the spring and gas pressure, and compressed air cannot flow out of the A port; After the force is applied, the valve core moves downwards and leaves the valve seat, and the compressed air can flow from the P port to the A port for output. This is the switching principle of globe valves. The valve shown in Figure 4.3 is a normally open structure. Figure 4.3a is the initial state. Contrary to Figure 4.2a, the valve core acts on the spring force.

After leaving the valve seat, the compressed air flows from the P port to the A port for output. Figure 4.3b is the working state. Under the action of the upward force of the valve stem, the valve core is tightly pressed on the valve seat to close the valve port, the flow channel is closed, and no compressed air flows out of port A.