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Working principle of shut-off valve

by:Sino Valves     2021-11-15

The cut-off valve is a kind of actuator in the automation system, which is composed of a multi-spring pneumatic diaphragm actuator or a floating piston actuator and a regulating valve. Receive the signal from the regulating instrument and control the cut-off, connection or switching of the fluid in the process pipeline. It has the characteristics of simple structure, sensitive response and reliable action.

The working principle of the pneumatic shut-off valve (picture)

1. The pneumatic shut-off valve has a single seat, sleeve, There are three types of double-seat (two-position three-way), and there are two types of seals: packing seal and bellows seal.

2. The multi-spring actuator is connected with the adjustment mechanism with three columns, the whole height can be reduced by about 30%, and the weight can be reduced by about 30%.

3. The valve body is designed according to the principle of fluid mechanics into a uniform cross-section low flow resistance flow channel, and the rated flow coefficient is increased by 30%.

4. The sealing part of the valve trim has two types: tight type and soft sealing. The tight type is hardfacing hard alloy, and the soft sealing type is made of soft material, which has excellent sealing performance when closed.

5. Balanced valve trim improves the allowable pressure difference of the shut-off valve.

6. The bellows seal type forms a complete seal on the moving valve stem, blocking the possibility of medium leakage.

7. Piston type actuator, with large operating force and large pressure difference.

8. The pneumatic shut-off valve adopts a soft sealing structure, and is designed with a working seal and a repair seal. The operating torque is small, the seal specific pressure is moderate, the seal is reliable, the action is sensitive, the hydraulic control is easy to realize automatic control, and the service life long.

Structural principle of pneumatic shut-off valve

The reliability of the pneumatic shut-off valve depends to a large extent on the correct selection of its structure and materials that are fully suitable for its working conditions. In operating conditions. For example, the shut-off valve can only work in two states, fully open or fully closed. When the valve disc is in the middle position in the valve seat, a large flow rate is generated due to the large pressure drop, which forms a cavitation condition, causing erosion, damaging the sealing surface of the valve disc and the valve seat, and as a result, the sealing of the closing member is lost. Due to the effect of the seepage medium on the metal, the initial small leak will quickly become a large leak.

1. The pneumatic shut-off valve is mainly composed of a pneumatic film actuator, a single-seat, double-seat valve body, a spring, and a piston.

2. The shut-off valve has a wide range of uses, which can be used to cut off gas, combustion air, cold air and flue gas.

3. Compared with straight-stroke valves (such as single-seat valves, sleeve valves, gate valves, ball valves, globe valves, etc.), quarter-turn valves have a simpler structure, more reliable sealing effect, and more superiority.

4. The soft sealing valve has the best sealing effect, but more or less unclean debris (such as welding slag, iron filings, etc.) may be left during pipeline installation and system cleaning. When they flow through the regulating valve, it is easy to scratch the soft-seal valve seat or valve core, which increases leakage and poor sealing reliability.

5. Hard sealing and hardfacing of wear-resistant alloys are the best choice for shut-off valves. This method considers the sealing performance and the service life and reliability at the same time. Although the factory index is only 10-4~10-5, it cannot achieve the effect of soft sealing and zero leakage, but it is enough to meet the requirements of strict shut-off. Durable.

6. Because the valve core and valve seat adopt a soft seal type, this product has a strict cut-off effect, and has the advantages of simple structure, small volume, reliable use, convenient maintenance and explosion-proof.

Working principle of electromagnetic shut-off valve (figure)

1. There is a closed cavity in the electromagnetic shut-off valve with through holes at different positions, and each hole is connected to a different oil pipe and cavity. There is a piston in the middle and two electromagnets on both sides. The valve body will be attracted to which side the magnet coil is energized.

2. When energized, the electromagnetic coil generates electromagnetic force to lift the closing member from the valve seat, and the valve opens; when the power is off, the electromagnetic force disappears, and the spring presses the closing member on the valve seat, and the valve cuts off.

3. When there is no pressure difference between the inlet and the outlet, after power on, the electromagnetic force directly lifts the pilot small valve and the main valve closing part upwards in turn, and the valve opens.

Structural principle of electromagnetic shut-off valve

The electromagnetic shut-off valve is a safety emergency shut-off device for combustible gas pipelines. It can be connected to the gas leakage alarm system or to the fire control and other intelligent alarm control terminal modules, etc., to realize the on-site or remote automatic/manual emergency cut-off of the gas source to ensure the safety of gas use. When a harmful strong vibration occurs, the valve will automatically close. The valve must be opened manually after manual intervention to meet safety management regulations and meet the characteristics of accident handling.

1. When the solenoid valve coil is energized, the solenoid valve opens. At this time, the input source of the magnetic switch is in contact with the output open contact, the input source and the output close contact are disconnected, and the coil remains energized. In the open state; when the solenoid valve coil is de-energized, the solenoid valve is quickly closed. At this time, the input source of the magnetic switch is connected with the output off contact, and the input source is disconnected from the output off contact.

2. When the solenoid valve coil is energized, manually open the solenoid valve and open the solenoid valve (the power consumption of the solenoid valve coil is 20W, which can be energized for a long time), and the valve remains energized for a long time. At this time, the magnetic The switch input source is connected to the output open contact, the input source is disconnected from the output close contact, and the solenoid valve is quickly closed when power is cut or lost. At this time, the magnetic switch input source and output close contact are connected, and the input source and output are open. The contact is broken.


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Sino Global Pipeline Construction Equipment Limited humbly request you to try this item in your centers and we assure you that you would be in a great pleasure with the results.
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