The single seat pneumatic control valve does not move, that is, the valve does not move and there is

There is an explanation on the official website of Shanghai Lidian solenoid valve, there are two reasons, the first is that the middle engine of the positioner is blocked, or there is a large amount of water accumulated next to the amplifier ball valve. The second is the problem of the valve core, either the valve core falls off, or it is stuck, or the actuator is faulty, and these reasons will cause this problem. The valve will also have a loud noise, that is, there is a sound of chirping, which is mainly because the control valve is selected to be large or the degree of opening is relatively small, and then there is a sound that the support is not reliable and can not be well supported.

Here are some of the well-known brands recognized in the valve industry, which are widely recognized and have a high reputation. While rankings may vary depending on time and market conditions, the following brands are generally considered to be among the top brands in the valve industry:

The following influential first-line brands of water system valves and industrial valves can be used as a reference, but for reference only: Suzhou Neway Valve, Shanghai Guanlong Valve, Shanghai Qizhong Valve, Sanhua, Su Yan, Shentong, Su Valve, Nanfang, Jiang.

First, the word Yao. The above manufacturers are only estimates and references, and the specific situation may vary or fluctuate at any time due to changes in a series of factors such as changes in the market, the size of the competition pattern, and the stability of product quality. As an indispensable key device in industrial production and civil facilities, the quality and reputation of the valve brand directly affect the satisfaction and trust of users.

These brands are known in the valve industry for their innovative technology, high-quality products and reliability. It is important to note that the market and industry are evolving rapidly, and different rankings may vary depending on time and region. For the most up-to-date ranking information, it is recommended to refer to industry reports, professional organizations or market research data for more detailed and accurate information.

Check whether there is a problem with the signal of the positioner, check whether there is a problem with the air source, see if the inner diaphragm of the actuator is damaged, see if there is a foreign object stuck in the valve, and check the cause one by one. Hope it helps.

If you have a problem with the locator, you can change the locator or see if the wire is wrong.

(1) The regulating valve does not operate. The fault symptoms and causes are as follows:

1 No signal, no air source. The air source is not opened, due to the water content of the air source freezing in winter, resulting in the blockage of the air duct or the blockage of the filter and pressure reducing valve, and the failure of the compressor; Leakage of air main.

2 There is an air source, but no signal. Regulator failure, signal tube leakage; Positioner bellows leakage; Damage to the adjusting omentum diaphragm.

3 The positioner has no air supply. clogged filters; Faulty pressure reducing valve leaking or clogged pipes.

4 The positioner has an air source and no output. The throttle hole of the positioner is blocked.

5 There is a signal, no action. The valve core falls off, and the valve core is stuck with the society or with the valve seat; bent or broken stems; Frozen or coke dirt from the seat, spool, and spool; The actuator spring rusts due to long-term use.

2) The action of the control valve is unstable. The fault symptoms and causes are as follows:

1. The pressure of the air supply is unstable. The compressor capacity is too small; Failure of the pressure reducing valve.

2 The signal pressure is unstable. The time constant (t=rc) of the control system is inappropriate; The regulator output is unstable.

3. The air source pressure is stable, and the signal pressure is also stable, but the action of the regulating valve is still unstable. The ball valve of the amplifier in the positioner is not tightly closed by dirt wear, and the air consumption is particularly increased, and the output will be generated**; The nozzle baffle of the amplifier in the positioner is not parallel, and the baffle cannot cover the nozzle; air leakage from output pipes and lines; The rigidity of the actuator is too small; The friction resistance of the stem is large during the movement, and there is a blockage phenomenon with the contact part.

c) Vibration of the regulating valve. The fault symptoms and causes are as follows:

1 The control valve vibrates at any opening. unstable support; There is a vibration source nearby; The spool and bushing are heavily worn.

2 The control valve vibrates when it is close to the fully closed position. The control valve is selected to be large, and it is often used under a small opening; The medium flow direction of the single-seat valve is opposite to the closing direction.

4) The action of the regulating valve is sluggish. The phenomenon of sluggishness and its causes are as follows:

1 The stem is sluggish only when acting in one direction. Diaphragm damage and leakage in pneumatic film actuator; Leakage of type "O" seal in the actuator.

2. The valve stem is dull when it reciprocates. There is sticky blockage in the valve body; PTFE filler deteriorates and hardens or graphite-asbestos filler lubricating oil drying; If the filler is added too tightly, the friction resistance increases; High frictional resistance due to the non-straight stem; Pneumatic control valves without positioners can also lead to sluggish action.

5) The leakage of the regulating valve increases. The reasons for the leak are as follows:

1 Large leakage when the valve is fully closed. The valve core is worn, the internal leakage is serious, and the valve is not adjusted and closed tightly.

2 The valve does not reach the fully closed position. The pressure difference of the medium is too large, the rigidity of the actuator is small, and the valve is not tightly closed; There is a foreign object in the valve; Bushing sintering.

6) The adjustable range of flow becomes smaller. The main reason is that the spool is corroded and smallened, resulting in an adjustable minimum flow rate.

Understand the fault phenomenon and cause of pneumatic control valve, and take measures to solve the problem.

Check the inner wall of the room: in the case of high pressure difference and corrosive medium, the inner wall of the valve and the diaphragm of the diaphragm valve are often affected and corroded by the medium through the limbs, and the pressure resistance and corrosion resistance must be checked;

Check the valve seat: due to the infiltration of medium during work, the inner surface of the thread used to fix the valve seat is susceptible to corrosion and the valve seat is relaxed;

Check the valve core: the valve core is one of the movable parts of the regulating valve, the erosion of the medium is more serious, and the parts of the valve core should be carefully checked whether they are corroded and worn during maintenance, especially in the case of high pressure difference, the wear of the valve core is more serious due to cavitation. Severely damaged spools should be replaced; Check the seal packing:

Check whether the packing asbestos rope is dry, if PTFE filler is used, pay attention to check whether it is aging and whether its mating surface is damaged;

Check whether the rubber film in the actuator is aging and whether there is cracking.

When the control valve is filled with graphite-asbestos, lubricating oil should be added to the packing once in about three months to ensure that the control valve is flexible and easy to use. If it is found that the packing pressure cap is very low, the packing should be supplemented, and if the PTFE packing is found to be hardened, it should be replaced in time; Attention should be paid to the operation of the regulating valve during the patrol inspection, and whether the valve position indicator and the output of the regulator are consistent; For the regulating valve with a positioner, the air source should be checked frequently, and the problem should be dealt with in time; The hygiene of the control valve and the integrity of the components should be maintained at all times.

The pneumatic single-seat control valve works accurately and normally, which is very important to ensure the normal operation and safe production of the process device. Therefore, it is necessary to strengthen the maintenance of pneumatic control valves. Lifting and dismantling.