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Pneumatic valve working principle and failure analysis


2023-12-22 09:19

1 The working principle of pneumatic valve
The so-called pneumatic valve, specifically refers to the cylinder as an actuator, compressed air as a power source to realize the drive of the valve, in order to achieve the switch to regulate. When the regulating pipeline receives the control signal issued by the automation control system, it will regulate the temperature, pressure, flow and other relevant parameters. In general, the characteristics of pneumatic valves are reliable, fast response and simple control. In the specific operation of the process, will adjust the gas chamber input 0.02-0.10MPa signal pressure, the film will appear thrust, in the process of thrust disk downward movement will be compressed spring, realize the valve stem, push rod and spool downward movement, to achieve the purpose of the valve adjustment.


2 pneumatic valve common faults and processing methods
Through the study and analysis of the failure state of pneumatic valves, it is understood that there may be faults such as valve jamming, valve inactivity, valve leakage and vibration, so it is necessary to formulate countermeasures according to the actual faults in order to realize the smooth operation of the system to create higher efficiency.


2.1 Pneumatic valve jamming
If the action of the valve stem is sluggish, it means that there may be viscous substances in the valve body, and the pneumatic valve jamming occurs mainly in the early stage of system operation. When encountering this situation, you should quickly open and close the valve or sub-line, in order to flush away the medium blocking the valve. At the same time, you can also use a pipe wrench to clamp the valve stem, and apply signal pressure to the valve stem to reverse the force of rotation. If the above problem still cannot be solved, then the drive power can be increased by means of repeated up and down movement. It should be noted that, due to the above operation has a strong professionalism, so in solving and dealing with this problem need to be completed with the help of professionals.


2.2 Valve does not move
For this fault, the first step is the need to determine whether the gas source pressure is normal, based on this to find the gas source failure. When the valve in the case of normal gas pressure, the need for electric / gas converter amplifier whether the output to judge. When there is no output, there are two possible situations: first, moisture in the air is compressed and placed in the ball valve of the amplifier; second, the amplifier constant throttle hole is blocked. In this case, it is necessary to clean the air source, remove debris, and unclog the constant throttle hole. If the valve is still inactive after the above treatment, it is necessary to unload the valve and perform a check.


2.3 Noisy valves
In the fluid flow through the valve, once there is a more pronounced pressure difference between the front and back of the situation, then it will trigger cavitation, cavitation is mainly based on the spool and the valve seat, which makes the fluid noise. Circulation capacity value if you choose too large, then you need to reset the regulating valve, select the value of the circulation capacity to adapt and match the regulating valve, which can be effective in reducing noise, the following noise elimination methods are introduced and analyzed specifically: (1) eliminate resonance noise method. Only in the state of valve resonance, can make the energy to overlap, and then produce a hundred decibels of noise. The performance of which there is a big difference, some vibration is strong, some vibration is weak, vibration is strong noise is not big, vibration is weak, noise is big; some are vibration and noise are very big. This noise tends to produce a monotone sound, after the elimination of resonance, the noise will also be reduced; (2) eliminate cavitation noise method. Cavitation as an important part of the hydrodynamic noise, the strength of the noise has a more prominent effect. Cavitation, bubble rupture will invariably produce high-speed impact, and then the local will breed a strong turbulence, cavitation noise is therefore generated. This noise produces a grating sound, which is very similar to the sound of gravel. Elimination of cavitation can effectively reduce the noise; (3) the use of sound-absorbing materials method. Attractive materials as a very common sound treatment method, the processing effect is very good. With the help of attractive materials to surround the source of noise, can effectively reduce the noise. As noise spreads, the attraction material will eliminate the noise in the area where it is surrounded by the attraction material. The main reason for this method, which is more commonly used in situations where the noise is not very loud, is that it costs a lot of money;