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HomeNewsAnalysis of common problems of pneumatic diaphragm valve

Analysis of common problems of pneumatic diaphragm valve

2020-10-02
Analysis of common problems of pneumatic Diaphragm Valve



1. Air source system failure



1. Instrument air line is blocked. As the Ball Valve has throttling effect at the end of the instrument branch air line, the dirt in the air line is easy to accumulate and block. As a result, the instrument air pressure is too low, the Control Valve can not be fully opened and closed, and even the control valve does not act.



2. Air filter pressure reducing valve failure. The air filter pressure reducing valve has been used for a long time with too much stolen goods, and the air leakage of the pressure reducing valve. The set output pressure of the pressure reducing valve is too low, so that the output air pressure of the instrument is less than the specified pressure. As a result, the regulating valve acts slowly and can not be fully opened or closed or even does not act.



3. Copper pipe connection failure. Due to the aging and air leakage of the copper pipe, the connection of the joint is loose or the copper pipe is blocked by dirt, so that the air pressure of the instrument signal is low, so that the control valve does not act and can not be fully opened and closed, and the valve position in manual state is unstable, resulting in regulation oscillation.



4. Instrument air system failure. The air compressor station is abnormal, the purification air tank of the device is abnormal, the water cut is not timely, the air line is frozen, the instrument air line is leaking or blocked by stolen goods, resulting in the instrument air pressure is too low or even no wind. 5. The valve of instrument air branch line is not opened, which causes the regulating valve not to act. It often occurs during the period of overhaul and start-up after revamping.



2. Power system failure



1. Power line terminal loose, short circuit, fall off, polarity reversal fault. Due to the field vibration, loose wiring or too much dust caused poor contact, so that the signal from the control room to the site is sometimes absent, resulting in the chaotic action of the control valve, resulting in regulation oscillation. Due to wiring error, equipment water or moisture and other reasons, the power line wiring is short circuited, so that the signal received by the control valve is lower than that of the regulator, resulting in the control valve can not be fully opened and closed. The control valve does not work when it falls off and the polarity is reversed. Abnormal polarity connection occurs in the installation of new meters, new wiring, overhaul of the device, etc.



2. The middle connector or middle injury of power line is faulty. Due to the vibration of the environment and the pulling of the external force, the failure of the insulating tape, the degradation of the insulation performance and the high temperature baking of the joint, the power line connector is loose or seems to be broken, the short circuit between the power lines or to the ground, and the connector or power line is broken. As a result, the action of the control valve is not continuous, and it can not be fully opened or closed. In the process of maintenance, the middle connector of power line is connected reversely, which causes the regulating valve not to act.



3. The control valve is not controlled by the regulator. During the overhaul and start-up of the plant, the wrong connection of the power line or the wrong configuration in the control room caused the control valve not to be controlled by the regulator.



3. Electrical converter failure



1. Zero point and measuring range are not accurate. The zero point and range of the output signal of the converter are inaccurate due to inaccurate installation and debugging, site vibration and temperature change. As a result, the control valve can not be fully opened and closed, and the leakage is large and limited. In the field adjustment of the converter, it is necessary to ensure the accuracy of the small signal meter of the converter. Generally, the small signal meter should be maintained.



2. The orifice is blocked. The instrument wind dirt blocks the throttle hole. As a result, the control valve does not act.



3. The output is not linear. The output of the converter is not linear due to the aging of coils and components in the converter or the influence of field vibration and ambient temperature. As a result, the required value can not be reached in the process of zero point and range adjustment. The action of the regulating valve is not linear and can not be fully opened and closed.





Common problems in using diaphragm valve diaphragm

After the diaphragm valve diaphragm is used for a long time, the rubber pad on the valve core of the pulse valve is easy to be damaged. The appearance is that the pulse valve deflates to the nozzle for a long time, and the treatment method is to replace the rubber pad.



As the diaphragm valve diaphragm air intake is not clean, resulting in dirt accumulation at the valve core, resulting in the appearance of long-term air intake at the nozzle or pulse valve does not act after power on, the treatment method is to clean the valve core. The spring on the valve core of submerged electromagnetic pulse valve is easy to be damaged. The appearance is that the pulse valve deflates to the nozzle for a long time, and the treatment method is to replace the spring.



After the diaphragm valve diaphragm works for a long time, the diaphragm is easy to fatigue and oxidize. The appearance is that the pressure relief port deflates for a long time, and the diaphragm valve diaphragm does not work. The treatment method is to replace the diaphragm. If the air intake of diaphragm valve diaphragm is not clean, it is easy to cause the throttle orifice to be blocked. The surface is that the pulse valve deflates to the nozzle for a long time. The treatment method is to clean the throttle orifice. If the orifice is damaged or missing, the throttling orifice will lose its interception effect, resulting in abnormal pressure relief. The appearance is that the pulse valve will act after power on, and the pressure relief port will be deflated, but the pulse valve will not be injected. The treatment method is to replace the throttle orifice.
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