Analysis of common problems of pneumatic diaphragm valve

Common malfunctions

First, the gas source system is faulty

1. The instrument wind line is blocked. Since the ball valve has a throttling effect at the end of the instrument branch wind line, the dirt in the wind line is easy to accumulate and block here. As a result, the instrument wind pressure is too low, the regulating valve cannot be fully opened and closed, and even the regulating valve does not operate.

2. The air filter pressure reducing valve is faulty. The air filter pressure reducing valve uses too much waste for a long time, the pressure reducing valve leaks air, and the pressure reducing valve sets the output pressure to the bottom, so that the output instrument wind pressure is less than the specified pressure. As a result, the regulating valve is slow to operate, and it cannot be fully opened or even closed.

3. The copper tube connection is faulty. The copper tube is aging and leaking, the joint connection is loose or the material is blocked. The wind pressure of the instrument signal is low, so that the regulating valve does not operate, and the valve cannot be fully opened. The manual valve position is unstable and the adjustment oscillation is generated.

4. The instrument wind system is faulty. The air compressor station is abnormal, the device purifies the wind tank abnormally, the water cut is not timely, the wind line is frozen, the instrument wind line is leaking or blocked by the stolen goods, causing the device instrument to have too low or no wind pressure. 5. The instrument wind branch line valve is not open, causing the regulating valve not to operate. Often occurs during overhaul of the unit and during driving.

Second, the power system failure

1. The power cable terminal is loose, short circuited, disconnected, and the polarity is reversed. Due to on-site vibration, the wiring is not tight, causing loose wiring or too much dust, causing poor contact, and sometimes the signal from the control room to the scene is not present, causing the regulating valve to operate in disorder and causing adjustment oscillation. Due to wiring errors, the equipment is short-circuited due to water ingress or dampness, so that the signal received by the regulating valve is lower than the signal of the regulator, causing the regulating valve not to fully open and close. The dropout and polarity reverse adjustment valves do not operate. Polarity abnormalities occur when installing new meters, rewiring, and overhauling devices.

2. The intermediate connector of the power cord or the middle of the injury is faulty. The power cord is loosened or disconnected by the vibration of the environment, the pulling of external force, the insulation performance of the insulating tape, and the high temperature baking of the joint water. The power cable is short-circuited or short-circuited to the ground, and the wiring head or The power cord is broken. As a result, the regulating valve does not move continuously, and cannot be fully opened and closed. During the maintenance process, the middle of the power cord is reversed, causing the regulating valve to not operate.

3. The regulating valve is not controlled by the regulator. In the overhaul of the device, the power line is connected incorrectly during the driving process or the control room configuration is wrong, and the regulating valve is not controlled by the regulator.

Third, the electrical converter failure

1, zero, the range is not allowed. The zero point and range of the converter output signal are not accurate due to inaccurate installation or commissioning or on-site vibration and temperature changes. As a result, the regulating valve can not be fully opened and closed, the leakage amount is large, and the limit is limited. In the field calibration of the converter, it should first ensure that the converter signal small table indication is accurate. The signal small table should be maintained in general.

2. The orifice is blocked. The instrument wind smashes the throttle hole. Causes the regulator to not act.

3. The output is not linear. Due to the aging of the coils and components in the converter or the influence of the on-site vibration and ambient temperature, the output of the converter is not linear, so that the required value cannot be achieved during the zero-point and span adjustment, and the regulating valve does not operate linearly. Fully open and closed.