Common faults and causes of self operated steam regulating valves
date:2023-10-23 15:25
Self operated steam regulating valve is a type of valve that uses compressed air as the power source, cylinder as the actuator, and uses electrical valve positioners, converters, solenoid valves, holding valves and other accessories to drive the valve, achieving on-off or proportional regulation. It receives control signals from industrial automation control systems to regulate various process parameters such as flow, pressure, and temperature of pipeline media.
Failure and Causes of Self operated Steam Regulating Valve
（1） The regulating valve does not operate. The fault symptoms and causes are as follows:
1. No signal or air source. ① The air source is not turned on, ② due to the water content in the air source freezing in winter, the air duct is blocked or the filter and pressure reducing valve are blocked and malfunctioning, ③ the compressor is malfunctioning; ④ The main air supply pipe is leaking.
2. There is an air source but no signal. ① Regulator malfunction, ② signal pipe leakage; ③ Positioner bellows leaking; ④ The adjusting mesh is damaged.
3. The locator has no air source. ① Filter clogged; ② Pressure reducing valve malfunction I ③ Pipeline leakage or blockage.
4. The locator has an air source but no output. The throttle hole of the locator is blocked.
5. There is a signal but no action. ① The valve core falls off, ② the valve core is stuck with the society or the valve seat; ③ The valve stem is bent or broken; ④ Frozen valve seat or burnt block dirt; ⑤ The actuator spring rusted due to long-term use.
（2） The action of the regulating valve is unstable. The fault symptoms and causes are as follows:
1. The air supply pressure is unstable. ① The compressor capacity is too small; ② Pressure reducing valve malfunction.
2. The signal pressure is unstable. ① The time constant (T=RC) of the control system is not appropriate; ② The regulator output is unstable.
3. The air supply pressure is stable, and the signal pressure is also stable, but the action of the regulating valve is still unstable. ① The ball valve of the amplifier in the locator is not tightly closed due to wear and tear from dirt, which can cause output oscillation when the air consumption increases significantly; ② The nozzle baffle of the amplifier in the locator is not parallel, and the baffle cannot cover the nozzle; ③ Air leakage in output pipes and lines; ④ The rigidity of the actuator is too small; ⑤ During the movement of the valve stem, there is a high frictional resistance and obstruction in the contact area.
