Steam Control Valve Maintenance Analysis

Inspection site during inspection

Check the inner wall of the chamber: In the occasion of high pressure difference and corrosive medium, the diaphragm of the inner wall of the valve body and the diaphragm valve is often subjected to the impact and corrosion of the medium, and the stress resistance and corrosion resistance must be checked;

Check the valve seat: Because the medium penetrates during work, the inner surface of the thread used to fix the valve seat is susceptible to corrosion and causes the valve seat to loosen;

Checking the valve plug: The valve plug is one of the movable parts of the regulating valve. It is seriously eroded by the medium. When checking, it is necessary to check whether the various parts of the valve plug are corroded and worn. Especially in the case of high pressure difference, the valve plug The cavitation caused by cavitation is even more serious. Severely damaged valve plug should be replaced; check the seal packing: check the packing asbestos rope is dry, such as the use of PTFE packing, should pay attention to check whether the aging and its mating surface is damaged;

Check whether the rubber film in the actuator is aged and cracked.

Daily maintenance of steam regulating valve

When the regulating valve adopts graphite-asbestos as the filling material, a lubricant should be added to the packing for about three months to ensure that the regulating valve is flexible and easy to use. If the filler pressure cap is found to be very low, fillers should be added. If it is found that the polytetrafluoroethylene dry filler is hardened, it should be replaced in time; attention should be paid to the operation of the regulating valve in the inspection tour, check the valve position indicator and regulator Whether the output is consistent or not; for the regulating valve with positioner, the gas source should be checked frequently, and the problem should be solved in time; the health of the regulating valve and the completeness and ease of use of the components should be maintained.

Steam regulator valve common faults and their causes

(a) The regulating valve does not move. The symptoms and causes are as follows:

1. No signal, no air source. 1 The air source is not open, 2 Because the air source contains water in the winter, freezing, leading to blockage of the air duct or filter, pressure relief valve plug failure, 3 compressor failure; 4 gas source mains leakage.

2. There is a source of gas, no signal. 1 regulator failure, 2 signal tube leakage; 3 positioner bellows leak; 4 adjust the mesh diaphragm damage.

3. Locator without air source. 1 Filter clogged; 2 Pressure reducing valve fault I3 Pipe leaking or blocked.

4. The positioner has a gas source and no output. The retainer throttle block.

5. There is a signal, no action. 1 spool off, 2 spool and society or with the valve seat stuck; 3 stem bent or broken; 4 seated spool frozen or coke block dirt; 5 actuator spring due to long-term use without rusting.

(b) The operation of the steam regulating valve is not stable. The symptoms and causes are as follows:

1. The source pressure is not stable. 1 compressor capacity is too small; 2 pressure relief valve failure.

2. The signal pressure is not stable. 1 The time constant of the control system (T=RC) is inappropriate; 2 the regulator output is not stable.

3. The source pressure is stable and the signal pressure is also stable, but the operation of the regulating valve is still unstable. 1 The ball valve of the amplifier in the positioner is loosely shut off by the dirt. When the air consumption increases, the output oscillation will occur. 2 The nozzle baffle of the amplifier in the positioner is not parallel, and the baffle cannot cover the nozzle. 3 Output pipe , Line leakage; 4 The rigidity of the actuator is too small; 5 The frictional resistance in the valve stem movement is large, and there is a blocking phenomenon with the contact parts.