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Routine maintenance of pneumatic control valve

Update:14-12-2018
Summary:

When the regulating valve is made of graphite-asbestos, […]

When the regulating valve is made of graphite-asbestos, the lubricating oil should be added to the packing for about three months to ensure the flexibility of the regulating valve. If it is found that the packing pressure cap is pressed very low, the filler should be replenished. If the polytetrafluoroethylene dry packing is found to be hardened, it should be replaced in time; the operation of the regulating valve should be paid attention during the inspection, and the valve position indicator and regulator should be checked. Whether the output is consistent; check the gas source for the regulating valve with the positioner, and find the problem in time; always keep the health of the regulating valve and the complete and easy use of the components.

The regulating valve does not work. The symptoms and causes are as follows:

1. No signal, no gas source.

a.The gas source is not open,

b.Because the gas source water freezes in winter, the air duct is blocked or the filter and the pressure reducing valve are blocked,

c.compressor failure;

d.gas source manifold leakage.

2. There is a gas source, no signal.

a.regulator failure,

b.signal tube leakage;

c.positioner bellows leakage;

d.regulation mesh diaphragm damage.

3. The positioner has no air supply.

a.filter blocked;

b.pressure relief valve failure

c.pipe leakage or blockage.

4. The positioner has a gas source and no output.

The orifice of the positioner is blocked.

5. There is signal, no action.

a.valve core is off,

b.valve core is stuck with the society or with the valve seat;

c.valve stem is bent or broken;

d.valve seat valve core is frozen or coke block dirt;

e.actuator spring is rusted due to long-term use.

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