The valve is unstable

The symptoms and causes are as follows:

1. The gas source pressure is unstable. 1 The compressor capacity is too small; 2 The pressure reducing valve is faulty.

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

3. The air supply pressure is stable and the signal pressure is stable, but the action of the regulating valve is still unstable. 1 The ball valve of the amplifier in the positioner is not tightly worn by the dirt, and the output oscillation occurs when the gas consumption is particularly increased; 2 the nozzle flapper of the amplifier in the positioner is not parallel, the baffle cover cannot cover the nozzle; 3 output tube The line is leaking; 4 the rigidity of the actuator is too small; 5 the frictional resistance is large in the movement of the valve stem, and there is a blockage in the contact part.

Control valve selection

Selection of structural form: steam flow control should select single valve seat; large diameter, large flow, low pressure difference should choose butterfly valve, but the leakage is large at this time; when the medium is high pressure, high pressure regulating valve should be selected; Sewage, prevent valve blockage, optional angle control valve; optional three-way control valve for water volume or water temperature adjustment of heat exchanger.