Pneumatic film regulating valve under what circumstances must use the valve positioner

Pneumatic film regulating valve under what circumstances must use the valve positioner

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Pneumatic film regulating valve inspection method:
Check the leakage of sealing packing box and other joints
The temperature of the water at room temperature is 1.1 times the nominal pressure of the regulating valve or 1.5 times the maximum operating pressure, according to the direction of opening the spool into one end of the regulating valve, the other end is closed. Hold the pressure for 10 minutes while the stem moves 1-3 times per minute. There should be no leakage in the connection of sealing packing box and other components.
2 Check for leaks during shutdown
① Leakage inspection of water injection method
For the two seat regulating valve can be used in general simple water injection method to check the leakage situation. Input signal pressure into the film gas chamber to close the regulating valve (input 1.2kg/cm2 signal pressure into the gas close valve, and the gas open valve signal pressure is zero). The inlet of the regulating valve is injected at room temperature water, in the case of no pressure at the other end should be no drip phenomenon.
② Check the leakage of water pressure
This method can be used for accident cut off or close tight single seat regulating valve, Angle regulating valve and diaphragm valve.
Input signal pressure to the membrane chamber to close the regulator. The water at room temperature is passed into one end of the regulating valve at a constant pressure of 10kg/cm2 in the direction of opening the spool. The leakage quantity measured at the other end with a stopwatch and measuring cup should not exceed the allowable value.
Pneumatic film regulating valve under what circumstances must use the valve positioner
1. When the output signal of the electric regulator is used to operate the pneumatic actuator in the compound regulation occasion, it is required to have positioning function. When the output signal of the electric regulator is used to operate the pneumatic actuator, it is required to have positioning function at the same time, it can use the electric-gas positioner

2, two position action into proportional action adjustment occasions no spring or piston actuator is two-position action, when required to have proportional adjustment, no spring or piston actuator is two-position action, when required to have proportional adjustment, must use the valve positioner. A valve positioner must be used.

3, for the occasion of high pressure difference between the two ends of the valve 10kgf/cm medium on the spool unbalance force is larger, when △P > 10kgf/cm2, the medium on the spool unbalance force is larger, by improving the air source pressure of the positioner to reach the actuator output force, to overcome the medium on the spool unbalance force. The air source pressure reaches the output force of the actuator to overcome the unbalanced force of the medium on the spool.

4, for high pressure media in this case in order to prevent the penetration of the medium, the packing is very tight, the friction is larger, in this case in order to prevent the penetration of the medium, the packing is very tight, the friction is larger, at the same time, the uneven force of the medium on the spool is also larger, the requirement of positioning device to overcome. The unbalanced force of the mass on the spool is also large, which requires a locator to overcome.


Post time: Nov-25-2022

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