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100 Problems & Solutions For Pneumatic Globe Type Control Valves

Sep 11, 2020

  • 1. What is the reason that makes control valve stem moves slowly or does not action?

    • Check the diaphragm, whether the rolling diaphragm is aged or cracked, causing air leakage.


2. What is the reason that cause air to close control valve can not close tight? And how to solve this problem?

  • Check whether the output force of the actuator is too small. 

  • The effective output pressure PF can be adjusted to increase the output force. For air to close control valves, the adjusting element is left-turned (loose), that is means p0 ~ pL moves forward, but please attention if the full stroke/travel is changed.


3. What should you do if the control valve does not close due to full stroke deviation?

  • The full stroke/travel of the control valve is not enough to affect the flow rate or the full stroke to exceed the positive deviation, which affects the valve to Shut tight.

  • Loosen the nut, turn the valve stem outward or extend it inward so that the full stroke deviation does not exceed the allowable value, and then tighten the nut.

4. What could be the reason for the oscillation when the valve opening is small? How to deal with it?

  • A small opening will oscillations, and the stability of the control valve may be weak.

  • Check whether the flow direction is reversed and the flow to closed. If the valve should be installed according to the flow to open type, check whether the valve sizing diameter is too large, working at a small opening, and whether Pr is selected too small.

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