Can an idle control valve cause jerking?
Can an idle control valve cause jerking?
Yes, an idle or broken control valve can absolutely make a process plant jerk. In most circumstances, this “jerking” looks like rapid swings, oscillations, or unstable movement in the equipment downstream or the process being managed.
How an Idle Control Valve Causes Jerking
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Stiction (Static Friction): Stiction (Static Friction): Dust, rust, or hardened packing can make a valve stick when it isn’t used for a long time. When the force overcomes the friction, the valve stem tends to “stick” and then “jump,” which makes the movement jerky and the control unsteady.
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Air Supply Issues: When pneumatic actuators are not in use, they can collect moisture or develop minor leaks in tubing, boosters, or positioners. When the valve finally cycles again, the air pressure that isn’t stable causes poor modulation and sudden jumps.
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Positioner Drift: Valves that stay in one place for months may move out of place. The valve doesn’t respond smoothly when the control system ultimately asks for a change.
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Seized or Partially Jammed Trim: Internal scaling, polymer accumulation, or sludge, which is typical in idle valves, can make it hard for things to move smoothly. The valve doesn’t glide smoothly; instead, it slides in jerky steps.
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Hunting Due to Oversized Valves: When big valves are idle, they are more likely to hunt when they start moving again. Even slight modifications to the controls can generate big, unexpected swings that look like jerks.
An idle control valve can definitely cause jerking, mostly because of stiction, changes in air supply, accumulation inside the valve, or problems with the positioner. Regularly stroking the valve, calibrating it from time to time, and doing preventive maintenance can keep these problems from happening and make sure that process control stays stable.