5 Common Control Valve Issues: Diagnostics and Solutions

Control valves are workhorses of industrial process control, and when something's off, the effects ripple through your entire system. Here are five common issues worth having on your radar.

Deadband (Hysteresis): Deadband happens when there's a lag between the control signal and the valve's actual position, often caused by backlash, excessive friction, or loose actuator connections. It can trigger oscillations in PI or PID loops and hurt system stability. Step tests or diagnostic software can identify it, and solutions range from replacing worn components to implementing deadband compensation.

Stiction (Static Friction): Stiction causes a valve to hold its position despite a changing signal, then suddenly break free and overshoot, leading to erratic flow control and process variability. Over- tightened stem seals, contamination, and undersized actuators are frequent causes. Regular lubrication, seal replacement, and proper actuator sizing are the usual fixes.

Positioner Overshoot: When a positioner is tuned too aggressively or begins to fail, the valve repeatedly overshoots its target, causing unstable control and accelerated wear. Retuning to manufacturer specs or upgrading to a smart positioner typically resolves it.

Oversized Control Valves: A valve that's too large for its application reduces rangeability, causes poor control resolution at low flow rates, and amplifies other positioning problems. If your valve rarely operates above 50–60% open, it may be oversized. Replacing it, installing a reduced trim kit, or using split-range control are all options worth considering.

Nonlinearity: Nonlinear flow characteristics can make a loop behave differently across its operating range, sluggish in one spot and unstable in another. Valve stroking tests help identify the issue, and linearization in your DCS or PLC, or adaptive tuning, can compensate. If you're seeing signs of any of these issues in your system, Omni can help diagnose

the problem and get your control valves back in spec. Reach out to our team to learn more.