Valve Troubleshooting: Common Failures, Causes & Maintenance
Most Valve Failures Are Preventable
A structured troubleshooting routine cuts downtime. Start from the symptom, confirm the failure mode, then trace to root cause — rarely is it the actuator alone.
Symptom-to-Cause Table
| Symptom | Likely Cause | Corrective Action |
|---|---|---|
| External leakage at bonnet | Worn packing | Retighten or replace packing |
| Seat leakage (won't shut) | Damaged/seated debris | Lap seat or clean line |
| Hard to operate | Packing too tight / stem galling | Adjust packing, lube stem |
| Actuator won't stroke | Air/power loss, signal fault | Check supply, positioner |
| Cavitation noise | Excess ΔP across trim | Resize or add trim stage |
| Vibration | Undersized or oversized Cv | Re-size per Cv guide |
External Leakage at the Packing
Packing leaks are the most common external leak. Do not over-tighten — that increases stem friction and wear. Adjust to a slight weep, then replace packing at the next outage.
Seat Leakage
A valve that will not shut may have debris on the seat or a scored seat. For soft-seated valves, particle damage is permanent; for metal-seated, lapping can restore. Confirm the leakage class expected.
Cavitation and Noise
Cavitation sounds like gravel and destroys trim. It occurs when the pressure drop exceeds the critical value. Re-size using the Cv guide and select cavitation-resistant trim.
Preventive Maintenance
- Lubricate stems on a schedule.
- Verify actuator torque margin.
- Inspect trim during outages.
- Confirm material still matches the fluid (see material guide).
When to Replace vs Repair
Frequent recurrence after repair signals wrong valve type or material for the service. Re-evaluate the choice with the selection guide before another rebuild.
Maintenance intervals and failure modes by product are tracked across valve brands in the ValveSpecs Pro database.
Frequently Asked Questions
Why is my valve leaking at the stem?
Stem leakage is usually worn or over-tightened packing. Adjust to a slight weep; replace packing at the next planned outage rather than over-tightening.
What causes cavitation noise in a valve?
Cavitation happens when the pressure drop across the trim exceeds the critical value, forming and collapsing vapor bubbles. Re-size the valve or use cavitation-resistant trim.
Why won't my valve shut off completely?
Most often debris on the seat or a damaged seat. Clean the line or lap/repair the seat; for soft seats, particle damage may require replacement.
How often should valves be maintained?
On a planned schedule: lubricate stems, verify actuator torque, and inspect trim during outages. Frequency depends on cycle count and fluid aggressiveness.
Where do I compare failure modes by product?
The ValveSpecs Pro database records maintenance-relevant attributes across 90-plus brands to support root-cause analysis.