Fifteen of the most common field faults of valve electric actuators, with causes and remedies, for quick reference by maintenance staff.
| Common actuator faults and remedies | ||
|---|---|---|
| Fault | Cause | Remedy |
| 1. Motor will not start | No supply; low voltage; thermal relay (KH) tripped; T.SW tripped; valve operating torque too high. | Check supply; check voltage; wait for KH to recover; 1. turn T.CW towards higher torque; 2. force-adjust; check the valve. |
| 2. Motor stops during open/close travel | Overload tripping the torque switch; thermal relay tripped; poor valve condition, high load. | Raise torque setting if margin remains; adjust thermal relay; 1. check and restore the valve; 2. if possible, exercise the valve electrically periodically. |
| 3. Gear limit switch will not stop motor | Motor reversed; switch badly adjusted; adjusting screw not returned after setting; control supply switch faulty; limit-switch gear damaged. | Rewire with valve at mid-position; readjust; return the adjusting screw; find and clear the fault; inspect/replace gear. |
| 4. T.SW / GL.SW tripped but motor keeps running | Motor reversed; earth fault. | Rewire with valve at mid-position; measure earthing resistance. |
| 5. Open/close indicator lamps not lit | Torque switch tripped before the valve reached its position. | Adjust the torque switch. |
| 6. Remote opening indication frozen | Potentiometer drive gear loose, potentiometer shaft not turning; poor supply; potentiometer failed. | Tighten screws; check supply; replace potentiometer. |
| 7. Motor runs but valve does not move | Hand/electric changeover faulty; lock nut loose. | Strip, inspect and repair; tighten nut. |
| 8. Handwheel will not turn | Clutch dogs butting, not engaged. | Rotate slightly to offset the dogs. |
| 9. Stem vibrates at start | Stem nut loose or badly tightened. | Remove stem cover or pipe plug and tighten the lock nut. |
| 10. Poor insulation | Rain ingress (poor cable-entry sealing). | Repair seals; dry components and motor; seal the cable entry. |
| 11. Oil leak | Seal damaged; high ambient pressure inside housing. | Repair seals; loosen a non-critical screw (preferably the plug) to vent. |
| 12. Local control OK, remote dead | PLC input signal problem; EPC output problem; EPC burned. | Check supply; check PLC input; check EPC output; replace EPC. |
| 13. Local OK, remote position display lost | Relay failed; connector fallen out; VOT transmitter burned. | Check supply; check VOT output; check wiring; replace VOT. |
| 14. No open/close action from the actuator | Torque switch failed; travel switch failed. | Overhaul or replace torque/travel switches. |
| 15. No hand/electric changeover | Overload tripped torque protection; lock hooks/gears damaged; disengaging lever fallen off the worm gear. | Disconnect actuator from valve to reset torque; replace lock hooks/gears; refit lever. |
