The Hidden Risk in Your Valve Inventory
Valve actuator gearboxes are among the most neglected items in plant maintenance programmes. Because they rarely fail spectacularly — they usually seize gradually over months or years — they are easy to overlook until a critical valve cannot be operated during an emergency or shutdown.
Common Gearbox Failure Modes
- Grease degradation: Factory-filled grease ages and loses lubricity, particularly in high-temperature environments. Hardened grease becomes an abrasive rather than a lubricant.
- Moisture ingress: Deteriorated seals allow water entry, leading to internal corrosion of gear teeth and shaft bearings.
- Gear tooth wear: Operating under repeated high torque loads accelerates gear tooth wear.
- Seal failure: Stem and shaft seals harden over time, particularly in outdoor installations exposed to UV and temperature cycling.
- Indicator misalignment: Mechanical open/close indicators drift out of calibration.
Early Warning Signs
Catching gearbox deterioration early avoids emergency replacement. Indicators to watch for include increasing operating torque, audible grinding or clicking during operation, visible corrosion or seal damage on external inspection, grease discolouration or extrusion from seals, and indicator position errors.
Recommended Service Intervals
For standard industrial gearboxes in moderate environments, a 3–5 year preventive maintenance interval is typical. For harsh environments (coastal, high temperature, chemical exposure), 2-year intervals are recommended. Each service should include full disassembly, cleaning, bearing inspection, gear tooth inspection, re-packing with fresh grease, seal replacement, and indicator re-calibration.
Valve Exercising Programme
All valves — particularly those that remain in one position for extended periods — should be included in a regular exercising programme. Moving a valve through at least a partial stroke every 6–12 months prevents internal components from seizing. Our mobile workshops are equipped to perform valve exercising programmes during planned shutdowns.