When to Replace a Valve: Service Life and Inspection Triggers
Quick Answer
Replace a valve when inspection shows it can no longer meet its function safely: external leakage at the stem or body, seat leakage beyond the specified leakage class, failure to operate or stroke, or wall thinning past the allowable limit. API 574 guides valve inspection practice and API 570 covers the piping system around it. A risk-based program uses those findings to set the next interval.
What Limits Valve Life
- Seat and disc wear: leads to internal leakage and loss of isolation.
- Stem and packing wear: causes external (fugitive) leakage.
- Body and bonnet corrosion: reduces pressure-retaining wall thickness.
- Actuator and linkage: fail to open, close or modulate.
Inspection Triggers
| Finding | Typical action |
|---|---|
| External leak at stem or body | Repair packing or replace valve |
| Seat leak beyond leakage class | Lap, repair or replace |
| Actuator fails to stroke | Overhaul or replace actuator |
| Wall loss past API 574/570 limit | Replace |
Codes and Guidance
API 574 gives inspection intervals and methods for valves in refinery service. API 570 sets the inspection of piping systems, which includes valves in the line. Wall-thickness measurements and leak tests feed the decision.
Risk-Based Inspection
RBI ranks valves by the consequence of failure (fluid hazard, line criticality) and the likelihood (history, environment). High-risk valves are inspected more often; low-risk valves can run longer. This avoids replacing every valve on a fixed schedule.
Related Reading
For failure modes and fixes, see the valve troubleshooting guide. For material limits in corrosive service, see the material compatibility guide.
Frequently Asked Questions
When should a valve be replaced?
Replace it when inspection finds external leakage, seat leakage beyond the allowed class, actuation failure, or wall loss past the code limit.
What do API 574 and API 570 cover?
API 574 covers inspection of valves; API 570 covers inspection of the piping systems that valves are part of. Together they guide replacement decisions.
Is valve replacement based on a fixed time?
Not ideally. Service life is set by inspection findings; a risk-based program aligns intervals with failure consequence and likelihood.
How does seat leakage class affect replacement?
If seat leakage exceeds the specified leakage class (for example API 598 rates), the valve no longer isolates and should be repaired or replaced.