Troubleshooting Guides · Free Tool
ESD and On Off Valve Fault Finder
Choose what the shutdown or on off valve does and get likely causes, checks and fixes for valve, actuator, solenoid and switches.
Fails to closeSlow strokeLimit switchPST fails
SymptomDoes not move on trip
Most likely causeSolenoid stuck or not de energised
First checkCheck output and solenoid exhaust
Causes in order of likelihood
| Cause | How to check | Fix |
|---|---|---|
| Solenoid stuck or not de energised | Check output and solenoid exhaust | Repair or replace solenoid |
| Exhaust port blocked (insects, ice, dirt) | Inspect vents | Clear and fit protected breathers |
| Valve seized or high friction | Manual operation test | Overhaul valve and actuator |
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Before You Start
- Work under a permit, inform the control room and put the loop in manual or bypass the trip before touching a live instrument.
- Record as found stroke times before any work.
- Check air supply pressure and solenoid power.
- Agree test method with operations; ESD valves may need the unit in a safe state.
ESD and On Off Valve Fault Finder: All Symptoms
Does not move on trip
| Likely cause | How to check | Fix |
|---|---|---|
| Solenoid stuck or not de energised | Check output and solenoid exhaust | Repair or replace solenoid |
| Exhaust port blocked (insects, ice, dirt) | Inspect vents | Clear and fit protected breathers |
| Valve seized or high friction | Manual operation test | Overhaul valve and actuator |
Stroke too slow
| Likely cause | How to check | Fix |
|---|---|---|
| Solenoid or tubing too small | Compare Cv and tubing with design | Upsize or add quick exhaust |
| Partly blocked exhaust | Inspect silencers and ports | Clean or replace |
| Increased valve friction | Stroke time trend rising | Service packing and valve |
Position feedback wrong
| Likely cause | How to check | Fix |
|---|---|---|
| Limit switch cam misaligned | Compare indicator with switch state | Adjust cams at true end positions |
| Switch or cable fault | Test switch continuity | Replace switch or repair cable |
| Valve not reaching end position | Visual check | Check actuator stops and supply |
Partial stroke test fails
| Likely cause | How to check | Fix |
|---|---|---|
| Valve sticking at start | Check breakaway pressure in test data | Service valve; review actuator margin |
| Test parameters wrong | Review PST settings | Correct settings |
| Positioner or PST device fault | Device diagnostics | Repair device |
Passes when closed
| Likely cause | How to check | Fix |
|---|---|---|
| Seat damage | Leak test | Repair seats |
| Not fully closed | Check travel and stops | Adjust stops |
| Debris on seat | Inspect | Clean; check strainers |
Key insight: a stroke time that creeps up between tests is the earliest warning that a shutdown valve may not close when demanded.
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Frequently Asked Questions
What is a typical ESD stroke time?
It is set by the process safety time; there is no single typical value.
Why do exhaust ports block?
Insects, ice and dirt; protected breathers prevent it.
Does PST replace a full stroke test?
No, it complements full proof tests.
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