Pressure Measurement Failures – Root Cause Analysis
This guide follows mechanical-first troubleshooting logic. In most plants, pressure problems originate from impulse lines, manifolds, or installation errors — not transmitter electronics.
Common Pressure Problems & Root Causes
| Symptom | Likely Cause | Field Check | Corrective Action |
|---|---|---|---|
| Zero Shift |
Condensate imbalance Equalizing valve open Sensor drift after shutdown |
Equalize manifold Drain impulse legs Verify 4 mA output |
Balance impulse legs Close equalizing valve Perform zero trim if required |
| Unstable Reading |
Air ingress Loose fittings Process flashing Vibration |
Soap test fittings Inspect slope Observe trend pattern |
Tighten connections Re-route impulse lines Add damping or snubber |
| Slow Response |
Plugged impulse line Wax/dust buildup Long impulse routing |
Crack impulse slowly Compare with local gauge |
Flush impulse line Shorten routing if possible |
| No Output (4 mA Flat) |
Blocked impulse line Heat tracing failure Loop power failure |
Check 24V supply Inspect fuses Verify manifold isolation |
Restore power Clear blockage Repair heating |
| High Reading |
Low side blocked Equalizing valve closed during calibration Incorrect LRV |
Crack LP impulse Verify calibration range |
Clear LP blockage Correct scaling |
| Low Reading |
High side blocked Leak on HP impulse Incorrect URV |
Crack HP impulse Inspect fittings |
Clear HP blockage Repair leakage Correct scaling |
Mechanical-First Rule
- 80% issues → impulse lines
- 10% → manifold handling error
- 5% → wiring or loop issue
- 5% → actual transmitter failure
Replace transmitters only after mechanical causes are eliminated.