Primary Output
Continuous Wobbe Index / CV for burner control and fuel blending.
Top Field Causes
Moisture, liquid carryover, pressure hunting.
Fix Order
Sampling → Pressure → Stability → Calibration → DCS
Technician Rule
If unstable — do not calibrate yet.
Technician priority: Incorrect Wobbe values are almost always caused by
sample conditioning or pressure instability.
Fix these before calibration.
Working Principle (Technician View)
Wobbe Index represents the energy flow through a burner or orifice at a given pressure. It allows combustion systems to maintain stable heat input despite fuel composition changes.
- Accuracy depends on: dry sample, stable pressure, clean conditioning
- Instability usually means: moisture, liquid, or regulator hunting
- Electronics failures: rare compared to sample-related issues
Main Components (Field Focus)
- Sampling system – probe, tubing, isolation valves
- Conditioning – filters, coalescers, drains, heat tracing
- Pressure / flow control – regulators, restrictors
- Measurement module – sensing and calculation
- Electronics & comms – controller, I/O, Modbus/OPC
Calibration Procedure (Field Standard)
- Confirm stable sample and pressure (no active alarms)
- Verify filters, drains, and regulator stability
- Apply reference / zero condition and allow stabilization
- Apply span / reference point and verify response
- Return to process and confirm stable trend
- Verify DCS scaling and quality flags
Calibrating an unstable analyzer will temporarily “fix” the value
and guarantee another failure later.
Major Troubleshooting (Fast Isolation)
- Fluctuating Wobbe → pressure hunting, wet sample
- Wrong vs lab → stabilize first, then check DCS scaling
- Sudden jump → liquid carryover or process upset
- Calibration won’t hold → unstable sample or leaks
- No DCS update → mapping, scaling, protocol mismatch
- Slow drift → moisture ingress, contamination, temperature