Ganga Thermal Power Case: Temperature Transmitter for Coal-Fired Boiler Main Steam and Flue Gas Monitoring
Published On: August 27, 2026
1. Client Profile
Ganga Thermal Power Pvt. Ltd. operates a 2 x 300 MW coal-fired power station in Madhya Pradesh, India. The plant's instrumentation team manages more than 600 boiler temperature points, and main steam temperature deviation during load ramping was identified as a recurring cause of reduced cycle efficiency and tube-life risk.
2. Application Background
Boiler steam temperature is one of the most safety-critical measurements in a coal-fired power plant. Main steam and reheat steam temperatures are controlled within tight limits: too low reduces cycle efficiency, while too high risks tube creep failure. Flue gas temperatures support combustion optimization and air preheater protection. This case explains the temperature transmitter configuration for a typical coal-fired boiler and the engineering details buyers must check.
3. Real Operating Conditions
| Measurement Point | Typical Temperature | Pressure / Environment |
|---|---|---|
| Main steam | 540-570°C | Up to 25 MPa, high-velocity steam |
| Reheat steam | 540-570°C | Approx. 4-6 MPa steam |
| Flue gas (economizer outlet) | 300-400°C | Fly-ash laden, erosive |
| Feedwater | 200-300°C | High-pressure water |
| Bearing and auxiliary | 60-100°C | Vibration, oil mist |
4. Customer Pain Points
- Thermowell failure under flow-induced vibration can cause steam leaks and forced outages; ASME PTC 19.3 compliance is often overlooked at the procurement stage.
- Erosion by fly ash shortens flue gas sensor life and causes reading drift.
- Electromagnetic interference from variable-frequency drives and high-voltage switchgear corrupts temperature signals.
- Slow response delays detection of steam temperature excursions during load ramps.
5. Engineering Selection
- Main and reheat steam: armored K-type thermocouple or Class A Pt100 in a heavy-duty thermowell designed and checked per ASME PTC 19.3 (natural frequency versus vortex shedding), with alloy steel or 316L thermowell matched to the pressure rating.
- Flue gas: thermocouple with an abrasion-resistant protection tube (ceramic or tungsten-carbide coated) and corrosion-resistant sheath for the measured zone.
- Bearing temperature: small Pt100 elements with vibration-resistant mounting.
- Intelligent integrated transmitter (QW-SLS65) with digital communication and self-diagnosis; QW-SLS67 with on-site display where field checking is required.
6. Recommended Qinwei Instruments for This Application
| Model | Description | Applied At |
|---|---|---|
| QW-SLS71 | Self-diagnosis intelligent transmitter, IP66/IP67 with alarm | Main and reheat steam loops with continuous health monitoring |
| QW-SLS62 | IP60 armored thermocouple, corrosion-resistant sheathed | Flue gas points with abrasion-resistant protection tube |
| QW-SLS65 | Intelligent integrated transmitter, 4-20 mA with digital communication | Feedwater and auxiliary temperature loops |
| QW-SLS63 | Class A Pt100 RTD per IEC 60751 | Bearing and auxiliary temperature with vibration-resistant mounting |
7. Installation Logic
- Install steam thermowells in pipe runs with adequate straight length upstream and orient the tip into the flow to the pipe centerline.
- Verify the thermowell natural frequency against expected vortex shedding to avoid resonance, following the ASME PTC 19.3 methodology.
- Use shielded twisted-pair cable, separate conduit from power cabling, and single-point grounding to suppress electromagnetic interference.
- For flue gas points, mount with a slight downward angle so fly ash does not accumulate on the tip, and schedule cleaning during outages.
- Use redundant sensors at critical points to allow comparison and fail-safe operation.
8. Application Results
- Reliable steam temperature measurement supports safe load ramping and reduces the risk of forced outages caused by thermowell failure.
- Accurate flue gas readings improve combustion and heat-rate optimization and protect the air preheater.
- EMI-resistant installation eliminates nuisance signal fluctuations that previously caused control hunting.
9. Why Choose Qinwei Instruments
Xi'an Qinwei Instrument Factory (brand QINWEIYB) is a manufacturer established in 2010 with 500-800 employees and 50%-60% export share. For power plants, Qinwei offers self-diagnosis transmitters with IP66/IP67 enclosures, EMI-immune 4-20 mA loops, and engineering support for ASME PTC 19.3 thermowell vibration checks. Every loop is factory-calibrated with traceable certificates, and with MOQ from 1 set and 5-8 working days delivery, plants can stock critical spares without tying up budget.
10. Purchase Decision Guide
Specify: thermowell material and pressure-temperature rating, a PTC 19.3 vibration calculation report, response time, sensor redundancy (dual elements), output and communication protocol, EMI immunity, and full material and calibration documentation. Ask the supplier for a documented thermowell design basis before ordering.
