Viet Long Steel Case: Temperature Transmitter in Steel Reheating Furnace Zone Control up to 1250 Degree C
Published On: August 27, 2026
1. Client Profile
Viet Long Steel Co., Ltd. in Ba Ria-Vung Tau, Vietnam, operates a 500,000 t/y bar and wire-rod rolling line fed by a walking-beam reheating furnace. The mill's target is consistent billet discharge temperature across all zones, and frequent soaking-zone thermocouple failures were forcing unscheduled furnace interventions.
2. Application Background
Reheating furnaces bring steel billets, blooms or slabs to rolling temperature with a controlled thermal profile. Zone temperature measurement - preheating, heating and soaking - is the basis of combustion control and final product quality. This case describes the thermocouple and temperature transmitter configuration for a typical walking-beam or pusher reheating furnace, together with the selection logic buyers need.
3. Real Operating Conditions
| Furnace Zone | Typical Temperature | Environment |
|---|---|---|
| Preheating zone | 400-800°C | Combustion gas, scale dust |
| Heating zone | 800-1100°C | Oxidizing atmosphere, radiant heat |
| Soaking zone | 1100-1250°C | Highest temperature, near-flame |
Mechanical abuse during billet charging and discharging, scale fallout and thermal shock are normal operating conditions.
4. Customer Pain Points
- Thermocouples in the soaking zone burn out quickly, and replacement requires a furnace outage or hot work.
- Scale and dust build-up cause readings to drift away from the true gas temperature.
- Non-uniform zone temperature produces off-spec rolling temperatures, surface defects and higher fuel consumption.
- Conventional ceramic tubes crack from thermal shock during furnace stops and restarts.
5. Engineering Selection
- Soaking zone: R-type or S-type thermocouple (rated up to approximately 1300°C) in a high-alumina or SiC ceramic protection tube for thermal-shock and flame resistance.
- Heating and preheating zones: K-type armored thermocouple with a metal or ceramic protection tube depending on zone temperature.
- Intelligent integrated transmitter (QW-SLS65) for each zone; QW-SLS67 with local display for burner-zone field checks.
- Heavy-duty terminal heads with heat shields and high-temperature flexible cable.
6. Recommended Qinwei Instruments for This Application
| Model | Description | Applied At |
|---|---|---|
| QW-SLS61 | Durable high-temperature thermocouple, fast response | Soaking zone up to 1250°C with ceramic protection tube |
| QW-SLS60 | Anticorrosive thermal resistor, high-temperature resistant | Heating zone with metal or ceramic tube options |
| QW-SLS65 | Intelligent integrated transmitter, 4-20 mA with digital communication | Zone loop conversion with remote configuration |
| QW-SLS67 | Temperature transmitter with on-site display | Burner-zone field checks and furnace startup |
7. Installation Logic
- Install sensors through the roof or sidewall at positions that represent true zone temperature, away from direct flame impingement where possible.
- Set insertion depth so the tip sits in the active gas stream; use ceramic fiber packing to seal the opening and reduce heat loss.
- Protect terminal heads from radiant heat with shields and route cable away from hot surfaces.
- Keep calibrated spare sensors with pre-made leads so replacement during a maintenance window takes minutes rather than hours.
8. Application Results
- Stable zone temperature control improves billet temperature uniformity, reducing rolling defects and fuel consumption per ton.
- Ceramic protection tubes withstand thermal cycling, extending service life between replacements.
- Pre-made spare assemblies shorten outage time for sensor exchange.
9. Why Choose Qinwei Instruments
Xi'an Qinwei Instrument Factory (brand QINWEIYB) has specialized in industrial temperature measurement since 2010, employing 500-800 people and exporting 50%-60% of production. For reheating furnaces, Qinwei supplies R/S-type thermocouples rated to approximately 1300°C, SiC and high-alumina protection tubes, and pre-made spare assemblies with matching calibration so a failed sensor can be swapped within a maintenance window. MOQ from 1 set and 5-8 working days delivery keep spare inventory practical for rolling mills.
10. Purchase Decision Guide
Specify: thermocouple type and temperature range (R/S for the soaking zone, K for lower zones), protection tube material (SiC versus high-alumina), mounting length and flange or thread size, response time, and calibration certificates. Ask about lead times for spare assemblies - in reheating furnace service, a stocked spare is worth more than a lower price.
