In a steel plant, the temperature people talk about most is the furnace temperature. On the shop floor, though, most temperature sensors are installed in far simpler places: cooling water pipes, off-gas ducts, oil tanks, and coal silos. These points usually give the earliest warning when something starts to go wrong.
Steel plants generally follow one of two production routes. A blast furnace turns iron ore, coke, and limestone into hot metal, while an electric arc furnace (EAF) melts scrap with an electric arc. Because the processes differ, the temperature measurement points in each furnace are different too.
In a blast furnace, the furnace wall is protected by refractory lining that is water-cooled through staves or cooling plates. The outlet water temperature from each cooling zone shows how much heat is getting through the wall. If one zone rises while the others stay steady, the operations team has good reason to inspect the refractory in that area before the damage spreads. Gas ducts at the top of the furnace are usually fitted with temperature sensors as well.
An EAF behaves differently. Its wall panels and roof are almost entirely water-cooled, and the heat load changes quickly with each melting stage. Sensors on the cooling water outlet lines help identify panels that are short of flow. Around the furnace, the electrode hydraulic oil, the furnace transformer, and the off-gas extraction duct also need temperature monitoring.
The EAF area is known for heavy electrical interference. A millivolt signal from a thermocouple or a resistance change from an RTD is easily disturbed when run over a long cable straight to the control room. That is why sensors here are usually paired with a temperature transmitter that converts the signal to 4–20 mA close to the measuring point, keeping the reading stable at the PLC or DCS.
Before entering the furnace, raw materials are kept in silos or stockpiles. Coal stored for a long time can heat up on its own through oxidation, and the rise happens slowly from inside the pile. A sensor with a long probe that reaches into the silo can pick up this trend early. If the same silo already has a level transmitter, operators can see both the material quantity and its temperature on one screen.
Sensor selection should start from the data of each measuring point. For cooling water, lubricating oil, and hydraulic oil, an RTD Pt100 gives precise and stable readings. A Thermocouple Type K is better suited to off-gas ducts and other hot areas up to about 1,100 °C. Direct measurement of liquid steel, at around 1,500–1,650 °C, uses special methods and sensors and deserves a separate discussion.
The value of all this data shows once it reaches the control system. Through a PLC, DCS, or SCADA, temperature readings can trigger alarms, be logged as trends, or drive pumps and coolers automatically. Operators in the control room no longer need to walk up to the furnace area just to read a number.
CV. Rach Tekindo Makmur supplies Temperature Sensors & Temperature Transmitters for a wide range of industrial instrumentation needs. If you need sensors, transmitters, or consultation on configuration and installation for your temperature system, contact us on WhatsApp at 0877-8620-5656 to discuss your technical requirements and request a quotation tailored to your application.
