Electricity and Control January 2021

MEASUREMENT + INSTRUMENTATION

Temperature monitoring for the steel industry In the iron and steel industry and in many foundry applications, temperature readings show whether processes are operating within their proper ranges, whether a reheater is too cold or too hot, whether a stand needs adjusting, or how much cooling should be applied. R&C Instrumentation advises that by using infrared non-contact thermometers, each stage can be monitored accurately so the steel retains the correct metallurgical properties as it travels through the process.

E very section of the steel manufacturing process can benefit from the use of infrared thermometers. The benefits include higher quality products, increased productivity, reduced energy costs, enhanced worker safe- ty, reduced downtime and easy data recording. Infrared sensors take temperature measurement one step further. Fast and accurate analogue and digital outputs allow temperature data to be integrated into the control sys- tem and simultaneously transferred for remote temperature monitoring and analysis. Smart sensors with digital elec- tronics and two-way communications can be configured remotely from the safety of the control room – especially important for metals with changing emissivity levels. A wide range of optics covers a variety of applications. This is supported by integrated through-the-lens sighting, and either laser or video sighting for correct target location. Infrared thermometers are used worldwide and in South Africa in many iron and steel applications. These include: continuous casting, reheating, rolling mills, cold mills, rod or wire mills, and other processes.

ƒ Continuous casting Accurate real-time temperature monitoring coupled with the ability to adjust water nozzles and water flow rates allows for proper cooling, which helps maintain the required met- allurgical properties in the steel. Fixed sensors, fibre optic sensors and line scanners are standard in this application. ƒ Reheating Reheating steel to a uniform temperature is critical to pre- vent deformation. Furthermore, uneven heating strains mill- ing equipment and can increase maintenance downtime. Measuring temperature inside a reheater with a series of temperature measurement devices enables the operator to check the reheater’s overall temperature and burner ef- ficiency. Once the slab or billet exits the reheating furnace, the ratio thermometers or line scanners (for wide slabs) transmit the temperature data immediately to the operator or controller, providing the information for milling operations to be adjusted to their correct settings. ƒ Rolling mills The different types of hot rolling mills and the number of stands in a process vary according to the product being manufactured. Infrared temperature measurement and scanning devices can be used effectively in scale break- ing, rolling stands, the down coiler and coil box, among Coiling is also often done at the end of the finishing stands, after cooling, and the coiled steel is transported to cold mills in another area in the plant or shipped to other facil- ities. Cold rolling makes a product thinner and smoother and is done while the steel is at around 100°C or at room temperature. Sensors mounted between each finishing stand allow the operator to detect temperature changes and make any adjustments required. ƒ Rod and wire mills In a typical rod and/or wire mill, billets are reheated and sent to a rolling mill to be reshaped as rods. From here, the rods go through a series of intermediate stands that reduce them to different sizes. Finishing stands reduce and smooth the rods into a product that can be further processed into hundreds of different products. Reheating a billet to a uni- other areas. ƒ Cold mills

Infrared thermometers provide temperature measurement solutions for every step in the steel treatment and manufacturing process.

18 Electricity + Control JANUARY 2021