Temperature monitoring in a continuous casting plant

The Krupp Mannesmann GmbH (HKM) smeltery operates two continuous casting lines at their Duisburg location for the production of round bar steel to manufacture alloyed boiler tubes, ball bearing steel and other forging goods. The liquid steel is poured from the pan into a distributor and then flows through five or six water-cooled casting dies that form the continuously cast rounds (180 to 406 mm / 7 to 16 in). The steel is conveyed through the casting machine via four or five driver machines per strand.

Due to the continuously cast rounds, the area surrounding the first three driver machine rows behind the ingot mould in particular is heated up to several hundred degrees Celsius. The motors that power the driver machines must therefore be permanently cooled using fans and a cooling water circuit. It is also necessary to monitor the operating temperature of the expensive gear mechanism to prevent constant overheating (>50-60 °C / 122-140 °F).

New temperature meters were installed on one of the two casting lines. However, they could not withstand the extreme requirements and had to be replaced several times after only a few short weeks. HKM thus started looking for a stable, reliable temperature measuring solution for the 15 gear mechanisms in the first three motor series.

HKM made the decision to use 15 OPTITEMP TRA-P 14 resistance thermometers to monitor the temperature of the gear mechanisms. When it came to contact temperature measurement, Pt 100 temperature sensors were inserted approx. 100 mm / 4 in into the gear box via a clamp-compression fitting. The thermometer connection heads are mounted directly on the water-cooled cladding of the motor.

OPTITEMP TRA-P 14 connection heads are made of stainless steel. In addition, special heat-resistant gaskets as well as a suitable cable gland were used. The resistance signal is applied in the connection head to a temperature-resistant ceramic clamping socket. A thermal jacket then provides protective insulation for the cable and it is through this that the 4-wire resistance signal is forwarded to a central control room.

With the KROHNE OPTITEMP units, HKM once again has thermally-resistant thermometers that are constantly stable. They are capable of reliably monitoring the temperature development of the gears, even at high ambient temperatures. This way, the thermometers make a valuable contribution for steel specialists to the timely detection and avoidance of constant overheating and thus destruction of the expensive gearing mechanism on continuous casting. Using the Pt 100 sensors prevents prolonged interruption of the production process.