Refractory Wear Monitoring System Betters Lining Life, Reduces Furnace Damage.

The refractory lining in furnaces is consumable. Hidden wear and uncontrolled penetration of the melt into the refractory can cause damage to the furnace, create production stoppages and produce safety hazards for employees. One solution presented by Saveway Corp., Wyomissing, Pennsylvania, is the Saveway Lining Wear Monitoring System, which incorporates sensor electrodes into the furnace refractory system to perform analysis.

As the melt penetrates the refractory lining, there is an increase in temperature, which results in a reduction of the electrical resistance of the refractory material. The lining monitoring system relates the measured resistance as a function of temperature to determine residual wall thickness and monitor lining life.

For installation in an induction crucible furnace, the measuring electrodes are integrated into a sensor mat (electrode plate) as two engaging comb-shaped electrodes. The standard design of the electrode plate consists of two flexible mica materials, with the material facing the melt possessing the same resistive properties as the refractory material. The electrode plates for crucible induction furnaces are 500 mm wide and are adapted to the height of the coil.

The electrode plate is placed on the coil grouting instead of the conventional slip plane or insulating layer. Since the electrode plate is a consumable, it has to be changed during relining as the wear is indicated on a matrix display or computer. The shortest distance between the melt and the electrode wires always is indicated for the area of the whole sensor mat.

The result from the lining monitoring system is: an increased service life of the refractory because hidden wear is made apparent and it can be fully utilized without any risk. Also, determining the causes of abnormal lining wear becomes easier due to the transparency of refractory with the monitoring system. The system is able to monitor several furnaces running together or separately using one control unit.

The monitoring system runs on WindowsNT software and has the ability to compile data from various furnaces and perform analysis.

According to the manufacturer, the furnaces monitored by the system have not exhibited undetected melt penetration in its 6 years of field experience. In addition, for induction furnaces of less than 20 tons, testing thus far has proven that the monitoring system increases lining life by at least 20%.

Up to now, the monitoring systems have been installed on induction crucible furnaces, however new applications include holding, channel induction and arc furnaces.