Optical Coil Protection – Temperature Monitoring of Induction Furnaces

Monitoring Refractory Linings – Dependable protection of the induction coil against overheating and, the more so, against contact with molten metal is of vital importance for ensuring safe and reliable operation of an induction furnace. Crucible cracks and erosion are detected and localised reliably and precisely and normal refractory wear is under close control.

Properly maintained refractory linings are essential for the safe operation of all metal melting furnaces: in induction furnaces, they are absolutely critical. The physics of electrical induction demands that the refractory lining between the induction coils and the bath be as thin as possible.

At the same time it must be thick enough to fully protect the coils and prevent metal run-out in the face of attacks by molten metal, chemical agents and mechanical shocks. Assuring that the furnace lining remains safely within manufacturer-specified limits requires careful treatment of the lining during all furnace operations along with comprehensive inspection and monitoring procedures.

Without question, metal run-outs, which occur when molten metal breaks through the furnace lining, rank among the most severe accidents that can occur during melting and holding operations. If cooling, electrical, hydraulic, or control lines become damaged, there may be an imminent danger of a fire or water/metal explosion. Continuously monitoring the integrity of the furnace lining is the key to preventing a run-out.

Monitoring Refractory Linings
LIOS has signed an exclusive supply contract with Otto Junker GmbH for the employment of fibre optic temperature measurement technology in melting- and heat-treatment facilities. The first result of this partnership is a newly developed OCP system (optical coil protection system) that was launched on the GIFA 2003. The OCP system provides a highly resolved real-time measurement of the temperature distribution of the exterior lining surface for the first time. Electrical measurement procedures are adversely affected by the electromagnetic disturbances that are always present in an induction furnace: purely optical signals are not. Thus, progressive wear of the lining as well as local defects can be detected reliably and very accurately utilizing DTS technology.

Additional benefits include:

• Prevention of operating interrupts caused by coil damages.
• Maximum operational safety with respect to serious damage and personal injuries.
• Monitoring of progressive wear and lining defects allows preventive measures, reducing downtime.
• Intuitive visualisation of the lining-condition.
• Full size data-recording and –management