Flow monitoring in arc furnaces

What are the challenges in monitoring the cooling circuit of furnaces?

The furnace wall is lined on the inside with refractory bricks and on the outside with copper pipes through which cooling water flows.
Water leaks into the furnace
Insufficient water for cooling
High water temperatures
Confined spaces
Risk of burning the multi-core cable

Traditionally, conductivity probes have been used to determine whether or not water is present. This was inexpensive and did not require a full pipe to measure the flow, but it was unreliable and could not be used to accurately measure flows. There was no local indication for comparison, and measuring the temperature required an additional PT100 probe.

ifm solution

DC arc furnaces are used in the production of ferrochromium, platinum, nickel etc. Typically, furnaces of two manufacturers are used, Takraf and Pyromet. Carbon rods are inserted into the raw material, causing an electrical circuit to generate heat to melt the raw material. Temperatures reach up to 1,200 °C:

ifm sensors ensure reliable, continuous, low-maintenance operation. Magnetic-inductive flow meters provide the information necessary to monitor the water flow in the cooling water circuit that protects the furnace walls
Precise measurement of flow, consumption and medium temperature of the cooling water
If water leaks into the furnace, hydrogen will build up, which may cause an explosion inside the furnace.
IO-Link modules collect the sensor signals in the flow circuit and transmit them to a controller. This reduces wiring costs and makes complex cable trees obsolete

Flow monitoring in arc furnaces

How to ensure process quality?

The pipe work is critical for the SM flow meter to function correctly, as it requires the proper upstream and downstream pipe lengths for accurate measurement. It also requires a fully filled pipe to function correctly. The SM flow meter operates according to Faraday’s law of induction. The conductive medium flowing through a pipe in a magnetic field (M) generates a voltage which is proportional to the flow velocity (v) or volumetric flow quantity. This voltage is picked up by electrodes (E) and converted in the evaluation unit. Its resistant materials make the sensor suitable for a multitude of media. A high protecting rating and a robust, compact housing distinguish the sensor in the field.

How to maintain process availability?

Depending on the type, each furnace can have between 50 and 400 temperature measurement points at which PT100 or thermocouples are installed.These are used at strategic points on the furnace wall to determine if the furnace lining is secure on the inside. If the lining starts to fail, the temperature rises. ifm offers a way to better wire type J or K thermocouples. The temperature of the thermocouple is converted into a digital signal and transmitted via IO-Link modules. There is no signal loss.

Protection against accidents involving people and equipment

If water leaks into the furnace, hydrogen will build up, which may cause an explosion inside the furnace. It is therefore important that this information is reported in time and transmitted promptly. IO-Link modules collect the sensor signals in the flow circuit and transmit them to a controller. This reduces wiring costs and makes complex cable trees obsolete. All information is returned to the SCADA system and the PLC via IO-Link.

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