Special heating systems

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Induction systems for the surface heating of cylinders
on paper production lines

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The heating of the cylinders by means of an induction system is based on the Joule effect, generated by the currents induced in the mantle of the cylinder and due to the variable magnetic field produced by an inductor that can be inside or outside the cylinder.

In the technologically advanced field, industrial cylinders must have an unvarying and constant temperature, which is an essential feature for the following processes:

• drying
• rolling
• stabilisation
• calendering
• application of adhesive film to a material

It is possible to meet these requirements only with an induction system. The reasons for which these results are reached are:

• heat is generated directly into the cylinder
• the cylinder surface heats immediately
• the surface temperature is controlled with precision
• heat is distributed evenly over all the external surface, regardless of the cylinder position and the environmental working conditions

The economic advantages of an induction system compared to one that uses oil or steam as a thermal vector fluid are numerous. A few that can be mentioned are:

• low installation cost
• primary energy saving
• temperature maintenance
• easy to use
• simple manufacturing

Frequency converters for the heating of epitaxial reactors used in the semi-conductor production process

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Frequency converters (150 kW / 4 kHz) to heat graphite crucibles used in systems for the production of semi-conductors.

Two-stage modular station for the heating of aluminium alloy billets until the thixotropic status

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The term “Thixotropic” is referred to a “solid-liquid” whose viscosity diminishes with the increase of the cutting stress. In recent years, intense research has allowed the arrival of thixo-technology for industrial purposes.

After homogeneous induction heating at a well-defined temperature and before being pressed, thixotropic aluminium alloy billets are in a specific condition of partial solidification.

By pressing a billet when it is in this specific status of “solid-liquid”, the end product shows a drastic reduction of all defects in pressure die casting systems.

In the process of forming billets with thixotropic properties, it is essential that the temperature distribution is almost even throughout the workpiece at the end of the heating. The heating process simulations have been carried out, given the symmetries, on a quarter of a billet.