Ceramic covered rolls

Bare roll treater rolls are typically specified to have smaller diameters than those of covered roll systems, because of the area of dielectric required to dissipate the heat generated in the corona. With bare roll systems, the diameter is dictated by the length of the roll (driven by the maximum material width to treat) and the number of electrodes required (specified by the Watt density requirement). This dielectric-less ground roll design is always paired with dielectric-surfaced (typically ceramic) electrodes to promote uniform corona discharging to both conductive and non-conductive material surfaces. 

Comparing universal roll system performance to systems utilizing Hypalon , silicone, and epoxy covered rolls, the higher efficiency ceramic coating requires less power to achieve the same surface tension results, therefore reducing the cost of the power supply required. 

Figure 80 Types of treater for applying corona discharge (a) for non-conductive substrates, with an earthed base roll covered with a dielectric (b) for material of all types, with a bare, earthed base roll and the dielectric on the discharge electrode The main components are (1) Multi-fin electrode (2) Electrode tube in ceramic or quartz (3) Earthed base roll covered with dielectric (4) Bare, earthed base roll (5) Housing for the electrode assembly, enabling the extraction of ozone and cooling of the electrode (6) Path of material being treated...

Mitsui Mining Smelting Co., Ltd. (MMS) is a general non-ferrous metal enterprise which originated its business from mining and smelting. At present, its spectrum of business activities covers not only the production of zinc, lead, copper and other materials but also it has extended its applications to the production of rolled copper products, synthetic chemical products, electric circuit materials (electrolytic copper foil), PVD (physical vapour deposition) materials, battery materials, ceramics, rare metals, rare earth and automotive components. 

The dielectric layer for ceramic capacitors is formed by preparing a barium titanate paste that is rolled into a flexible film. The film is covered by conducting ink to form the electrode layer. Then the film is cut, stacked into layers, and the procedure is completed in a manner similar to that already described. 

Although highly insulative roll coverings, such as ceramic, cost more when compared to silicone sleeve roll coverings, they offer a more precise roll covering... 

Table 4.1 Performance Comparison - Silicone vs. Ceramic Roll Coverings...

It is important that metal or metallized surfaces be in contact with a clean and grounded idler roll along its path through the corona treater. This idler roll can be covered with conductive ceramic to prevent oxidation and provide a ground path from the conductive material surface. 

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