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COIL HEATERS Coil heaters are heating elements formed from straight, uncoiled segments of heating cable. Forming straight cables into patterns increases the surface area and heat transfer capability, but also requires increased energy and watt density. Most coil heaters operate on AC voltages. Some include a grounding wire or provide distributed wattage arrangements to concentrate heat distribution. Coil heaters can be configured with different termination options. For example, electrical connections can be made via a plug configuration and protected by a terminal box interface. Armor cable, metal braids, and flexible conduits are used to protect insulated leads.
There are a variety of shapes and sizes for coil heaters. Some devices are straight, square, or rectangular. Others are round, coiled, spiral wound, or star wound. Spiral wound heaters are used to generate high temperatures in restricted areas. Star wound cables are offset coils inserted into pipes or ducts to create a turbulent flow in air or fluid. In terms of measurements, coil heaters vary according to coil inner diameter, outer diameter, length, and width.
Coil heaters are made from several different types of materials and typically include insulation. Sleeve, sheath, and jacket materials include aluminum, brass, copper, iron, nickel alloy, steel, and stainless steel. Insulation materials include ceramics, mica, minerals, and fiberglass. Mica is highly resistant to acids while fiberglass is impervious to many caustics. Some coil heaters may be fully or partially immersed in heated substances, while others are corrosion-resistant or suitable for cryogenic use. Clamping straps provide additional protection for coils and connections.
There are many applications for coil heaters. For example, larger devices are used in plastic injection molding machines, holding tanks, metallurgical analyzers, and pulp and paper processing. Coil heaters are also used in blow molding machines, oil reclamation equipment, and food and candy extruders. Smaller, localized devices are used in labeling, bag sealing, hot stamping, and packaging equipment.
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