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STRIP HEATERS Strip heaters clamp or bolt onto objects into order to heat a variety of materials. When used as radiant heaters, they include finned strips to maximize surface area and heat transfer to the air. Strip heaters consist of a heating element, protective sleeve, and mounting hardware. Sleeve, jacket or sheath materials include aluminum, iron, steel, stainless steel, aluminized steel, and zinc-coated steel. Many strip heaters are equipped with insulation to reduce heat losses to the environment. Common insulation materials include magnesium oxide, mica, fiberglass, minerals, and ceramic materials. There are several mounting styles for strip heaters. Some devices include mounting tabs with holes, mounting tabs with slots, or slots or holes without tabs. Strip heaters that include a butt case are placed in a milled slot between two steel plates to provide surface contact on both sides of the heater.
Selecting strip heaters requires an analysis of power requirements, electrical outputs, and physical dimensions. Maximum operating temperature, alternating current (AC) voltage, watts (W), and watt density are the most important power requirements and outputs to consider. Maximum operating temperature is the maximum temperature of the sheath, jacket, or sleeve. Watt density is the amount of wattage, per square inch, that a strip heater can deliver. It is calculated by dividing the available wattage by the heated area. As a rule, strip heaters with high watt density heaters should not be used with extremely viscous materials, materials that are not well-circulated, or explosive or volatile substances. Important physical specifications to consider when selecting strip heaters are strip length, strip width, and strip thickness.
There are many different termination types for strip heaters. Opposite end posts locate a post at each end of the heater. Tandem posts are in-line along the length of the heater while parallel posts are in-line along the width of the heater. Three-post terminals are similar to opposite end post devices, but position two posts at one end and one post at the other end. Horizontal leads run down the length of the heater. Terminal box connections are made through a protective enclosure on the surface of the strip heater. Other common termination styles for strip heaters use insulated leads, metal braided leads, and flexible conduit leads.
Strip heaters offer a variety of features. Products with a distributed wattage arrangement use a special coil pattern to concentrate heat distribution. Strip heaters with four enclosed sides are designed to prevent contamination. Devices that are made of corrosion-resistant materials are suitable for corrosive or caustic environments. Although most strip heaters include a protective sheath or sleeve, open-element heating elements are commonly available. Devices with ports, holes, or cut-outs allow the installation of instruments, thermocouples, or other temperature probes.
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