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Pencil heaters are used mainly in immersion applications; however, due to their compact cylindrical shape, they can also be used in a variety of other applications. Important parameters to consider when specifying Pencil heaters are maximum operating or sheath temperature, AC voltage required, watts and watt density. Maximum operating temperature is the maximum temperature that the sheath covering the Pencil heater may reach. Note that the maximum sheath temperature is not the hottest temperature that a heated substance may reach. AC voltage is the minimum alternating current (AC) volts required to operate the Pencil heater. Watt density is the amount of wattage per square inch that a Pencil heater can deliver. Suppliers calculate watt density by dividing the available wattage by the heated area. High watt density heaters should not be used with extremely viscous materials, poorly-circulated materials, or explosive/volatile materials due to risk of fire. Important dimensions for Pencil heaters are the nominal diameter and Pencil length or heated length.
A Pencil heater equipped with a layer of ceramic insulation can resist heat and chemicals. Ceramics are made of nonmetallic minerals, such as clay, that have been permanently hardened by firing at a high temperature.
Pencil heaters differ in terms of electrical connectors, termination types, mounting styles, and optional features. Not all heaters have termination angles. Straight leads or terminals make straight connections with the Pencil heater. In other words, there is no angle. Right angle leads or terminals are angled 90 degrees from the initial connection with the Pencil heater. Termination type represents the electrical connection options available for Pencil heaters. Most devices can be configured with many different termination options. Choices for termination type include: bare leads, insulated leads, armor cable leads, metal braided leads, flexible conduit leads, screw terminals terminal boxes, quick disconnects and plugs. Pencil heaters may be mounted or installed using different methods. Some products have multiple mounting options, such as threaded pipe fittings, mounting flanges and locating rings.
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