Cartridge heaters are generally used in immersion applications. However, due to the compact cylindrical shape of cartridge heaters, they can also be used in a variety of other applications.
Important parameters to consider when specifying cartridge 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 heater may reach.
The maximum sheath temperature does not represent the maximum temperature that a heated substance may reach. AC Voltage required represents the minimum AC Voltage required to operate the heater. Watts represents the maximum wattage available from the heater. Watt density is the amount of wattage, per square inch, the heater is capable of delivering. Watt density is calculated by dividing the available wattage by the heated area. Watt density is a good measure of the heater’s ability to quickly heat a substance. High watt density heaters should not be used with extremely viscous materials, materials that are not well-circulated, or explosive/volatile materials due to risk of fire. Important dimensions for cartridge heaters are the nominal diameter and cartridge length or heated length.
A sleeve, jacket or sheath is a protective outer covering for the heating elements. Some heaters will have multiple material options available. The sleeve material of cartridge heaters can be one of many types including aluminum, brass, copper, iron, nickel alloy, stainless steel, and steel. Heater insulation reduces heat loss to the environment. Some heaters may be available with multiple insulation options. Insulation options for cartridge heaters include no insulation, ceramic insulation, mica insulation, mineral insulation, and fiberglass. An uninsulated cartridge has a lower profile and is useful in areas where space is at a premium. An uninsulated cartridge, however, is not particularly energy efficient. A cartridge heater equipped with a layer of ceramic insulation resist heat and chemicals. Ceramics made of nonmetallic minerals, such as clay, that have been permanently hardened by firing at a high temperature. Mica is known for its high resistance to heat and acids, and electrical insulating properties.
Cartridge heaters may have different options for configuration of electrical connectors. Not all heaters will have optional termination angles. Straight leads or terminals make straight connections with the heater, there is no angle. Right angle leads or terminals are angled 90 degrees from the initial connection with the heater, for ease of installation and use. Termination type represents the electrical connection options available for the heater. Most heaters can be configured with many different termination options. Termination types available for cartridge heaters include bare leads, insulated leads, armor cable leads, metal braided leads, flexible conduit leads, screw terminals terminal boxes, quick disconnects and plugs. A cartridge heater may be mounted or installed using many different methods. Some heaters may be available with multiple mounting options. Mounting options for cartridge heaters include threaded pipe fittings, mounting flanges and locating rings.
Features common to cartridge heaters include cooling options, internal temperature detectors, cryogenic use, grounding wires, unheated sheath extension, split sheath style, bolt heater, explosion resistant, and corrosion resistant.