Electric Heating Elements: Cartridge Heaters

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Cartridge Heater Basics

Cartridge heaters are cylindrical in shape, consisting of an element made of resistance wire wound around a ceramic core. Within a metal sheath tube, the wound core is precisely centered and surrounded by granular magnesium oxide material. This isolates the resistance element from the tube electrically and provides a heat transfer medium to the sheath tube. At one end are electrical terminations. In order to enhance internal heat transfer and electrical insulation characteristics, higher performance, longer-lived cartridge heaters are swaged (a rotary hammer compacting process). Swaging compacts and densifies the granular insulating material, improving its thermal conductivity. Cartridge heaters are commonly used and are produced in a broad range of lengths, diameters, wattages, watt densities, lead agreements, and optional internal sensors.

Cartridge Heater Applications

Specialized Cartridge Heater (BCE)

The following equipment utilizes cartridge heaters: chromatography equipment; medical laboratory equipment, including chemistry analyzers; plastic molds and runners; platens; barrels on extrusion equipment; hot melt glue systems; packaging seal bars; labeling and marking systems; food-warming equipment and steamers; autoclaves; ovens; photographic processing equipment.

Cartridge heaters are capable of operating at elevated temperature as well as high watt density, but care must be taken to apply cartridge heaters at appropriate watt density and sheath temperature levels.

Temperature Capability

A maximum of 1600°F (870°C) sheath temperature is recommended.

Watt Density Capability

A maximum of 400 W/in. and higher under special conditions.  As a rule, cartridge heaters can operate at 1600°F at 40W/in.

Heater Life

Operating at 1600°F internal temperature with modest cycling and with the proper hole fit, a properly designed and constructed cartridge heater will provide approximately a one-year life.

Voltage

Usually 120/240V, with 480V and custom voltages requiring special design or sizing considerations.

Thermal Response/Application

Cartridge heater's thermal response is dependent on conductive heat transfer in most applications.  Optimum conduction requires close fit between the heater and the work to be heated. As heater looseness increases, watt density must be decreased accordingly, to prevent internal overheating. Watt densities of liquid-immersion cartridge heaters vary according to the liquid's viscosity and heat capacity.  When heating liquids, care must be taken to prevent "film boiling" where vapor bubbles create a thermal insulating effect and raise the heaters internal temperatures.

Heater Efficiency

Cartridge heaters are 100% efficient when immersed.

For more information about electric heating elements, contact BCE by calling 510-274-1990 or by visiting https://bcemfg.com.

Miniature Cartridge Heaters

Miniature cartridge heaters are roughly defined as electrical cartridge heaters 3" or shorter in length, having diameters of 1/8", 5/32", or 3/16", and providing high watt densities (although low to medium watt densities are available). Their exterior construction is usually 304 or 316 stainless steel, with internal nickel chromium (Nichrome) resistance wire. A variety of electrical lead wire configurations to meet the needs of the application are available. Because of their swaged (machine compressed) construction, miniature cartridge heaters provide a high level of shock and vibration resistance, as well as good dielectric strength.

Miniature cartridge heaters are used to provide localized, concentrated heat to small component parts or in restricted work spaces. Dies and platens, as well as a variety of other types of OEM processing machinery, are efficiently heated by miniature cartridge heaters.

Typical OEM Uses for Miniature Cartridge Heaters

• Gas monitoring equipment / analyzers
• 3D printing machine
• Medical equipment and devices 
• Ink printing and labeling machines
• Mass spectrometers
• Analytical process instrumentation
• Optical equipment
• Gas chromatography

Operating temperatures as high as 1200 deg. F can be attained with careful attention paid to the application. Miniature cartridge heaters are almost always mounted in a close tolerance holes or swiftly circulating fluids because their often very high power densities would cause them to self-destruct if run full power in open air or stagnant fluids. As with all cartridge heaters, lifespan is directly proportional to the success or ability to move the heat from the internal nickel chromium resistance wire into the heated part or process. Therefore, careful consideration must be giving to hole tolerances or process flow rate before application.  It is common for miniature cartridge heaters to include internal thermocouples for temperature control and limiting purposes.

For more information about miniature cartridge heaters, contact BCE.
https://bcemfg.com
510-274-1990