Sheath
Insulation
The heating coil is the actual resistance which is where the electrical load occurs. The most common type of metal alloy used for this purpose is a nickel-chromium mixture, also known as nichrome. The nichrome wire is wound around a ceramic core, and the number of spirals per inch vary according to the requested watt density. Potential from an alternating current source, which can either be 2 phase or 3 phase, flows through the coiled nichrome wire, heating up the wire, which in turn, heats the cartridge heater sheath.
Construction
Cartridge Heater
Insulation is used to prevent the nichrome coil contacting the sheath, an event that would ground the resistance and could produce a catastrophic short-circuit, resulting in a melted sheath and a major equipment failure. Damage can be mitigated by installing a ground fault interrupting circuit. To prevent the coil from touching the sheath, the coil is inserted into the sheath, and immediately filled with magnesium oxide (MgO). To ensure the MgO fills the empty space between the sheath and the coil, the cartridge heater is filled under vibration.
Depending on the clearance and the design of the machine where the cartridge heater will be inserted, the type of wire used will vary. Fiberglass is the commonly used for cartridge heaters and other high-temperature applications, such as automotive wiring harnesses and industrial equipment. Other variants used are silicone impregnated fiberglass and silicone rubber. It is a type of wire.
-
Seal bars -
Torpedo heaters for injection molding -
Injection molding manifolds -
Mass spectrometry -
Rubber molding -
Food production -
Immersion tank heating -
HVAC compressors -
Fuel cells -
Semiconductors -
Medical devices -
Sensor measurement devices -
Extrusion -
Die casting -
Hot melt adhesives -
Heat staking / hole punch -
Plastic welding -
Fluid heating -
3D Printers
Cartridge heaters are found useful in many applications,such as
Heating Coil
The sheath is the part of the cartridge heater which makes contact with the material or substance to be heated. Several metal alloys are used, depending on the type of application, such as highly acidic or corrosive environments. The most common types of sheaths are 304 stainless steel, 316 stainless steel, and incoloy 800. Incoloy has the highest temperature rating, and is considered a superalloy.
Sealing
Termination
Lead wire type
After the cartridge heater has been filled with MgO, a seal is applied to the open end of the cartridge heater (where the nichrome coil was introduced). This prevents the coil and the MgO from coming out, as well as preventing contaminants such as plastic debris, air, or moisture from entering the heater.
Since cartridge heaters are installed in a wide variety of machines, manufacturers must design the heaters to meet certain clearances. [dead link] The cartridge heaters might be terminated with the leads coming out straight, or in a right angle. Also, manufacturers must be careful that the leads are not exposed to temperatures higher than the maximum rating for the lead wire. In order to prevent lead wire damage from temperature, movement or contamination, the lead wire can be protected with a metal conduit, braided metal or silicone sleeves.
Cartridge Heaters Metric – Description
Metric & Imperial high density cartridge heaters are round tubular heaters with electrical terminations on one side. These dependable heaters are made to withstand tough industrial usage. With a tolerance of +/-0.002" on its outside diameter to secure a tight fit inside receptacle holes, and rock hard compaction of MgO insulation through swaging, these heaters can attain 1500ºF sheath temperature. High density cartridge heaters are available with various termination styles and mounting attachments. In high-density cartridge heaters the resistance wire loops are positioned as close as possible to the outside shell. Because the MgO powder insulation around these loops is compacted by swaging and transformed into a very hard medium, heat transmission is very efficient.
Metric and Imperial cartridges can have up to 200 w/in watt densities.
Cartridge Heaters are usually supplied with lead wires. The attachment of the leads to the central pins is done internally, in a 3/8” cold section. In excessively hot applications the length of this cold section could be increased. To facilitate installation and avoid
excessive air pockets, cartridge heaters are made 0.004” less than the nominal size of the receptacle hole with a tolerance of +/- 0.002”. Metric and Imperial cartridges can be dual-voltage, three-phase, and/or be supplied with a ground terminal. With ten different
termination styles, mounting attachments and various optional features, Our high density cartridge heaters are widely used in numerous high temperature applications.
Cartridge Heaters -Specifications and Watt Density
Built-in thermocouples:
One optional feature on cartridges is built-in thermocouples. These could be type “J” or “K”, grounded or ungrounded, and attached either at the disc end or middle of the cartridge.
Graphite coating:
To facilitate their installation and removal, cartridges could becoated with a graphite-like substance. This solid lubricant doesn’t increase the outsidediameter, and is suitable for temperatures up to 750 degrees F.
Moisture and contamination proofing:
To protect cartridge heaters against moisture and contamination, Teflon lead wires are used and the lead end is sealed using Epoxy, RTV silicone or Teflon. The temperature limitation is 480 degrees F.
Distributed wattage:
In applications such as sealing bars or rubber molds, the two ends of a cartridge heater are usually colder than the middle. To overcome this inconsistency and have a uniformly distributed heat source, cartridges could be made to have higher wattages at the ends. 35/30/35 is a common wattage distribution.
Center-less grinding:
In applications where superior heat transfer is required, the tolerance on the outside diameter could be improved to +/- 0.001” by center-less grinding.
Zones and cold sections:
We can also manufacture cartridges with cold sections and separate zones that can be controlled independently.
Cartridge Heaters - Optional Features
Tell me all the things you want to do ！
