Cartridge Heaters: High-Performance Heating Elements
In many industries today, usage of heating appliances is a must, as provision of extra heat is crucial for some processes to take place, like molding, welding and soldering, etc. for the purpose of providing heat, cartridge heaters are excellent devices, with high heat transfer ability, with simple design and sophisticated performance. Cartridge heaters are heating elements consisting of: a basic helical coil made of a highly conducting alloy like the Nichrome, which is wound around a ceramic core, having coils which increase in number with the demand for increasing heating ability/ high watt-density.
The heaters are also provided with insulation, in which magnesium oxide filled in between the heater coil and the sheath in which the coil is placed. The tightly packed insulation allows for excellent heat transfer and lesser resistance temperature than other heating devices, and the magnesium oxide provides for high di-electric strength.
The sheath is another part of the cartridge heater which is in contact with the substance that is to be heated, and is made of several alloys like the stainless steel (304 and 316) and super-alloys like Incoloy, which has a high temperature rating that are useful in highly corrosive environments in which the heaters are used.
After the heater is filled with the insulating magnesium oxide, it is sealed at the open end to prevent any leakage of the insulating compound or any contamination of the heater with extraneous compounds.
Termination forms an important part of the heaters as these heating devices are installed or incorporated into various machinery equipment and clearances are to be met. The heaters are terminated with proper leads which are safely aligned and un-exposed to any temperature above their tolerance level.
Depending upon the type of machinery into which the heater is incorporated and the level of clearance to be provided, different types of lead wire is used, for example, fiberglass, silicone impregnated fiberglass and silicone rubber.
The functioning of the cartridge heater depends upon the watt-density, though high-performance does not mean a high watt-density heater. The heaters may be divided into different types based on the watt densities of the coils and their applications, namely, high watt-density, low watt-density and other types like split type heaters.
The high-watt density or heavy duty cartridge heaters enable high-watt application in smaller spaces, with the heavy-duty build providing excellent di-electric strength and high shock or vibration resistance that is required in some applications. The heaters are a correct fit in the holes, allowing for maximum heat transfer and minimum energy loss. The high watt density heaters are used in hot plates, platens, molding and plastic processing.
The low density cartridge heaters are another type, with lower watt-density, which come with brass sheaths and a braided lead wire and have uniform surface temperatures, which are useful in the packaging and processing machinery, extruders, molds and dies, medical equipment, etc.
Some heater manufacturers offer a split type, useful for high temperature applications, with highly efficient heating process and better clearance for insertion of the heater. This type of cartridge heaters is used in soldering, foundries, injection and blow molding, etc.
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