Cartridge heater

Cartridge Heater Introduction
– A cartridge heater is a tube-shaped, heavy-duty, industrial Joule heating element.
– It is used in the process heating industry and is custom manufactured for specific watt density.
– Compact designs can reach a watt density of up to 50W/cm².
– Specialty high temperature designs can reach 100W/cm².
– The heating coil, made of a nickel-chromium mixture, is wound around a ceramic core.

Insulation
– Insulation prevents the nichrome coil from contacting the sheath, which could cause a short circuit.
– Ground fault interrupting circuits can mitigate damage from a short circuit.
– To prevent coil-sheath contact, the coil is inserted into the sheath and filled with magnesium oxide (MgO).
– Vibration is used to ensure proper filling of MgO between the sheath and the coil.
– Proper insulation prevents equipment failure and melting of the sheath.

Sheath
– The sheath is the part of the cartridge heater that makes contact with the material to be heated.
– Different metal alloys, such as 304 stainless steel, 316 stainless steel, and incoloy 800, are used for different applications.
– Incoloy 800 is a superalloy with the highest temperature rating.
– The choice of sheath material depends on the specific application’s requirements.
– Sheath selection is crucial for performance and durability in different environments.

Sealing
– After filling the cartridge heater with MgO, a seal is applied to the open end.
– The seal prevents the coil and MgO from coming out of the heater.
– It also prevents contaminants like plastic debris, air, or moisture from entering the heater.
– Proper sealing ensures the integrity and functionality of the cartridge heater.
– The seal is essential for maintaining the heater’s performance and protecting it from external factors.

Termination
– Cartridge heaters are designed to meet specific clearances in various machines.
– Termination options include straight leads or leads with a right angle.
– Manufacturers must ensure that lead wires are not exposed to temperatures exceeding their maximum rating.
– Lead wire protection options include metal conduit, braided metal, or silicone sleeves.
– Proper termination prevents lead wire damage and ensures safe and reliable operation. Source:  https://en.wikipedia.org/wiki/Cartridge_heater

Cartridge heater (Wikipedia)

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A cartridge heater is a tube-shaped, heavy-duty, industrial Joule heating element used in the process heating industry, usually custom manufactured to a specific watt density, based on its intended application. Compact designs are capable of reaching a watt density of up to 50W/cm² while some specialty high temperature designs can reach 100w/cm².

Cartridge Heater
From top to bottom: Square cartridge heater, cartridge heater with threaded NPT fitting (tapered threads), "mini" cartridge heater.
Industry	Process heating