Standard cartridge heater design and heater life
Cartridge heaters provide localized heat for restricted work areas that require strict thermal control. Molds, pressing plates and various other types of processing equipment are effectively heated. By combining the location of the heater and proper power output, a tightly controlled operating temperature of up to 1400°F (760°C) can be achieved.
The life of the cartridge heater depends on the heat generated in the resistance wire can be effectively conducted away from the wire and into the heated part. Heat transfer efficiency is usually controlled by three factors:
- Resistance wire power density
- Density of insulating material around wires
- Install the heater to the heating part
Standard cartridge heater design
The nickel-chromium wire heating coil is inserted into the hole formed in the ceramic tube. The pure magnesium oxide filler is vibrated into the hole that houses the heating coil to transfer the heat to the stainless steel sheath to the greatest extent. Then, insert a Heliarc welding end cap at the bottom of the heater and install insulated wires. The MGO powder is not compacted, and the heat transfer is a function of the thermal conductivity of the particles to the grain, that is, to the heater sheath and then to the heating part. Therefore, the power density of the heating wire must be maintained in the low-medium range.
Cartridge heater fit
The most common cause of cartridge heater failure is improper assembly of its insertion hole. If there is air around the heater, which is an excellent insulation material, it will not be able to dissipate heat to the part with the best efficiency. The result is that the temperature on the Nichrome wire is much higher and malfunctions occur. The goal of extending the life of cartridge heaters is to adapt to the actual tightest fit of the specific application.
In short, if you want to use the longest life cartridge heater, please choose a forged heater, and ensure that the outer diameter of the heater and the inner diameter of the hole provide a tight tolerance for machining.