Low-voltage cartridge heaters are recommended for moderate heating up to 300ºC. Made with the highest quality stainless steel tubing available, or other materials like copper, brass, or aluminium. Everything is precisely calibrated, including the exterior. A long-life ceramic piece is inserted into the tube and withstands all continuous temperature variations, with the best thermal conductivity possible since it contacts the tube wall, allowing perfect heat distribution.
Maxiwatt cartridge heaters Model AC are manufactured by compressing all components to extend their lifespan.
The conductor wire is wound in a spiral on a hard ceramic core into which the conductor is inserted, without a connection (although sometimes a connection may occur outside the cartridge). Ceramic discs and heads are inserted for insulation and protection. The whole is filled with verified pure magnesium oxide to ensure a completely filled cartridge. Afterwards, a compression and surface correction process is carried out until the required size is calibrated. Finally, strict quality control is performed to ensure the cartridge’s optimal performance.
The most important element in ensuring the long lifespan of the cartridge heater is the heating wire used in its manufacture. Maxiwatt uses the best available on the market. After extensive research and years of experience, it has been proven that a heating wire made from Ni-Cr 80/20 is effective and resistant to the formation of a metallic layer caused by oxidation. As the austenitic combination of nickel and chromium contains no iron, it is the most recommended for heating wires.
A nickel cable (coated with fibreglass) is used for the induction of electricity. It is coated with silicone and fireproof glazing. The wires in the cable are twisted. Sometimes, the load of the cartridge prevents the use of this type of connection. Finally, special procedures are used: threaded outlets with bolts, opposite outlets, etc. The different types of connections are shown in the protections section.
Magnesium oxide is used as an insulator and is best suited for insulating the heating wire and conductor against the current in the cartridge sheath. When the space between the heating wire and the protective sheath is too short, an insulator is required. This must be of the highest quality: purity, high degree of cartridge thermal heater, maximum melting point, uniform and accurate compression, perfect thermal conductivity, etc., in order to obtain the best insulation. Controlling the working temperature is essential. It must never exceed the working limits of the cartridge. It is very important to store the cartridge in a dry place, as magnesium oxide is highly hygroscopic. Just a few drops of water particles are enough to significantly weaken the insulating capacity of magnesium oxide: bolts, opposite outlets, etc. The different types of connection are shown in the protection section.
The stainless steel 321 casing provides the highest quality in the manufacture of cartridge heaters. The materials that can be used in their manufacture are limited due to the stress caused by constant expansion from heating and cooling, the lack of a metallic casing (which leads to oxidation), and abrasive action. Stainless steel has proven to be the most suitable material for building cartridge heaters.
| Protective material | Stainless steel 1.4541 |
|---|---|
| Heating conductor material | NiCr 8020 |
| Max. storage temperature | 750 ºC / 1380 ºF |
| Max. voltage | 480 V |
| Power tolerance* | .+5% - 10% |
| High voltage resistance* | 1500 V AC at > 24 V operating voltage |
| 500 V at <= 24 V operating voltage | |
| Insulation resistance* | >= 5MW at 500 V DC |
| Leakage current* | <= 0.5 mA at 253 V AC |
| Length tolerance | A 1.5%, min A 1mm |
| Standard diameter tolerance | metric -0.02 / -0.06 mm |
| inch: A 0.79 mils [A 0.02 mm] |
