Cartridges heaters with low voltage charge are the most recommended for moderate heating up to 300ºC. Made with the best quality stainless steel tube that can be found, or with other material such as copper, brass or aluminium. Everything is perfectly calibrated, such as the exterior. A long-life ceramic piece is inserted into the tube and stands up to every continuous temperature variation, together with the best possible thermal conductivity, as the piece is in contact with the wall of the tube, giving a perfect distribution of the heat.
Maxiwatt Model AC cartridge heaters are manufactured by means of compression for all their components, with the porpuse of lengthening their working life.
The conductor wire is wound spirally the hard ceramic body into which the conductor lead is inserted, with no connection (sometimes, a connection may occur on the outside of the cartridge heater). Ceramic discs and heads are inserted to obtain insulation and protection. Everything is coated with checked magnesium oxide to ensure a totla full cartridge heater. Later a process of compression and another of correction of the surface is carried out until the required measure is calibrated. Finally, a strict quality control is carried out to guarantee the best performance of the cartridge heater.
The most important element for ensuring the long life of the cartridge heater is the heating wire used in its manufacturing. Maxiwatt uses the best to be found anywhere in the market. After extensive research and years of experience it has been shown that a heating wire made of Ni-Cr 80/20 is both efficient and resistant to the formation of metallic coating brought out by oxidation. As the austenitil combination of nickel and chromium lacks iron, it is the most recommended for the heating wire.
For the induction of electricity a nickel cable (sheathed by fiberglass) is used. It is coated with silicone and fire-proof glazing. The cable wires are turned. Sometimes, the charge of the cartridge heater prevents the use of this type of connection. Finally, special procedures are used: threaded outputs with bolts, opposite outputs, etc. The different types of connection are shown on protections section
Magnesium oxide is used for insulation, and is the most suitable for insulating the heating wire and the conductor lead against the current of the sheath of the cartridge heater. When the space between the heating wire and the protecting sheath is too short, an insulator is required, this should be composed of the best qualities: purity, high degree of thermal cartridge heater, maximum melting point, uniform and exact compression, perfect thermal conductivity, etc, so that the best insulation is obtained. Control of the working temperature is essential. It must never exceed the working limits of the cartridge heater. It is very important to store the cartridge heater in a dry space because magnesium oxide is very hygroscopic. Just a few drops of water particles are enough to weaken considerably the insulating capacity of magnesium oxidebolts, opposite outputs, etc. The different types of connection are shown on protections section
The stainless steel 321 cover provides the highest quality to the manufacture of cartridge heaters. The materials which can be used in their manufacture are limited due to the strain caused by constant expansion due to the cooling and heating of the cartridge heater, the lack of a metal cover, which causes oxidation, and abrasive action. Stainless steel has been shown to be the most suitable material for the construction of cartridge heaters.
| Shealth material | Stainless steel 1.4541 |
|---|---|
| Heating conductor material | NiCr 8020 |
| Max. Shealth temperature | 750 ºC / 1380 ºF |
| Max. Voltage | 480 V |
| Wattage tolerance* | .+5% - 10% |
| High voltage resistance* | 1500 V AC at > 24 V operation voltage |
| 500 V at <= 24 V operation voltage | |
| Insulation resistance* | >= 5MW at 500 V DC |
| Leakage current | <= 0.5 mA at 253 V AC |
| Lenght 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] |
