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DuraWatt: Cartridge heater

Maxiwatt swaged cartridges

High watt density cartridges.
They provide a great uniform distribution of heat, and are hermetically sealed, which considerably increases the long life of the heater as well as prevents the oxidation of the heater wire even at high temperatures. Over 8000 configurations in high density available.
High watt density Maxiwatt cartridges are manufactured from the highest quality materials undergoing the strictest safety and quality controls in accordance with the international standards.

  • Long-life
  • High temperatures
  • Maximum watts density 258W/inch2
Acabados, Ends Protecciones, Protections Stock 24h

Internal options

Termocopia, Termocouple Distribución de Watios, Watt distribution Zonas interactivas, Inactive Areas Diferencia de voltaje, Different voltages

Technical data

Heat intensity Not exceeding 258W/inch2 (advisable)
Power Depends on the dimension
Exhaust extreme (when cold) <=0.1mA to 242 v.
Insulation (when cold) 5 Min Ohms 500 Watts minimum
Dielectric strength 1500v. 1/sec
Working temperature 1382ºF max.
Length tolerance +/-1.5%
Diameter tolerance -0.00079 to -0.0024 inch
Cut off connection tolerance +/-0.59 inch
Power tolerance (w) + 5 % - 10 %
Cold areas Depends on length and diameter 0.20-0.98 inch


Durawatt cartridge heaters are manufactured utilizing a swaging process to compress their components, with the purpose of lengthening their usable life.
The conductor wire is wound around a hard ceramic core which provides a conductor coil without successive connections (in some cases, a connection may occur on the outside of the cartridge). Ceramic discs and heads are utilized to provide insulation and protection. Everything is covered with pure, granular magnesium oxide to ensure a completely full cartridge.
Next the heater undergoes a swaging process and another straightening process until the required tolerances are achieved. Finally, a strict quality control inspection is carried out to guarantee the highest performance of the cartridge.

cartridge heater
  1. Welded watertight base (Tig) to endure pressure up to 853 lbs/inch2.
  2. Calibrated stainless steel AISI 304/316/321/ INCOLOY.
  3. Ceramic disc insulator.
  4. Pure grain sized magnesium oxide.
  5. Nickel-chromium 80/20 heating wire. Melting point 2552ºF.
  6. Ceramic core.
  7. Hard ceramic head.
  8. Conductor lead.
  9. Hard refractory paste.
  10. Conductor coil without connections.
The exclusive Maxiwatt manufacturing process utilizes near perfectly concentric coils and, in conjunction with its system of electronically spacing the gap between each spiral, delivers consistent, uniform temperature not only along the length of the cartridge, but also around the circumference. This uniform temperature improves its usable life and durability.   cartridge heater cartridge heater


They are able to resist the toughest work conditions, such as vibration, moisture, fluid, spills, frequent expansion and where temperatures of between 752ºF and 1382ºF are required, or temperatures within a tight range


  • Molds
  • Smelting of materials
  • Heating of fluids
  • Heat welding, etc

Specifications for consideration

When solids, liquids, and gases need to be heated by electric energy the process is generally carried out by conduction. It is only possible to transmit heat quickly by conduction if the producer of the heat (the cartridge) is in direct contact with the heat sink (any solid, liquid, or gas).
When heating occurs, the molecules expand and move faster, producing a distribution of heat to the colder part until their temperatures level is equal.
In cases where there is a mold which has been drilled in order to hold a cartridge heater, and where the mold is not meant to be in direct contact with the entire cartridge heater, heating takes place by conduction  due to the fact that the air molecules would not transmit the energy required to heating the mold. The heat would not be distributed but would remain within the cartridge heater, producing overheating of the same, which would cause a reduction of the dielectric strength between the heating wire, the power conductors, and the metal shield, resulting in a short-circuit. It is therefore very important to ensure the sizing of the cartridge is in accordance with the mass to be heated.


When dealing with a high-density cartridge heater, the exact amount of the required wattage must be carefully considered for proper function and  a long useable life of the cartridge heater.
The Maxiwatt cartridge heater is designed in a way that considers the natural aging of the heater coil and its nature, in conjunction  with the nominal wattage of the cartridge heater.
The coincidence of the real power at the rated power is done by a special selection process which selects only chooses those cartridge heaters having a power tolerance corresponding to 7% of the rated power.

Power at. Cold state Hot State Power at.
D. & length 230 V. Ohms Value Ohms Value 230V. Variation
0.394x3.150 315 W 167.94 174.15 303.76 W -3.7
0.394x3.937 400 W 132.25 136.34 388.00 W -3.1
0.394x5.118 500 W 105.80 108.55 487.33 W -2.6
0.492x3.150 400 W 132.25 136.21 388.37 W -3
0.492x3.937 500 W 105.80 108.02 489.72 W -2.1
0.492x5.118 800 W 66.13 67.32 785.80 W -1.8
0.630x3.150 630 W 83.97 85.64 617.97 W -2
0.630x3.937 1000 W 52.90 53.69 985.29 W -1.5
0.630x5.118 1100 W 48.09 48.52 1090.27 W -0.9
0.787x3.937 1000 W 52.90 53.44 989.90 W -1
0.787x5.118 1250 W 42.32 62.65 1240.33 W -0.8

Stainless steel 321 sheath

The stainless steel 321 sheath 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 dilation 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 best material for the construction of cartridge heaters.

Total insulation

Insulation is made with pure Magnesium oxide. This material is the best used for insulating the heating wire and the conductor coil from the current and the sheath of the cartridge. 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 thermal resistance, 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 cartridge’s working limits. It is very important to store the cartridge in a dry place because magnesium oxide is very hygroscopic. Just a few drops of water particles are enough to considerably weaken the insulating capacity of magnesium oxide.

Ni-Cr 80/20 heating wire

The most important element for ensuring the long life of the cartridge heater is the heating wire used in its manufacture. Maxiwatt uses the highest quality available anywhere. After extensive research and years of experience it has been proven that a heating wire made of Ni-Cr 80/20 is both efficient and resistant to the formation of metallic coating brought on by oxidation. As the austenitic combination of nickel and chromium lacks iron, it is the most recommended for heating wire.

Conductor lead

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 application of the cartridge heater prevents the use of this type of connection. At the end, special procedures are used: threaded posts with bolts, opposite outputs, etc.
The different types of connection are shown in protections section


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