There is a direct correlation between the watt density of a cartridge heater and the amount of heat produced by the heater. Watt density is the number of watts per square inch of heated surface area of the heater. Obviously, tremendously high watt density can be produced in a heater, but the real issue becomes supplying a warrantable watt density. If the watt density is too high for an application, the heater will simply generate too much heat to effectively transfer and burn itself up.

Uniform and denser compaction of the Magnesium Oxide in a Watt-Flex® cartridge heater will allow a much higher warrantable watt density as compared to a conventional cartridge. We have samples of 3/8" diameter heaters at 85 watts per square inch that burn bright orange in open air all day at industrial shows. Expansion in the bore for more effective heat transfer to the host metal will also enhance the movement of heat away from the heater and, consequently, the life of the cartridge.

Larger diameter heaters are not as tolerant of higher watt density because the overriding concern becomes overall wattage. For example, a heater at 3/8 x 20" with a watt density of 100 will be about 2340 watts, whereas a 3/4 x 20" at the same watt density will be about 4720 watts. Total wattage and amperage can become compromising factors in the heater life. If you are considering a high watt density heater, give us a call for all considerations.