Hotco cartridge heaters
provide a convenient, dependable and efficient method of applying concentrated heat to solid
metal components particularly where compact, insert type heating is desirable such as die blocks, moulds, platens, heat sealing tools or
practically any application. Cartridge heaters
are readily adaptable to a wide variety of special requirements, sizes or
ratings. Typical applications include heating liquids such as water, oil and glues; gases such as air and solids such as metal dies.
Renowned for long trouble free service, cartridge heaters are constructed using sheaths of precision dimensions
and tolerances for intimate contact with reamed holes. Internal heating elements are supported on high quality ceramic, solidly packed
magnesium oxide with a wide variety of connections available, including plated steel screws and nuts or glass insulated nickel wires. Heating
elements positioned close to the outside surface for maximum heat transfer, minimum core temperature, and faster heating. High
watt-density units with stainless steel sheaths provide stable non-oxidising surfaces.
The surface watts density (the power in watts per unit area on the cartridge tube) and operating
temperature of a cartridge is related to the hole clearance. The larger the hole clearance the lower the recommended watts density.
A good hole/cartridge fit cannot be over-emphasised, the better the fit the longer the element's service life. Cartridge heaters
rated at over 20 watts per square centimetre the cartridges should be clamped in position.
Types of Cartridge Heaters
Compacted Cartridge Heaters
Compacted cartridge heaters consist of resistance wire wound on a refractory rod and inserted into
a stainless steel tube and the remained space filled with magnesium oxide. The tube is reduced in diameter to compact the contents and then
machined to precise tolerances on diameter and straightness.
Always ensure high density cartridge heaters are fitted into accurately reamed, parallel sided holes to ensure proper performance.
Non-Compacted Cartridge Heaters
Non-compacted cartridge heaters are manufactured by supporting helically coiled resistance wire in high quality refractory formers. The assembly is inserted into a tube which
is manufactured to precise tolerances on diameter and straightness, completely filled with magnesium oxide and sealed.
Cartridge Heater Applications
- Water Heating
We recommend 10 watts per square centimetre when cartridges are to be
immersed in water because the water removes the energy from the element
very effectively. Commonly used as a chemical solutions heater.
- Oil Heating
Commonly used as engine sump heaters. When heating some oils, only 2 watts per square centimetre can be used
otherwise the high cartridge heater surface temperature causes the oil to
oxidise and carbon to be built-up on the surface of the heater. When this occurs, the carbon can thermally insulate the cartridge heater, causing
the unit to heat up internally, often resulting in electrical failure.
- Air Heating
Elements of approximately 1 watt per square centimetre are suitable for
convection air heating, eg. Anti-condensation heaters.
- Die Heating
Manifolds, hot runners and torpedoes.
Hot melt glue applicators.
Controlling Cartridge Heater Temperature
To ensure that the element does not fail through overheating,
the temperature sensing point should be positioned in the metal tool
not more than two cartridge diameters away. Cartridge heater
life is reduced by slow "on/off" cycling of power controllers. Slow
cycling occurs when the mass of metal to be heated is small and the cartridge
heater is rated higher than required for the application, or
with a highly sensitive temperature sensor. Full PID auto tuning
controllers with solid state relay output are recommended.
Integral thermocouple construction maintains the robust
qualities of the high power cartridge element and provides a very
responsive temperature sensing capability. This feature protects the
cartridge element against overheating when very rapid initial heating
and fast cycling is required.
Special Cartridge Heaters
Sealed (moistureproof) Cartridge Heaters
A common reason for cartridge heater
failure is the ingress of oil, moisture or plastic. To guard against
this, completely sealed elements are
recommended. With this design there is 20mm unheated at the lead end
which should not be subjected to temperatures above 200 cm?. It may be
advisable to leave at least 12mm of inactive length projecting from the
heated block. Sealed heating elements are protected at both ends to
prevent ingress of contaminating materials. The terminations should not
be immersed in fluids.
Total Immersion (waterproof) Cartridge Heaters
Where cartridge heaters are to be totally immersed in a fluid, please specify "waterproof" and the fitting required as there are a very
limited number of ways that waterproof cartridge heaters can be manufactured.
Hotco has an extensive range of stock cartridge heaters and also custom-make heaters to specific requirements. As always, If you need assistance in designing or selecting the right industrial heater for your application our team of technicians are available to assist.