High Density Cartridge Heaters

Applications Of Cartridge Heater

• PLASTIC MOLDINGS
• PACKAGING EQUIPMENT
• HEATING TANKS
• PLASTIC EXTRUDERS
• LABELLING MACHINERY
• AIR AND LIQUID HEATING

Specifications Of Cartridge Heater

• Cartridges heaters should have a tight fit in the receptacle hole. Drilling and reaming to the next standard size and using a larger cartridge could solve the problem of loose or worn-out holes.
• Lead wires should be kept away from abrasion and should not be exposed to temperatures above 840°F.
• Stocked cartridge heaters, which have been exposed to air and moisture for a long period of time, should be energized at a low voltage prior to usage, in order to eliminate possible moisture contamination. It is always preferable to stock cartridges in sealed bags.
• Cartridges should be immersed completely inside the receptacle hole. Proper mounting attachments can prevent their edging out by vibration. If it is necessary to have an exposed section, that part should be unheated
• Receptacle holes should be properly cleaned prior to the installation of a cartridge.
• When designing molds, it is recommended to make the receptacle cavities such that they will accommodate cartridge heaters completely and all-the-way-through. This will later facilitate the removal of the heaters.
• Watt densities should be kept within the safe range. This can be done by using either larger cartridges or as many as it is reasonably possible.
• To prevent short cycling, the wattage of a cartridge heater should be close to the required application wattage.

Mounting Attachments

Electrical Terminations

High Temperature Leads externally connected A1 Style High temperature (840°F) fiberglass insulated leads are connected externally to the two solid pins exiting from the cartridge. A silicone impregnated fiberglass jacket insulates the connection.	High Temperature Leads internally connected A2 Style To provide flexibility at the lead end, high temperature (840°F) leads are connected to the solid pins inside the cartridge.
High Temperature leads connected at 90 degrees angle A3 Style A bracket having the same diameter as the cartridge provides a 90° exit to the fiberglass insulated high temperature leads. The bracket is potted with high temperature cement (480°F).	Stainless Steel leads connected at 90 degrees angle K2 Style
Stainless Steel braided leads connected straight K1 Style High temperature leads (840°F), with flexible abrasion resistant stainless steel braid exit straight from a cartridge. An additional 1/4” cold section from the immersed length is allocated to accommodate the stainless steel jacket.	Teflon insulated leads connected straight TF Style Internally connected Teflon leads (480°F), with Teflon plugs, protect the cartridge from contamination. High temperature black epoxy or silicone RTV seals are available too. A minimum cold section of 1” at the lead end is necessary to protect the Teflon leads from high temperature.
Armor Cable Stainless Steel leads connected straight X1 Style High temperature (840°F) lead wires with abrasion and contamination resistant armor cable protection exit straight from a cartridge heater. The armor cable is crimped to the cartridge (brazing is available upon request). In order to accommodate the armor cable, an additional 1/4” cold section is allocated at the lead end.	Screw Terminals PT Style For high temperature applications, screw terminals (#10-32 is standard, other sizes are available) are silver-brazed to the extended solid pins of a cartridge. This type of terminal is not recommended for cartridges having less than 1/2” diameter
Armor Cable Stainless Steel leads connected at 90 degrees with Copper elbow X3 Style Armor cables are less flexible than stainless steel braid, but provide contamination resistance in addition to superior protection against abrasion. A copper elbow, brazed to the cartridge externally, provides a 90° transfer.	Armor Cable Stainless Steel leads connected at 90 degrees angle X2 Style Protective armor cable, which is silver brazed to the side of a low profile stainless steel bracket, provides right-angle transfer to the high temperature leads when space is limited and elbows cannot be used.

90° bracket and elbow heights

Operating temperature versus actual temperature of cartridge

Bucan cartridge heaters are designed to withstand a sheath temperature of up to 1500°F. The recommended maximum operating temperatures for many applications are much less than that. There are many factors that have a direct effect on the lag between the actual sheath temperature of a cartridge heater and the monitored temperature of the surrounding material during the heat-up cycle. In some cases, this temperature lag is so significant that the cartridge will reach its elevated critical temperature even when the surrounding material is monitored to have a relatively much lower temperature level. The most common factors that contribute to the degree of temperature difference are the following:

• Thermal conductivity of the material being heated
• The cartridge sheath watt density
• The tightness of the cartridge inside the hole
• The location of the monitoring sensor
• The alloy of the cartridge sheath material
• Contamination around the cartridge heater

These factors should be taken into consideration while selecting a cartridge for a specific application. One common practice is to use stainless steel cartridge sheathes for temperatures up to 1000°F and Incoloy sheathes for temperatures up to 1400°F. Another design consideration related to the operating temperature is the electrical termination of a cartridge. Teflon and TGGT leads have 480°F rating while MGT wires can withstand up to 840°F. When cartridges are used at relatively high temperatures, the terminals selected should be either different than the common high temperature lead wires; or the design should be such that the temperature around the lead wires (whether the leads are connected internally or externally to the cartridge) is maintained at a temperature level lower than the critical temperature limit of the lead wire.

Built-in thermocouples

One optional feature on Bucan cartridges is built-in thermocouples. These could be type "J" or "K", grounded or ungrounded, and attached either at the disc end or the middle of the cartridge.

Graphite coating

To facilitate their installation and removal, cartridges can be coated with a graphite-like substance. This solid lubricant does not increase the outside diameter, and is suitable for temperatures up to 750°F.

Moisture and contamination resisting seals

To protect cartridge heaters against moisture and contamination, Teflon lead wires with Teflon seals are used. Epoxy (250°F) or RTV (450°F) silicone seals are alternative contamination and moisture resisting barriers.

Distributed wattage

In applications such as sealing bars or rubber molds, the two ends of a cartridge heater are usually colder than the middle. To overcome this inconsistency and have a uniformly distributed heat source, cartridges could be made to have higher wattages at the ends. 35/30/35 is a common wattage distribution.

Center-less grinding

In applications where superior heat transfer is required, the tolerance on the outside diameter could be improved to +/-0.001" by center-less grinding.

Zones and cold sections

We can also manufacture cartridges with cold sections and separate zones that can be controlled independently.