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High Density Cartridge Heaters

In high-density cartridge heaters, the resistance wire loops are positioned as close as possible to the outside shell. Because the MgO powder insulation around these loops is compacted by swaging and transformed into a very hard medium, heat transmission is very efficient. Bucan cartridges can have up to 200 w/in2 watt densities.

Bucan Cartridge heaters are usually supplied with lead wires. The attachment of the leads to the central pins is done internally, in a 3/8" cold section. In excessively hot applications, the length of this cold section can be increased. To facilitate installation and avoid excessive air pockets, cartridges are made 0.004" smaller than the nominal size of the receptacle hole with a tolerance of +/-0.002". Bucan cartridges can be dual-voltage, three-phase, and/or be supplied with ground terminals.

With ten different termination styles, mounting attachments and various optional features, Bucan high-density cartridges heaters are widely used in numerous high temperature applications.

Cartridge Heaters

Applications Of Cartridge Heater

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

Specifications Of Cartridge Heater

DIAMETER (NOM) 1/4" 5/16" 3/8" 1/2" 5/8" 3/4" 1"
DIAMETER (ACTUAL) 0.246 0.310 0.371 0.496 0.621 0.746 0.996
MAX LENGTH 36" 36" 72" 96" 96" 96" 96"
MAX VOLTAGE CSA 240V 240V 480V 480V 480V 480V 480V
MAX VOLTAGE 250V 250V 600V 600V 600V 600V 600V
MAX WATTS AT 240V 1200W 1300W 2000W 3000W 5300W 5300W 5300W
WATTAGE TOLERANCE +5% -10%
DIAMETER TOLERANCE +/- 0.002"
LENGTH TOLERANCE +/-2% OF LENGTH
CAMBER TOLERANCE 0.010" PER FT UP TO 12"
  0.018" PER FT ABOVE 12"

SELECTION & INSTALLATION OF CARTRIDGES HEATERS 

  • 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

FL Style

 

Flange mounting attachments secure the cartridge firmly in place in applications where there is excessive vibration. 1 ½”diameter is the standard flange size. Flanges with smaller diameters are generally used as stop rings.

IM Style

Cartridge Diameter NPT Size *Single Ended
Fitting Length
*Double Ended
Fitting Length
1/4" 1/8" - 27 0.56 1
3/8" 1/4" - 18 0.68 1.13
1/2" 3/8" - 18 0.75 1.25
5/8" 1/2" - 14 0.88 1.75
3/4" 3/4" - 14 1.03 1.85


The conical thread of NPT fittings (single or double ended), allow for simultaneous threading and sealing. Brass or stainless steel fittings can be brazed on the lead end of a cartridge heater.

Electrical Terminations

High temperature lead wires externally connected to cartridge heater

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 lead wires internally connected to cartridge heater

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

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 braided leads connected at 90 degrees to cartridge heater

Stainless Steel leads connected at 90 degrees angle

K2 Style

 

Stainless steel braided leads connected straight to cartridge heater

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 leads connected straight ot cartridge heater

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 externally connected to cartridge heater

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 leads connected at 90 degrees copper elbow

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 leads connected at 90 degrees silver brazed

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

Cartridge OD Bracket Elbow
1/4" 3/8" 7/8"
5/16" 3/8" 1"
3/8" 3/8" 1"
1/2" 1/2" 1 3/16"
5/8" 5/8" 1 3/8"
3/4" 5/8" 2"

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.