Cartridge Heaters

Cartridge Heaters

Cartridge heaters are high-density heating cells that have their nickel chrome heating cores positioned internally as close as possible to the outside shell. The specially formulated MgO electrical insulating medium utilized inside a cartridge heater is transformed into a rock-hard, highly efficient heat transferring medium through a special cold forming process.

Cartridge heaters can withstand tough industrial usage; they can transmit up to 200 watts/in² heating capacity and are able to attain up to 1500°F sheath temperature. In order to facilitate installation and heat transmission, cartridge heaters are made 0.004 inches less than the nominal size of the receptacle hole, with a tolerance of +/- 0.002 in. Standard Bucan cartridge heaters are supplied with electrical leads that are connected internally within a 3/8 inch cold section. In excessively hot applications, the length of this cold section could be increased.

Cartridge heaters can be dual-voltage, three-phase, and/or supplied with a ground terminal. With ten different termination styles, mounting attachments and various optional features, Bucan high-density cartridge heaters are widely used in numerous high temperature industrial applications. Here are some examples:

INDUSTRIAL APPLICATIONS

PLASTIC MOLDINGS

PACKAGING EQUIPMENT

HEATING TANKS

PLASTIC EXTRUDERS

LABELLING MACHINERY

AIR AND LIQUID HEATING

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 WATTAGE 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"

Built-in thermocouples

Cartridge heaters can have built-in "J" or "K" type thermocouples that could be grounded or ungrounded. These thermocouples can be installed at the disc end or the middle of a cartridge heater.

 

Graphite coating

Cartridge heaters are easier to install and remove from receptacle holes if they are coated with a graphite-like solid lubricant. This material does not increase the outside diameter of the cartridge heater, and is suitable for temperatures up to 750° F.

 

Moisture and contamination proofing

Cartridge heaters can be protected against moisture and contamination by adding Teflon lead wires and sealing the end of the cartridge heater using epoxy, RTV silicone or Teflon. The temperature limitation is 480° F.

 

Distributed wattage

Cartridge heaters used 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, cartridge heaters could be made to have higher wattages at the ends. 35/30/35 is a common wattage distribution.

 

Center-less grinding

Cartridge heaters which are to be used 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

Cartridge heaters can also be manufactured with cold sections and separate zones that can be controlled independently.

Selection and Installation Tips

  • Cartridge 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 on a low voltage prior to usage, in order to eliminate possible moisture contamination. It is always preferable to stock cartridges in sealed bags.
  • Cartridge heaters 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 heater.
  • 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 heaters.
  • Watt densities should be kept within the safe range. This can be done by using either larger cartridge heaters or as many as it is reasonably possible.
  • To prevent short cycling, the wattage of a cartridge heater should be close to the wattage required by that specific application.

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.

Heater Diameter NPT Size
1/4" 1/8" - 27
3/8" 1/4" - 18
1/2" 3/8" - 18
5/8" 1/2" - 14
3/4" 3/4" - 14

IM Style: 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.

 

 

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

To provide flexibility at the lead end, high temperature (840°F) leads are connected to the solid pins inside the cartridge.

Stainless steel braided leads connected straight to cartridge heater

Stainless Steel braided leads connected straight

K1 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.

Teflon leads connected straight ot cartridge heater

Teflon insulated leads connected straight

TF 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).

Armor cable leads connected straight or cartridge heater

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 brazed or crimped to the cartridge. 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 1” extended solid pins of a cartridge. These types of terminals are 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 braids, but provide contamination resistance in addition to superior protection against abrasion. A copper elbow braised to the cartridge externally provides 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"