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Mica Insulated Band Heaters

Bucan mica band heaters provide efficient and economical solutions to the heating requirements of many applications. With a sheath temperature that can go up to 900°F, various electrical termination styles, clamping mechanisms, and the ability to accommodate holes and cutouts, these heaters are successfully used in different industrial systems, but are mostly sought for in the plastics industry.

Characteristics of Mica Band Heater

Bucan mica band heaters are made with high-grade mica; the type and thickness of each mica insulating layer is carefully selected to provide excellent thermal conductivity and high dielectric strength. Similarly, to create a uniform heat distribution throughout the heater and to maintain the lowest possible resistive circuit temperature, an optimum combination of resistance ribbon alloy, cross-section and length is selected to design the resistance winding of each heater.

To maximize the surface-to-surface contact, Bucan mica band heaters are carefully rounded and formed to optimize the grip on a machine barrel. The external metallic protective sheath of the heater is made from a special alloy, which expands relatively less than when heated. The difference in thermal expansion makes the heater grip the barrel firmly once it is energized. This improves heat transfer which extends the life of the mica band heater.

Mica Band Heaters

Typical Heating Applications of Mica Band Heaters:

  • Injection Molding Machines
  • Plastic Extruders
  • Food Industry
  • Blow-Moulding Machines
  • Container Pipe & Tank Heating
  • Pharmaceutical Industry

Features of Mica Band Heaters

Watt density information

The durability and performance of a heater depends on selecting the appropriate wattage. Exceeding the maximum allowable watt density for the specified heater size will result in premature heater failure. While calculating watt densities, we should remove the area of the cold section from the overall calculated surface area of the heater.

Construction Cold Section
One piece 1" x width
Two piece 2" x width
Holes, Cutouts (Size + 1/2") x width

Points to consider while selecting watt density

  • Select narrower heaters where possible, as their heat transfer is superior to wide heaters. 1” to 2.5” wide heaters are ideal.
  • The watt density should be selected in accordance with the operating temperature. A table that shows the maximum allowable watt density is provided as a guideline.
  • To avoid short cycling and inefficient operation, select a wattage as close to the needed capacity as possible.
  • The wattage should be in accordance with the voltage and current rating of the controls.
  • The safe heating pattern of the material heated, thermal conductivity and coefficient of expansion of the cylinder are other factors that should be taken into consideration while deciding wattage.

Female receptacles and male plugs

16A-250V

25A-380V

10A-250V

10A-250V

Bucan band heaters are available with various types of electrical terminations. Each termination has its own unique characteristics, advantages and limitations. When selecting a termination style, the following factors must be taken into consideration: diameter, width, voltage, amperage, operating temperature, electrical safety and cost.

  • Screw terminals
  • Lead wire terminals
  • European plugs

Screw Terminals

Stainless steel screw terminals are the most convenient and economical means to connect a heater to an electrical power source. They are mostly recommended when high amperages (up to 25 amps) are involved. The temperature limitation is 840° F. Bucan offers different screw terminal styles.

  • Separate on opposite sides of gap (A)
  • Along the width side by side (B1)
  • Along the length side by side (B2)
  • With protective terminal box (G)
  • With ceramic protective cover (V)
Screw terminals Screw terminals Screw terminals

A Style   

Separate on opposite sides of the gap
Screws have 3/4" height above the barrel

B1 Style

Along the width side by side
Screws have 3/4" height above the barrel

B2 Style

Along the length side by side
Screws have 3/4" height above the barrel

 

Terminal Boxes "G" style

Terminal boxes eliminate the risk of electrical shock and electrical short by enclosing the terminals in a heavy-duty stainless steel box. Cover boxes come in two sizes, G1 and G2. For three-phase and dual voltage applications, special boxes are used.

 

W

L

H

G1

1 5/8"

2"

1 5/8"

G2

2"

1/4"

1 3/4

Ceramic terminal covers

 

Ceramic terminal covers "V" style

CCeramic terminal covers provide a cost effective means of reducing the risk of electrical shock and electrical shorts.

Ceramic terminal covers

Lead Wire Terminals

High temperature wire is internally connected to the heater. This provides a safer electrical connection. However, it is physically impossible to conceal heavy gauge wire under the top metallic sheet. This limits the maximum amperage applicable to 20 Amps. Bucan offers different lead wire termination styles. Within each style there are different models of lead wire exits.

  •  Armor cable

  • Stainless steel braid 

  • Plain lead wire

Within each style, there are different models of lead wire exits.

ARMOR CABLE

Armor cable provides the best protection against abrasion where a great deal of flexibility is not required. Straight lead exit or a 90° bend are the available options for this lead type. Brass fittings are used to secure the termination.

Armor cable straight Armor cable 90 degrees

H Style - straight lead exit

GM Style - 90° bend

 

STAINLESS STEEL BRAID

In applications where there is frequent movement or risk of abrasion, stainless steel braided leads are recommended. Heat shrink sleeving at the end of the leads prevents the braid from fraying.

Leads exit straight Low profile terminal cover Leads exit on each side of gap Leads exit 180 degrees from gap

E Style 
Straight lead exit

 LP Style
Low profile terminal cover

C Style
Used mostly with nozzle heaters

I Style
180° from gap

 

PLAIN LEAD WIRE

Plain leads are used where there is no risk of abrasion or contamination. High temperature wire with fiberglass insulation (840° F) is standard. Teflon insulated wire is also available.

Straight lead exit Leads exiting on both sides of the gap Leads exit on each side of gap 180 degrees from gap

EF Style
Straight lead exit

F Style 
Exiting on both sides of the gap

CF Style
Used mostly with nozzle heaters

IF Style
180° from gap

EUROPEAN PLUGS

European plugs are safe and simple to use. They provide a quick solution in applications where the electrical termination has to be disconnected frequently. They can be used on all our construction and clamping styles. EP terminals provide practical electrical connections when a failed heater has to be replaced. European plugs are available either with two round prongs (6 mm.) or three flat prongs (one of which is a ground).

Tangential European terminal box Vertical European terminal box European terminal box at 45 degree angle Three prong with ground European terminal box

K90 Style 
tangential box

K00 Style
vertical box

K45 Style
45° box

K3P Style 
3 Prong with ground

 

 

 

 

Maximum performance and ease of installation are two major considerations when selecting the construction style of a Bucan mica band heater. The following are the most common construction styles.

ONE PIECE
 

One-piece construction is used when a band heater can be installed on a barrel without extensively expanding it.
Diameter:5/8"min;22"max
Width: 5/8" min; 14" max

TWO PIECE OR MORE
 

Two or more pieces are for ease of installation for a mica heater. A practical choice when the barrel diameter is large.
Diameter:2"min;44"max Width: 5/8" min; 14" max

ONE PIECE FLEXIBLE
 

One-piece flexible mica heaters are used in applications where two-piece construction is not practical, and expanding the heater is necessary during installation. These heaters should not be opened more than twice.

PARTIAL
 

Partial band heaters are recommended where obstructions or complicated holes prevent having complete coverage on the surface of the barrel.

CONICAL 
 

Conical or irregular shaped mica heaters are made to fit unconventional forms. Heat transfer considerations impose limitations on the overall design and construction of these heaters. Our engineers are available to discuss the requirements of each application.

SQUARE AND RECTANGULAR 
 

Mica heaters can be made square, rectangular or multi-sided to suit your specific requirements.

REVERSE
 

Reverse mica heaters are used in applications where heating from inside the barrel is required. The outside shell of these heaters is the heating surface and all the terminations and clamps are located on the inside of the heater.
Diameter:3"min;36"max
Width: 1" min; 12" max

Clamping Mechanisms

The efficiency of heat transfer from a heater to the medium it is intended to heat is the most important factor that determines heater longevity. The quality of heat transfer from a mica band heater to the application surface, which is mostly through conduction, depends on the heater clamping mechanism.

Bucan mica band heaters come with different clamping styles. Each style has unique characteristics and advantages. Selection is based on the specific requirements of the application. For assistance in selecting the best available option, contact Bucan.

INDEPENDENT STRAP
 

These straps evenly distribute the drawing force around the band heater by clamping the heater tightly around the surface of the cylinder. This distributed force is transferred to the internal windings, improving heat transfer through effective surface contact and elimination of air gaps.

BUILT-IN BARREL NUTS
 

This clamping mechanism combines the drawing quality of an independent strap with ease of installation. The top sheet is transformed into a strap by incorporating barrel nut fasteners at both sides of the gap. Recommended when holes and cut-outs prevent the usage of an independent strap.

SPOT-WELDED STRAPS
 

This construction is similar to the built-in barrel nut style. The fastener section of an independent strap is spot welded on the top sheet on both sides of the gap. This construction allows for a heated section under the fastener.

FLANGE LOCK-UP
 

The most economical fastening style, flange lock-up is used mostly on narrow heaters.

WEDGE-LOCK
 

Low profile clamp. Used when clearance above the heater is limited. A wedge-like clamp slides on the lips of the heater located on both sides of the gap. The normal height from the inner diameter (ID) to the highest point of the wedge lock is 5/16”.

LATCH AND TRUNION
 

Ideal when fast detachment is required. The clamp is released with a flip of the thumb, eliminating the usage of any tools. The spring loaded 1/4-20 bolt absorbs thermal expansion in the fastened position.

HINGES
 

Used when a heater band has two sections. A piano hinge is incorporated on one side of the heater, while the other side can have any kind of clamp. The clearance between the two sections on the side of the hinge is 5/16“.

SPRING-LOADED BARREL NUTS
 

Independent straps, built-in barrel nuts and spot welded straps can have longer screws with incorporated die springs. These springs help to keep the band heater tight during thermal expansion. Only available in 1/4-20 screws.

CLAMPING PADS
 

Mostly used in two section partial heaters. When an obstruction prevents the usage of a complete band heater, it becomes necessary to create a large gap and fasten the heater to the cylinder on both sides of the gap. It is not advisable to have clamping pads on both sides of the same section of a heater, because thermal expansion might detach the heater from the cylinder.

REVERSE CLAMPING
 

This mechanism expands the diameter of a heater and is used with heaters that are made to heat the inside surface of a cylinder.

Installation tips OF MICA BAND HEATER

  • The cylinder should be clean from any contaminants and foreign materials.
  • The heater should be tightened firmly on the cylinder. The rims should be gently tapped with a plastic mallet and the heater re-tightened.
  • Energize the heater for a short period of time and then re-tighten the fasteners.
  • To compensate for thermal expansion, large diameter heaters should have spring-loaded fasteners.
  • One-piece construction heaters should be opened only slightly, and made to slide on a cylinder. Two-piece construction or flexible heaters should be used when a heater has to be fully opened.