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Mica Band Heaters

Thermal designs and manufactures Mica band heaters, Ceramic heater bands, and Nozzle band heaters. Each mica band heater is manufactured to your specifications and can be shipped as quickly as many off the shelf heaters when needed. Mica band heaters are used to heat cylinders such as the barrels and nozzles of plastic injection and extruding machines.

Advantages of Mica Heater Bands:


  • High watt-density capabilities
  • Reasonably high temperature capabilities 900 degrees F (900 degrees)
  • Good efficiency
  • Good lifetime 
  • Low cost

It’s really pretty simple, after locating a mica band heaters configuration from our config page or from the config PDF located in the sidebar, determine the diameter of the part you want to install the heater on.


mica band heaters


Hopefully, you can get this information from a drawing, but if not, you can refer to the above graphic and easily make your own measurement (We only need one of the dimensions).  Next, determine the width of the heater and the length of the lead wire if appropriate.

After that, specify the wattage and the available voltage and you are ready to go!  If there are holes or notches in your band heater click here for more information on how to measure your mica band heaters.

Band Heater Specifications
Width± 1/16″
Finished Diameter± 1/32″
Wattage at Design Voltage+5% – 10%
Standard Gap Size for 1 Piece Heater5/16″
Standard Gap Size for 2 Piece Heater3/16″
Standard Terminal Height13/16″
Low Profile Standard Terminal Height3/8″


Check Your Barrel or Nozzle Surfaces

When replacing a mica band heater assure that the barrel or nozzle is free of material, smooth and clean.

mica heater bands

A rough spot or foreign material on the barrel can greatly reduce the life of your mica band heater.  A small particle can leave an air gap on either side of itself which can cause a “hot spot.”

Air will not conduct the heat away from your heater as fast as the metal of the barrel.  This results in a spot on the heater where the temperature will be significantly hotter than the rest of the heater.  Just a 0.005″ air gap on a typical 30 watts per square inch heater will cause that spot to run 250 degrees (F) hotter!


The Tighter, The Better

After installing a new mica band heater, we suggest that you come back to it after fifteen minutes of operating time.  After proper actions are taken to assure there is no power going to the heater and that the heater will not cycle on, re-tighten your straps or clamping mechanism.

Make a habit of checking the tightness of the band heater periodically and you will be surprised at how you can increase the life of your band heaters.


Fewer Holes, Longer Life

Every time you add a hole to a mica band heater, you give another avenue for Contaminants to enter the heater.  You also add expense and often add to the delivery time.

If the hole is for a thermocouple or other instrument, you can often order a heater with a larger gap to accommodate the thermocouple.  Another option if the band heater has several holes along the circumference of the heater is to use two heaters instead of one.  For instance if you are using a six inch wide heater with several one inch holes, you might try using two heaters that are 2.5″ wide.

Call us at 1-800-633-2962 and speak with one of our customer service reps or email us at if you’d like some help in trouble-shooting your mica band heaters problems.


Use the Right Parts

If your mica band heaters has post terminals, make sure you are using high temperature ring terminals.  Standard ring terminals will cook to the point they become brittle and can easily break causing a short.  You can find high temperature wire and ring terminals here.

If your mica heater bands or strip heater terminations are not covered with a terminal box, consider using ceramic terminal covers.  Dust, material or other contaminates can build quickly on and around the connections eventually carbonizing which will short the mica heater bands and cause downtime.


From our FAQ’s

What is watt density and how is it related to heater life?

Watt density is a measure of the rate of heat being transferred through the surface of the heater. That is, if you were to draw a 1”x1” square on the surface of the heater, how much heat would need to pass through that 1 square inch area. This is called watt density and it is measured as watts per square inch. Other things being equal, the higher the watt density, the higher the temperature inside the heater. As the temperature inside the heater increases, the materials inside the heater are operating closer to their breaking point resulting in shorter heater life. Generally, for satisfactory life in a mica band heater, the watt density should be less than 50 watts per square inch for heater diameters less than 3 inches, less that 40 watts per square inch for band heaters with diameters between 3 and 6 inches and less than 35 watts per square inch for mica bands with diameters between 6 and 10 inches. For cartridge heaters, the watt density should be less than 200 watts per square inch. For ceramic knuckle band heaters, the watt density should be less than 35 watts per square inch. Also, higher operating temperatures require lower watt density for equivalent temperatures inside the heater and equivalent heater life.