Mineral Insulated (MI) Band Heaters

Mineral Insulated (MI) Band Heaters
The MI band heater from Watlow® is a high-performance heater. The band heater's performance and name are derived from Watlow's exclusive mineral insulation—a material with much higher thermal conductivity than mica and hard ceramic insulators used in conventional heaters.

A thin layer of the “high” thermally conductive MI material is used to electrically insulate the element wire from the inside diameter of the heater sheath. A thicker, “low” thermally conductive layer backs up the element wire directing the heat inward toward the part being heated.

The result is more efficient heat transfer, which lowers element wire temperatures and increases band heater life.

Performance Capabilities

  • Heater operating temperatures up to 1400°F (760°C)
  • Watt densities up to 100 W/in2 (15.5 W/cm2) available on large diameter barrel bands
  • Maximum voltage to 480V

Typical Applications

  • Extruders
  • Blown film dies
  • Injection molding machines
  • Other cylinder heating applications

Features and Benefits

  • High thermal conductivity of MI and low mass construction provides rapid response to temperature control and avoids thermal lag
  • Operating temperatures up to 1400°F (760°C) allows safe melting of resins such as PEEK™, Teflon®, Ultem® and Zytel®
  • Higher watt densities contribute to faster heat-up and throughput for increased productivity
  • Stainless steel cover and side fold design resists contamination from overflow of plastic or other free-flowing materials
  • Attached clamp bars eliminates cumbersome clamping straps, making installation easier



Lead Wire

Heaters rated at less than 250VAC use UL® approved lead insulation for operations up to 480°F (250°C) as standard. Lead insulation UL® rated for operation to 840°F (450°C) is available for high-temperature applications where leads are shrouded or enclosed with the heater. These leads are available in any of the Type B variations with loose braid and Types E, F and H lead configurations. All heaters rated at more than 250VAC use this wire. When ordering, specify 850°F (450°C) wire.



ASTM Type J or K thermocouples are available on lead Type B with loose braid and fiberglass sleeving. They are also available on E, F and H leads. The thermocouple junction, spot-welded to the heater sheath, provides a signal for measuring relative heater temperature. A separate thermocouple is available.
Heavy Duty Strain Relief

Heavy Duty Strain Relief

Heavy duty strain relief is recommended for applications where there is great stress or continued flexing of the leads. The strain relief is available on Type B, Type B - 90° and Type B - 180° leads only. To order, specify heavy-duty strain relief. Note: not available with loose braid or fiberglass sleeving.

Expandable Heaters with Post Terminals or Leads

Expandable Heaters with Post Terminals or Leads

Expandable heaters are two-piece units with a common top metal that allow the heater to expand to the full diameter of the barrel. On expandable bands, each half will comprise one-half of the total wattage. On both expandable and two-piece bands, each half is rated at full operating voltage, unless otherwise specified. Post terminals for MI band heaters 11⁄2 in. (38mm) wide or greater are located next to the expansion joint. Leads may be located anywhere along the circumference except near the gap and at the expansion joint. Two sets of leads are required. On 1 in. (25 mm) wide MI band heaters, post terminals are located 90° from the expansion joint. Leads may be located anywhere along the circumference except near the gap and at the expansion joint. Two sets of leads are required. To order, specify expandable. Expandable heaters are designed to be opened for new installation only.

Metallic Terminal Box

Metallic Terminal Box

Metallic terminal boxes are available from stock on 3½” inside diameter x 1½” wide (89 mm x 38 mm) or larger heaters. Terminal boxes attach directly to the heater and act as a safety feature by covering the terminals. The conduit may be attached to the box through 7⁄8 in. (22.2 mm) diameter holes in the ends of the box. Two-piece heaters require two boxes. To order, specify terminal box.


MI band heaters with holes are available on all widths except 1 in. (25 mm) wide. Contact your Watlow representative for hole sizes and location constraints. To order, specify hole size and location. The inside diameter minimum is 3 in. (76 mm).
Download the Mineral Insulated Band Heater Datasheet


Hands-On Assistance from Technical Specialists

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