Band heaters and ring heaters

What is a band heater and what is it used for

A band heater (also called a ring heater, clamp heater, or collar heater — abbreviated HN) is a device designed to heat cylindrical surfaces from the outside. Its key advantage is ease of installation: no additional mounting hardware is required on the equipment — the heater simply slides over the pipe, screw or barrel and is tightened with screws.

Inside the stainless or galvanised steel housing (0.25–0.5 mm thick) sits the resistance element — a nichrome wire or strip insulated by mica sheets or ceramic segments. The housing is formed into a ring which, when installed, tightly clamps the heated surface for maximum heat transfer and uniform heating.

Within the ring heater family, half-clamp heaters (half-band heater) are a separate category — used when installation over the end of a cylinder is not possible. Half-clamp elements are bolted together at the joint to form a split ring. For large diameters (above 380 mm) the full ring can be built from three or more segments, each mounted individually.

Mica band heaters

Mica ring and half-ring heaters have a relatively rigid structure. After packing the insulating layers into the metal housing, the blank is rolled to the required diameter — creating a compression of the materials. This process is irreversible: any attempt to significantly "open" the finished ring damages the internal layers and causes a short circuit. If the heater must be fitted over the side of a cylinder (rather than from the end), order half-band heater — the half-clamp version.

Installation of mica band heater and half-band heaters must be carried out on a clean, prepared surface. After the first heat cycle, the clamping screws must be re-tightened — this closes the gap created by thermal expansion. Any sag in the heater is unacceptable: local overheating in that zone will cause premature failure within the first days of operation.

Economic argument for half-band heater over band heater: a half-clamp costs less than a full ring, so replacement is cheaper. Also, if one half fails, the other continues to work — replacement takes only a few minutes of downtime.

Power density of mica heaters is limited to 4 W/cm² — above this, the insulation burns through. With correct installation and adequate heat dissipation, any mica clamp is well within these limits. Size range: minimum inner diameter 30 mm, maximum 380 mm (larger on request). Width can be almost any value, but not more than 2× the diameter, otherwise heating surface quality suffers.

Heaters can be manufactured with holes, cutouts and additional mounting features — all to customer drawing.

Ceramic ring heaters

A ceramic clamp heater consists of a strip of ceramic segments with a nichrome coil inside. The segments have mating lugs and slots — they can pivot relative to each other in one plane, allowing the strip to be wrapped into a ring of any diameter. A stainless steel clamp housing holds it on the cylindrical surface.

Ceramic heaters have no rigid structure — they can be stretched open and fitted over the side of a surface rather than from the end. Installation requirements are less strict than for mica types, but contamination and surface irregularities must still be avoided, as they damage the ceramic segments during tightening.

In terms of power, ceramic heaters are nearly twice as powerful as mica — up to 8 W/cm². Maximum temperature is 750 °C. Minimum inner diameter 50 mm, minimum width 15 mm. Maximum dimensions are limited only by production complexity.

Nozzle heaters for injection moulding machines

A separate sub-group — nozzle heaters. Used on injection moulding machine nozzles where temperature exceeds 300 °C and higher specific power is needed. The main difference from standard mica clamps is a higher power density of up to 7 W/cm² at the same diameter. This is achieved by special processing and swaging of the housing: the internal fill is compressed more tightly, so heat is transferred more efficiently without risk of burnout.

Nozzle heaters are manufactured in a sealed construction — molten plastic cannot reach the live parts. In almost all cases they are supplied with a one-metre heat-resistant lead in protective metal braid, clamped to the heater with a metal ferrule.

Standard size range: from 25 mm diameter × 20 mm width up to 100 mm diameter × 60 mm width. Larger sizes on request. Power depends on size; standard voltage is 230 V.

Cast clamp heaters

The design is straightforward but production-intensive. Manufacture requires a tubular heater plus a casting facility. A tubular heater is placed in a split mould and cast in aluminium or brass. The non-ferrous metal volume and casting complexity make cast clamp heaters noticeably more expensive than mica types — but they win on strength and thermal mass.

Cast clamps are used where stable heating is required under variable loads, or in high-vibration environments — for example, on presses and heavy-duty extruders.

Silicone heaters

Silicone is a flexible material, so silicone heaters are used to heat both flat and cylindrical surfaces. For installation on a barrel or pipe, hooks are attached at the ends and a spring is tensioned between them — this presses the heater against the surface.

This is a relatively new product that has not yet been widely adopted: manufacturing is expensive and specific power is limited to 3 W/cm². However, for certain applications (heating of static vessels, anti-icing, laboratory water baths (bain-maries)) it is the optimum choice.

Installation and mounting

Screw fasteners at the ends of the clamp heater follow the "hose clamp" principle: the ends are drawn together with bolts. Half-clamp heaters (half-band heater) are bolted at the joint between the two halves.

For non-standard situations where bolt fastening is not possible, the fixing method is agreed upon individually: welded pressure plates, tension springs, or dedicated locking clamps.

A critical step — re-tightening after the first heat cycle. During initial heating the housing material expands and a gap appears between the heater and the surface. If the bolts are not re-tightened within the first hour of operation, the heater will overheat unevenly, reducing service life from the normal 3–5 years to as little as 3–6 months.

Order worldwide

Custom-manufactured to drawing — from 3 days, from 1 piece. Worldwide shipping via DHL, FedEx, SDEK. 1-year warranty on all products. In business since 2010. To order, Send us a sketch, a photo of an existing heater, or describe your requirements — we will work out the specifications and provide a price within 15 minutes during business hours.

Certification: GOST 13268-88, on request — DIN, IEC, ASTM. TEN-Miass, ul. Shota Rustaveli 82a, Tashkent, Uzbekistan 100000. Phone: +998 50 090 19 24.