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A new way to heat and cool the barrels of plastics processing machines was launched at NPE 2003 by Insul-Vest Inc. New Insul-Watt heaters use a combination of radiant infrared heating, thick ceramic insulation, and forced-air cooling to heat faster with less energy, greater safety, and a more comfortable working environment. Although the new heaters cost more than conventional heater bands, operating costs are said to be lower due to energy savings and longer service life, estimated at five years vs. one to two years for heater bands. Payback on investment is put at 12 to 18 months.

“Processors who heat and cool any barrel stand to benefit,” declares Gordon Pendergraft, Insul-Vest’s president, adding that beneficiaries could include injection molders, blow molders, extruders, and compounders.

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Insul-Watt utilizes no new technology, but a combination not previously used for plastics:

• Infrared heating elements generate radiant energy, which is said to be faster-acting and more efficient than conductive heat. The heater elements reach their typical operating temperature of 1100 F in 15 sec.
• Heater elements are embedded in the underside of sections of vacuum-cast ceramic-fiber insulation, which reduces heat escape to the plant floor, thereby increasing worker comfort and reducing the cost of plant air conditioning. While operating, the outside of the insulation is just warm to the touch. The insulated heater modules cover 100% of the barrel’s surface (unlike standard heaters). Prewired sections are held together by stainless-steel, Velcro-style fasteners. (Unlike with heater bands, processors need not be concerned about obtaining a tight fit around the barrel to prevent heater burn-out.)
• IR elements are offset from the barrel by 0.375 in. to leave space for vacuum cooling. An optional vacuum ring can be placed between each heating module. Each Insul-Watt module constitutes a temperature zone that can have its own cooling-air inlets and outlets.
• Closed-loop heating-cooling controls from Watlow reportedly hold barrel-temperature variation within 1° F. 

More efficient operation

Insul-Watt’s energy efficiency is around 90%, versus about 50% for most existing heaters, Pendergraft says. He pegs overall energy savings at around 50%. This is due to both the insulation and rapid ramp-up and ramp-down, which cuts time heaters need to be operating.

Moreover, heat distribution in the barrel is claimed to be more uniform and consistent than with heater bands. Pendergraft says that translates into fewer hot and cold spots.

Insul-Watt heaters are being tested by a Tier 1 automotive molder and by Kansas Plastics, a custom molder in Wellington, Kan. The latter is using a prototype heating-cooling system on the barrel of a 700-ton press. “Results are promising,” declares Dick Bloomer, president of Kansas Plastics. He says heater response times are shorter and energy efficiency has been significantly improved.