Powder coating utility poles takes infrared plus convection heat.

Combination gas-fired radiant/convection systems couple direct radiant heat with a convection zone. Convection heating is especially effective for use on parts with a relatively small diameter and substantial length such as utility poles.

United Lighting Standards, Warren, Michigan, manufactures steel and aluminum lighting poles and related products in lengths ranging from 10 to 40 feet and wall thicknesses from one-eighth to one-half inch. The company switched from liquid solvent based paints to powder coatings in 1987, curing and drying the products in an electric infrared furnace.

Over the years, a number of system problems became evident, including insufficient curing of large, light colored products, and frequent shutdown of the line for maintenance and element replacement. Electric element replacement also generated a hefty expense of at least $10,000 annually.

To eliminate these problems, company management decided on a combination infrared and convection oven designed and fabricated by Thermovation Engineering of Cleveland. Thermovation fabricated a free-standing unit measuring 32 feet in length, eight feet high and five feet wide, with a maximum capacity of 2 million Btu/hr., sufficient for the company to easily reach its increased production goals. Heavy cast-iron premix burners were specified for extended life and more precise heat modulation.

Digital temperature controllers in each zone of the oven modulate fuel input to the burners; a non-contact heat sensor measures product temperature at the oven's exit. The entire system was tested and debugged at the Thermovation factory, enabling it to be fully installed and operational at the customer's facility in just six days.

Based on United Lighting Standard's production schedule, the new oven could save the firm more than $100,000 annually in reduced energy costs. Improved productivity and lower maintenance are important side benefits. "The number of poles we can put through the system per shift is up by at least 30 percent, "comments Bernie Jenkins, United's general manager, "and we're confident we can easily raise it to 50 or 60 percent. Also, the excess capacity of the system will allow us to significantly raise throughput without any major system redesign or renovation."