The state of the cupola.

"Why melt cupola?" asked Francis Kaiser, Modern Equipment Co., Port Washington, Wisconsin. "It is the best available technology to assure you of high quality, low cost iron. Time has proven [melting cupola] is a wise thing to do."

Apparently, many in the industry agree. Kaiser estimates that cupola melted iron will account for 63-64% of all the castings poured in the U.S. this year.

Through a program touching on every aspect of design, materials and operation, the AFS International Cupola Conference presented a facet of the metalcasting industry that is still vibrant and very much alive. Held March 1-3 in Rosemont, Illinois, the first AFS conference dedicated to the cupola in 14 years attracted more than 200 foundrymen and featured technical presentations by 26 authors.

Rethinking the Options

In his leadoff presentation, Kaiser briefly recounted the long history of the cupola--from its appearance in England in 1794 to the inception of electric melters and the subsequent decline in cupola use. The change to electric melting in the late 1950s resulted from the belief that it offered a clean, low-cost alternative to the seemingly dirty and inexact art of the cupola.

Today, however, he said, "environmental compliance needs are catching up with electric melting processes." Many foundries with electric furnaces have had to install afterburner systems run on purchased fuels to maintain the steady high-temperature conditions required for the combustion of exhaust gas hydrocarbons. Conversely, cupolas reuse the carbon monoxide given off in the process to achieve this combustion.

Another surprise, Kaiser said, is that the cupola can be far more economical to use. Using standard cost estimates for fuel, he determined that the total energy cost per ton of castings for an efficiently run cupola is $18.65, compared to $34.73 for electric melting.

Extended Heats

More often than not, efficient cupola operation today means running extended heats. According to Patrick Frederick, Auburn Foundry, Auburn, Indiana, extended heats enable the foundry to tap continuously for two weeks or more with only brief shutdowns during weekends to make minor repairs.

These long campaigns maximize the environmental advantages of cupolas and the excellent emission control systems that have been introduced for them in the last decade. The charging process is greatly simplified and the need for more than one unit is reduced.

To achieve the benefits of longer production periods, reduced tap downtime and lower safety risks associated with bottom drop, special care must be taken with the operations. Experienced personnel operating from established, written procedures are vital to effective campaigns.

The foundry must have large holding furnace capacity and proper cupola refractories are crucial. Above all, Frederick stressed, the key to success with extended heats is an even, constant heat level. "Pace it, don't push it," he said.

Environmental Concerns

Despite the cupola's favorable comparisons to electric melting, the process, like almost every aspect of the industry, faces heavy environmental regulation from the EPA and state agencies. Cupola melters are finding it increasingly difficult to continue in established production and disposal patterns. Comparing the proceedings from the recent conference to those of the 1980 gathering illustrates the ever-growing body of environmental research in the industry and the increasing regulation that must be addressed.

To that end, five of the presentations dealt directly with environmental issues, while almost all were at least in some way concerned with the issue. To lead off the environmental session, Christel Ackerman, Intermet Foundries, Inc., Lynchburg, Virginia, advised cupola melters of the best ways to assure fair, responsible environmental compliance conditions.

The keys to navigating through the red tape are technical preparation, an understanding of all pertinent regulations and meticulous documentation of any contact with regulatory agencies, she said.

Other papers focused on the treatment and recycling of cupola by-products like wastewater, ashes, dust and coke fines, and slag. An update on the coke industry, hard hit by the Clean Air Act, detailed the impact of massive compliance costs on the price of the primary cupola fuel.