A stack-type furnace used for melting of metals, consisting of, but not limited to, furnace proper, tuyeres, fans or blowers, tapping spout, charging equipment, gas cleaning devices and other auxiliaries.

A furnace in which the melting and refining of metal is accomplished by the application of heat to a saucer type or shallow hearth in an enclosed chamber. Such furnace consists of, but is not limited to, the furnace proper, checkers, flues and stack and may include a waste heat boiler, and oxygen lance and other auxiliaries pertinent to the process.

Any foundry where operations run intermittently for just long enough at one time to pour the molds that are ready on the foundry floor, job by job.

The time in which the metal is melting and available at the spout or tap hole, excluding any time the equipment is idle, preheating or preparing for shut down.

Any foundry where operations will run continuously to pour a succession of molds that are constantly being prepared to receive the continuous flow of iron, or any foundry where the process weight will exceed 50,000 lb/hr, or any operation where melt times are in excess of four hours per 24-hour period.