Retort furnace

The Philadelphia Mint recently began a round of upgrades for its heat treat furnaces. Their function in the minting process is to anneal, clean, and dry the coin blanks to soften the metal prior to striking into coins, extending the service life of the striking dies.

SECO/WARWICK Group’s American subsidiary, located in Meadville, PA, recently began upgrades, a refurbishment of all five of the Philadelphia Mint’s heat-treating furnaces, one furnace per year. The heat-treating furnaces were originally installed there by SECO/WARWICK USA from 1994 through 2000.

All five furnaces are 4000 pound per hour rotary retort furnaces outfitted with a quench system, as well as a hopper feeder, a batch burnish barrel, and a batch/continuous drum drier. The furnaces are showing their age after a quarter century, so rather than nickel and dime the maintenance, the mint opted for a comprehensive refurbishment.

“Our Partner has plenty of coin to heat-treat, but they don’t have any to burn," commented Marcus Lord, managing director at SECO/WARWICK USA. "These waste-heat recovery and combustion efficiency upgrades are going to save them a mint while cutting carbon and NOx emissions nearly in half."

To reduce energy consumption, the Mint is replacing insulation, roof panels, and radiant tubes as well as upgrading the loading systems. More energy efficient burners are being installed, along with recuperators to preheat the combustion air, to improve energy efficiency and use less natural gas. Mechanical improvements include replacing drive motors and two-speed gear boxes. The retort can over-heat and warp if the rotary retort unexpectedly stops before the cool-down cycle. As a failsafe, SECO/WARWICK added a pneumatic backup motor that can run the gear box off the Mint’s compressed air reservoir during a power outage.

The mint was established by the Coinage Act of 1792, when Philadelphia was the nation’s capital. It was the first public building constructed under the direction of the recently formed United States government. The machinery was powered by a horse walking circles in the basement.

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