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The modernized StrikoMelter at Česká Zbrojovka, a Czech manufacturer of pistols, rifles, and automatic firearms.

Aluminum Melting Back on Target

May 14, 2017
Shaft melting furnace modernization pays off quickly for firearms manufacturer Unavoidable relining Retrofitted shaft-filling level laser New scrap-charging unit

A company called Česká Zbrojovka may be well known to shooting-sports aficionados; the literal translation of the name is Czech Armory, and its CZ brand is found on numerous types of pistols, rifles, and automatic firearms. Still, one of the group’s primary activities is casting aluminum, and recently a comprehensive modernization of its melting system has delivered 40% higher productivity and 20% less energy consumption, returning the capital investment cost in the first year.

The foundry at Strakonice, in the Czech Republic, installed the StrikoWestofen shaft melting furnace (known as the StrikoMelter) in 1998, and though the operators realized the melting performance had declined they preferred modernization to replacement. The furnace designers undertook the project, focusing on the furnace lining as the strategy to increase productivity and energy efficiency.

Depending on the operational demands and the wear, relining is unavoidable working life of a furnace. “Flow guidance” and lining structure are critical factors in achieving energy efficiency of any melting furnace, according to StrikoWestofen. As such, its modernization strategy centered on the geometry of the lining and lining materials. Relining at Česká Zbrojovka was carried out according to the latest technological understanding of these details, which helped to realize significant energy savings while increasing the melting performance.

The Strakonice foundry had also decided to retrofit a shaft-filling level laser during the same period, so that the charging cycles could be optimized – meaning that the furnace shaft maintains an optimal filling level at all times. As such, the StrikoWestofen ETAMax principle of integrated heat recovery is fully applied. Through intelligent utilization of the waste heat in the melting shaft, fuel consumption and metal loss are considerably lower than they would be with comparable preheating technologies.

And, StrikoWestofen installed a new scrap-charging unit. Along with greater operating reliability, the new scrap-charging system contributes to melting efficiency and system productivity.

The primary goal for the upgrade was to reduce the energy consumption to 670 kWh/t. The actual result exceeded that target,  with energy consumption measured at 520 KWh/t after modernization — or, 52 m3 of natural gas per metric ton of molten aluminum. Also, the project also increased melting performance by 40%, one metric ton/hour hour to about 1.4 metric tons/hour.

“We didn’t think it was possible,” commented Petr Havelec, metallurgy director for Česká Zbrojovka. “Also, thanks to the smooth handling, we had next to no downtime and were able to take the furnace back into operation after a short time. Now the modernized furnace can match the performance of a comparable new installation.”

Looking forward, the CZ foundry engaged StrikoWestofen to revamp a second StrikoMelter to the new performance standard.