11 Fittings for industrial furnaces and machines, namely, low pressure carburizing systems comprising carburizing furnaces; vacuum carbonitriding systems comprising carbonitriding furnaces; high pressure gas quench systems and vacuum oil quenching systems comprising quenching apparatus for heat treatment; industrial installations, namely, industrial installations for crystal growth in the nature of furnaces; machines for production of protective gases as control and safety apparatus, namely, pressurized inert gas circulation system for cooling treated materials; furnaces, gas quenching installations, cleaners, purifiers and adsorption apparatuses, namely, cooling units for industrial purposes, gas recycling system comprised primarily of pressure swing adsorption equipment for the recovery, purification and return of gases in industrial applications; industrial furnaces, namely, electrically, gas, oil, or induction heated industrial furnaces; industrial treatment installations, namely, furnaces; furnaces for the treatment of metal or alloy parts; industrial ovens and furnaces for vacuum heat treatment, not for food or beverages; vacuum furnaces; prefabricated furnace elements, namely, heating elements; stokers for use with industrial furnaces; burners, namely, oil and gas burners for industrial use; remelting installations, especially for steel and superalloys, namely, furnaces; industrial installations for melting or hardening, carbonization, gas quenching, sintering in furnaces and/or annealing, especially of metals, metalloids or metal alloys, namely, furnaces and related quenching apparatus for heat treatment; furnaces for metallurgy; vacuum furnaces for use in recycling processes; drying apparatus for metal treatment; tempering installations, namely, heating and cooling installations to change the mechanical and corrosion properties of materials; installations, apparatuses and machines for heating, namely, furnaces; chamber furnaces incorporating quenching tanks; vacuum chamber furnaces; cooling apparatuses, namely, cooling units and freeze drying machines for industrial purposes; cold storage rooms, refrigeration equipment, namely, rapid food chilling units; cooling elements; heating elements; heating apparatus for furnaces; heat exchangers not being parts of machines; industrial installations for tempering, hardening, carbonitriding, case hardening, brazing, sintering by chemical processes, namely, vacuum heat treatment systems comprising industrial furnaces; industrial installations for metal, metalloid and metal alloy processing, namely, metallurgy machines and vacuum heat treatment systems comprising industrial furnaces