A-A-53468 Furnace, Dental Laboratory, ElectricThis commercial item description covers an electrically operated, heating plate type, burn-out and heat treating furnace, with pyrometer, automatic temperature controls and replacement heating plates, as specified below: Type I.-complete Furnace Type II,- Replacement Heating Plates Style 1-Rear Plates Style 2- Side Plates.

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A-A-53468

The digital pyrometer shall indicate the actual furnace temperature. The “set” temperature shall be indicated on the pyrometer and adjusted when the “Press-to-Set” switch is depressed. When the switch is released the pyrometer shall indicate the actual furnace temperature. The furnace shall be equipped with an automatic temperature control, which consists of: an 0-4 hour heat soak timer, with an electronic, digital status indicator showing either “Preset”, “Holding” or “End” soak timer modes; an eight position heat rate control; and a “Heater on” indicator.

Housing. The furnace shall have two sections, an upper section and a lower section (instrumentation). The upper section shall be fabricated from 20 gauge (US) type 304 stainless steel. A removable upper rear panel shall be fabricated from 16 gauge (B&S), type 3003-H14 aluminum alloy. The lower section shall be fabricated from 18 gauge (US) cold rolled steel.

Door and door frame. The door and door frame shall be fabricated from 20 gauge (US), type 304 stainless steel.

Heating element. The heating element wire shall be fabricated from an alloy consisting of 5.5 percent aluminum (nominal), 22 percent chromium (nominal) and the balance of iron. The heating element shall be 18 gauge resistance wire.

Refractories and insulation.

Heating chamber. The insulation of the heating chamber shall be fabricated from alumina-silica, ceramic fiber. The blanket insulation used in addition to the ceramic fiber in the heating chamber shall be fabricated from an alumina-silica fiber blanket.

Refractory parts. The heating element supports, and the terminal block which in mounted on the rear insulating panel, shall be fabricated from a castable ceramic material.

Door insulation. The door insulation shall be fabricated from alumina-silica, ceramic fiber.

Insulation between housings. The upper and lower housings of the furnace shall be insulated by an air space of 5/8 inch. This distance shall be maintained by two metal spacer bars between the two sections.