2-12. Muffle Furnace.
(1) Place the toggle switch in the ON position.
The pilot light is illuminated while heat is on.
designed to comply with the requirements specified in
(2) Set the percentage timer. The timer operates so
ASTM D482, D874, and D2276 (TM 10-1166), is located
that heat is on for a set percentage of 1 minute and off
on the left-hand work counter (fig. 1-2). The furnace is
the remaining part. For example, with the timer set at
used for heat treating, precipitate drying, ashing, igniting,
20, the heat is on 20 percent of 1 minute and off 80
and fusing. It has a continuous operating temperature
percent; a setting at 60 controls temperature at
range from 150 degrees F to 1800 degrees F (66
approximately 1800 degrees F (982 degrees C).
degrees C to 982 degrees C). Intermittent heating as
high as 2000 degrees F (1093 degrees C) will not
(3) For quick heat-up, set the timer at 100 which
damage the muffle winding or refractories. The furnace
provides continuous heating, but make sure to turn back
consists essentially of a muffle chamber with drop door
the timer when pyrometer shows temperature reading at
and steel tray, and a base which houses a temperature
1800 degrees F (982 degrees C) to prevent burning out
gage (pyrometer) showing both Fahrenheit and
of heaters, refractories, etc., caused by excessive
Centrigrade scales, percentage timer, pilot light, and ON-
OFF toggle switch.
Figure 2-5. Muffle Furnace.