TM 5-6640-212-14
(6)
When oven has reached the desired
(4) The pyrometer indicates the temperature inside
temperature, turn the temperature control knob
the furnace and can be calibrated for difference in room
counterclockwise until the heat shuts off, as indicated by
temperature by means of the screw on the panel.
the pilot lamp being extinguished.
(5) For test procedures that use the muffle furnace,
(7) Before final temperature adjustment is made,
refer to ASTM Method D482, D874, and D2276 (TM 10-
allow about an hour for oven heat to stabilize. If, after
1166).
elapsed time, temperature is not at desired degree, turn
temperature control knob to raise or lower the
temperature as required until desired temperature is
2-13. Oven.
attained.
a. Description. The utility oven (fig. 2-6) is located
NOTE
on the left-hand countertop. The oven is used for
When the temperature control is
baking, drying, conditioning preheating and produces
moved from a higher to a lower
heat ranging from ambient to 200 degrees C. The
setting, the safety pilot light may flow
cabinet type, gravity convection oven is equipped with a
hydraulic, snap-action thermostat, two adjustable latticed
faintly for a short time.
This is
metal shelves (fig. 2-6), hinged door with safety latch,
inconsequential
and
light
will
adjustable ventilator, pilot light, ON-OFF toggle switch
disappear as soon as the new lower
and a thermometer ranging from 0 degree to 2000
temperature is stabilized.
degrees C.
2-14. Kinematic Viscosity Baths.
b. Operation.
a. Description. Two kinematic viscosity baths(fig. 2-
(1) Insert the thermometer through the hole in the
7) are mounted on the left-hand counter of the laboratory
center of the exhaust vent shutter in top of the oven, and
compartment. The kinematic viscosity bath is designed
open the vent shutter. Make sure that the thermometer
to comply with the requirements specified in ASTM D445
bulb extends as far into the heating chamber as possible
(TM 10-1166). It is used to determine the kinematic
to insure correct temperature reading.
viscosity of petroleum products.
Each apparatus
(2) In loading the oven, whenever possible, use only
includes a constant temperature bath consisting of a
one shelf and leave ample space between objects for
plastic cylinder, stirrer and motor, and a mercury
proper air circulation and maximum heat transfer. Never
thermoregulator.
The
thermoregulator
and
place materials on oven floor or below lowest shelf
thermoregulator guard are stored in drawer El (fig. B-
position. Shelves should not be overloaded and should
11). Each bath accommodates three capillary type
never be loaded from wall to wall.
viscometer tubes. The viscometer tubes are stored in
(3) Always leave the shutter in the exhaust vent at
drawer C1 (fig. B-9). The paper charts are stored in
least one-fourth open. As oven operates by gravity
drawer A5 (fig.
B-7) and P2 (fig.
B-21).
The
convection, air circulation is vertical. Air enters through
temperature range of the bath is 68 degrees F to 250
opening in oven bottom, passes over the heater, and
degrees F (20 degrees C to 121 degrees C). The heater
then through perforations of heater plate into the cabinet
rotary switch has five positions: OFF, LOW (125 watts),
where it passes through the exhaust vent. By opening
MEDIUM LOW (200 watts), MEDIUM (300 watts), and
the shutter, air movement within the oven is increased,
HIGH (500 watts).
and more fresh air is introduced.
(4) Place the toggle switch in the ON position.
b. Operation.
(5) As reference points on the temperature control
knob do not correspond with temperature set-tings,
(1) Remove one of the circular bakelite cover and
temperature readings must be taken from the
clip assemblies and fill the bath to approximately 1 1/2
thermometer.
To raise the temperature, turn the
inches (38.1 mm) from the top with a suitable white
temperature control knob clockwise until the pilot light
technical oil. Determinations above 100 degrees F (37.8
indicates that the heaters are on.
To lower the
degrees C) requires the use of oil (48619) 74972.
temperature, turn the knob
Determinations below 100 degrees F (37.8 degrees C),
require the use of oil (48619) 74974. Do not use water in
the bath, as this will short out the heaters.
counterclockwise. When turning the temperature control
knob clockwise, back off slightly to take up lose motion in
thermostat mechanism.
2-12
