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![]() TM 9-6685-202-14
for reading. Tighten set screw.
(g) Check
reading
and
reset
if
necessary.
(e) Set micrometer to zero reading.
(h) The barometer is now ready for
(f) Loosen shaft set screw and move
operation.
shaft until slight "dimple" can be seen on the mercury
surface. Tighten the set screw.
Section II. OPERATION UNDER USUAL CONDITIONS
from overload. It is recommended
3-6. Controls
that a suitable motor starting switch
with motor overload protection he
a. The barometer contains no controls that must
used for all permanent installations.
be set prior to operation.
The motor is supplied with a
connecting cord and plug for
b. This section describes the procedure for normal
operation on 115 volts.
For
operation of the barometer. It is assumed that the
operation on 230 volts rewire as
instrument is free from maintenance problems as
shown on inside of the cover of the
ascertained in the inspection procedures in paragraph 3-
motor connection box.
vacuum pump and constant pressure regulator, which
(2) The oil is drained from the pump for
although not part of the barometer, are essential to its
shipment. A gallon of Cenco No. 93050 vacuum pump
operation.
oil is supplied with each pump. Approximately three
quarts are needed in the pump. To fill the pump,
3-7. Operation of Vacuum Pump 4310-2033057 or
remove the top cover and fill with the oil supplied until it
4931-929-8403
is slightly above the oil level as indicated in the window
on one side of the pump. In operation, the oil should be
a. The vacuum pump is a motor-driven, rotary-
even with, or slightly above, the oil level as indicated in
type, oil-sealed pump operating on the principle of the
the window.
eccentric rotor with spring operated moving vanes. Air
at atmospheric pressure is forced into a smaller volume
NOTE
by the action of an eccentric rotor with moving vanes
always in contact, and is expelled from the exhaust port.
The 4931-929-8403 pump is shipped
The pump is a two-stage, series connected type. The
with on quart of Cenco No. 9050
two stages, intake and exhaust, have equal volumetric
vacuum pump oil and is filled
displacement. A single spring actuates each valve. The
through the exhaust port.
entire pump mechanism is immersed in a bath of oil
which insures a tight vacuum seal of the stages, acts as
CAUTION
a coolant, and lubricates the moving parts. The pump
and motor are mounted on a steel base.
Measure the oil carefully.
If
insufficient oil is used, a good seal
b.
To operate the vacuum pump, proceed
around the vane my not be
as follows: (1) Connect the motor to a power source of
maintained. If too much oil is used,
the voltage, frequency and phase indicated on the
oil my back up through the pump
nameplate of the motor, normally 115 volts, 60 cycles,
trap into the vacuum line.
single phase.
CAUTION
(3) When the oil has become contaminated,
as can be seen through the inspection window, drain the
pump, flush with a small amount of vacuum pump oil
The power line would be heavy
and refill with Cenco vacuum pump oil No. 93050,
enough to carry the current required
Federal Stock Number 9150-273-8663. Most of the oil
without an undue drop in voltage.
may be drained through the drain cock.
Fuses
provide
short
circuit
protection only for the power supply
line and do not protect the motor
3-6
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