CHECK VALVE CONNECTIONS
There are four connections located within
the altitude chamber that have check valves
incorporated, and require insertion of a bayonet-
type fitting to open the connection and route the
flow (fig. 11-1). These connections are as follows:
1. The LOW PRESSURE connection (19)
provides for a controlled flow of low-pressure
nitrogen through LEAKAGE CONTROL valve
(E) to the item under test.
2. The 20 to 200 CCM LEAKAGE connec-
tion (20) connects the test item to OVERBOARD
LEAKAGE rotameter (6), and is used when
testing components for leakage or bleed.
3. The REFERENCE TAP connection (21) is
a reference tap to differential pressure indicating
manometers (PRESSURE/SUCTION manometer
(4) and Hg manometer (5)). It also has a reference
line that connects piezometer (26) into
REFERENCE TAP connection (21) downstream
from the check valve.
4. The HELMET REFERENCE TAP con-
nection (24) is a reference tap connected to both
suit simulator tank through SUIT SIMULATOR
REFERENCE SHUTOFF valve (R) or LOW
RANGE ALTM (13) through REFERENCE
PRESSURE SELECTOR valve (O).
NOTE: The CHAMBER REFERENCE
port (N/N), also located within the
chamber, references chamber pressure to
ALT CONTROLLER (B), PRESSURE/
SUCTION manometer (4), Hg manometer
(5), LOW RANGE ALTM (13), and
HIGH RANGE ALTM (12).
Line traps, float check valves, and relief valves
are not shown in figure 11-1.
Line traps are incorporated in PRESSURE/
SUCTION manometer (4) and Hg manometer (5)
to trap liquids in case manometers are over-
loaded.
The float check valves incorporated in the
OUTPUT FLOW manometer (l), the INPUT
FLOW manometer (2), the VENT FLOW
manometer (3) and the PRESSURE/SUCTION
manometer (4) help to prevent a loss of liquid in
case the manometers are overloaded.
The relief valves are incorporated in the
REGULATED LOW PRESSURE gauge (11) and
the suit simulator tank. The relief valve on
the REGULATED LOW PRESSURE gauge
(11) is preset at 200 to 230 psig and protects
the gauge and rotameter system in case of gauge
guard failure. The PRIMARY relief valve is
preset at 15 psig and the SECONDARY relief
valve is preset at 25 psig. These relief valves
prevent overpressurization of the suit simulator
tank.
VACUUM PUMP
The VACUUM PUMP (VP) operates from a
2 horsepower electric motor (fig. 11-3). The pump
rotation is clockwise, when viewed from the rear
of the test stand. The pump has the capability of
evacuating the chamber at a rate of 22.5 cubic feet
per minute (cfm) at 81 mm Hg (51,600 feet)
simulated altitude. It is used to evacuate the
chamber or draw flow of air, nitrogen, or air and
nitrogen from an item under test. The VACWM
11-9
239.478
Figure 11-3.—Vacuum pump.
