through valve (E) to be indicated on PRES- SURE/SUCTION manometer (4) or Hg manometer (5), whichever you have selected. Any leakage would be registered on rotameters (7) or (8). 5. The VENT PRESSURE valve (H) controls a vent flow of low pressure through the suit simulator tank to the item under test at sea level. When valve (H) is opened, nitrogen (N₂) flows through the vent flow Vol-O-Flo element, and is indicated on VENT FLOW manometer (3). The flow then passes to the suit simulator tank, through FLOW SELECTOR valve (M), OUT- PUT connection (23) and piezometer (26) to the item under test. Valve (H) is primarily used for testing relief valves. 6. The VENT AMBIENT valve (I) serves the same purpose as VENT PRESSURE valve (H), except that valve (H) is used at sea level with supply pressure, while valve (I) is used at altitude and uses ambient air as the pressure source to conserve N₂. Therefore, valve (I) can be considered an economizer valve, used only “at altitude.” Nonmeasunng Control Valves The nonmeasuring valves (fig. 11-1) are opened only as much as necessary. Flow through these valves cannot be measured or gauged. The nonmeasuring valves are as follows: 1. The FLUTTER DAMPENER valve (J) allows an opening from the suit simulator tank to the line connecting FLOW SELECTOR valve (M) and OUTPUT valve (C). It acts as a dampener to prevent fluttering of specific regulator diaphragms during testing, and allows a flow to be drawn from a test item through the suit simulator tank when FLOW SELECTOR valve (M) is in the CONTROLLER position. 2. The CHAMBER BLEED valve (K) is used to bring the chamber to sea level from a simulated altitude. 3. The SYSTEM BLEED valve (S) is used to bleed N₂ pressure from systems of the test stand through SYSTEM BLEED port (16). On later configurations of Model 1172AS100, SYSTEM BLEED port (16) has been deleted. N₂ pressure is bled directly from a port incorporated in the SYSTEM BLEED valve (S). SHUTOFF VALVES There is only one shutoff valve on the 1172AS100 test stand (fig. 1 l-l). It is the SUIT SIMULATOR REFERENCE SHUTOFF valve (R). It is used to prevent damage to other com- ponents. The SUIT SIMULATOR REFERENCE SHUTOFF valve shuts off the suit simulator tank from REFERENCE PRESSURE SELECTOR valve (0) and HELMET REFERENCE TAP (24). When you use a shutoff valve, you should fully open the valve, and then turn it back one-fourth turn. CAUTION IF SUIT SIMULATOR VALVE (R) IS LEFT OPEN WITH REFERENCE PRES- SURE SELECTOR VALVE (0) IN THE SUIT SIMULATOR TANK POSITION, DAMAGE COULD OCCUR TO LOW RANGE ALTM (13) IF EXCESSIVE PRESSURE IS APPLIED TO IT WITH VENT PRESSURE VALVE (H). REGULATORS There are two regulators on the 1172AS100 test stand (fig. 11-1). They control the supply pressure to the specific system being used. The regulators are as follows: 1. The HIGH PRESSURE REGULATOR (Q), which is pneumatically operated. It supplies regulated high pressures from 250 pounds per square inch, gauge (psig) to the maximum capacity of the supply cylinder being used. Regulator (Q) has three positions—LOAD, NEUTRAL, and VENT. It is spring loaded in the NEUTRAL posi- tion. Pressure being loaded is indicated on REGULATED HIGH PRESSURE gauge (10). 2. The LOW PRESSURE REGULATOR (N), which is mechanically operated, supplies regulated low pressure to the item under test, the in-system rotameters, and the suit simulator tank. Regulator (N) has a range of 0 to 180 psig. The pressure being loaded is displayed on REGULATED LOW PRESSURE gauge (1 1), and is also displayed on N₂ INPUT gauge (27) when the INLET PRESSURE ON/OFF valve (L) is in the ON position. GAUGES AND INDICATORS Gauges and indicators incorporated in the test stand (fig. 11-1 ) indicate pressures or flows. Some indicate in pounds per square inch, gauge (psig), some in feet, inches of mercury (inches Hg), 11-7