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Figure 11-1.Controls and indicators for Oxygen System Components Test Stand Model 117AS100
Nonmeasunng Control Valves

Aircrew Survival Equipmentman 2 - Aviation theories and other practices
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(See figure 11-2.) Baffles inside the element create a flow restriction. As air or nitrogen enters the element, a pressure buildup is created at the inlet end; as it flows past the baffles, a pressure drop occurs at the outlet end. The inlet (pressure buildup) tap is connected to the bottom of the in- dicating manometer, and the outlet (pressure drop) tap is connected to the top of the manometer. As the control valve is opened, gas flows from the valve through the Vol-O-Flo, and the pressure drop thus created allows the fluid in the manometer to rise. The operator reads the amount of flow passing through the V0l-O-Flo on the indicating manometer. CONTROL VALVES A control valve regulates, or restricts, a specified flow. Two types of control valves, measuring and nonmeasuring, are used on the test stand. Measuring control valves have measuring devices (gauges or manometers) to visually measure the flow through the valve as it is opened. Nonmeasuring control valves have no indicating devices. There are six measuring and three nonmeasuring control valves on the test stand. Measuring Control Valves The measuring control valves (fig. 1 l-l) are as follows: 1. The INPUT valve (A) allows a measurable flow of air into the altitude chamber. It can only be used during simulated altitude conditions. As the chamber altitude increases, pressure inside the chamber decreases, and the ambient air pressure outside the chamber is greater. When valve (A) is opened, air from outside the chamber flows through valve (A); through the input Vol-O-Flo element, indicating the amount of air flow on the INPUT FLOW manometer (2); and through the INPUT port (22) into the chamber. 2. The VACUUM CONTROL valve (B1) on Model 1172AS100 allows direct evacuation of the altitude chamber to the desired simulated altitude by decreasing pressure in this chamber. 3. The OUTPUT valve (C), when opened, draws a direct flow from the item under test through the piezometer (26), OUTPUT port (23), FLOW SELECTOR valve (M) and the output Vol-O-Flo element to the vacuum pump. As the flow passes through the output Vol-O-Flo, the pressure is displayed on the OUTPUT FLOW manometer (1). 4. The LEAKAGE CONTROL valve (E) controls the flow to the LOW-PRESSURE connection (19), which is located inside the chamber. As the name of the valve implies, it is used to perform various leak tests on oxygen components. When you use the LEAKAGE CONTROL valve (E) to perform leakage tests on components, a line with bayonet fittings must be installed between the LOW-PRESSURE connection (19) and the REFERENCE-TAP connection (21 ). This allows the flow passing Figure 11-2.—VOI-O-FIO element. 11-6 239.477







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