Inward Leakage Test

By applying 9.0 inches (H2O) of suction to the regulator outlet, you are testing the regulator to be leaktight. If a leak is present, it could effect other tests covered in the chapter. It could also prevent the aircrewman from receiving 100-percent oxygen by allowing ambient air to enter the regulator.

To perform the inward leakage test, proceed as follows:

1. Ensure that all test stand valves are closed, then open N2 supply cylinder valve.

2. Place the regulator supply control valve lever in the OFF position, and the diluter control lever in the 100-percent OXYGEN position.

3. Ensure that the regulator emergency pressure control lever is in the NORMAL position.

4. Mount the adapter supplied with the test stand (NAVAIR Drawing No. 1172AS136), and connect the regulator outlet to the N2 INPUT connection in the altitude chamber.

5. Connect a line from the LOW PRESS connection to REFERENCE TAP in the altitude chamber. Plug the rubber hose attached to the piezometer by using the piezometer plug supplied with the test stand. Ensure that the LOW PRESSURE REGULATOR is not loaded. This will prevent N2 supply cylinder pressure from passing onto the INLET PRESSURE ON/OFF valve which could damage the test item or injure the test stand operator.

6. Turn the INLET PRESSURE ON/OFF valve to the ON position. The vacuum vent must be opened one to two turns when you operate the vacuum pump. Turn the vacuum pump on.

7. Turn the PRESSURE SELECTOR valve LEAKAGE CONTROL valve. to the H2O position, and fully open the

8. Ensure that the LEAKAGE SELECTOR valve is in the HIGH RANGE position.

9. The leakage rotameter is calibrated with an applied pressure of 70 psig. The inward leakage test requires that a suction of 9.0 in H2O be applied to the regulator outlet and the rotameter. This pressure difference (9.0 in H2O vice 70 psig) creates a wide variance between actual leakage and _{indicated leakage.} The maximum allowable leakage for the inward leakage test is 200 cubic centimeters per minute, and is displayed as 740 ccm on the high range leakage rotameter.

NOTE: Because of labeling on gauges, the abbreviation ccm is used in this text. Since the cubic centimeter has been replaced by the milliliter, this abbreviation should be ml/min instead of ccm. The proper abbreviation may appear on later equipment and newer technical manuals.

Slowly open the OUTPUT valve until 9 inches of H2O suction is indicated on the PRESSURE/SUCTION manometer. Any leakage will be displayed on the HIGH RANGE LEAKAGE rotameter. The maximum allowable indicated leakage reading is 740 ccm (actual 200 ccm). Record the indicated leakage on the Performance Test Sheet.

10. Close the OUTPUT valve and the LEAKAGE CONTROL valve. Turn the vacuum pump OFF. Turn the INLET PRESSURE ON/OFF valve to the OFF position.

Table 12-5A.-Troubleshooting (Inward Leakage Test)

11. Disconnect the line from the LOW PRESSURE connection and REF. TAP in the altitude chamber. Disconnect the regulator outlet from N2 INPUT connection, and remove the plug from the piezometer.

12. If excessive leakage is indicated, locate the probable cause by using troubleshooting chart, table 12-5A.

Outlet Leakage Test

To perform an outlet leakage test, proceed as follows:

1. Place the regulator supply valve control lever in the ON position.

2. Ensure that the diluter control lever is in the 100-percent OXYGEN position.

3. Place the emergency pressure control lever in the NORMAL position.

4. Mount the regulator on a horizontal plane in the test chamber. Connect the regulator inlet to the N2 INPUT connection (18) inside the altitude chamber.

5. By using the LOW PRESSURE REG-ULATOR, apply 150 psig to the regulator inlet.

6. Slowly turn the INLET PRESSURE ON/OFF valve to ON.

7. Activate the emergency pressure control lever to allow a flow through the regulator, then return the lever to its NORMAL position.

8. Draw a film of leak detection compound (MIL-L-25567) across the regulator outlet. The film should not advance more than 1/2 inch in 10 seconds. If the film advance is more than allowable, repeat the test three or four times. (Distention could be caused by difference in temperature between inside and outside of regulator.)

9. If the film advance continues to be more than allowed, locate the probable cause by using the troubleshooting chart, table 12-5B.

10. Relieve pressure on the regulator by backing out on the LOW PRESSURE REGULATOR.

OXYGEN SUPPLY VALVE LEAKAGE TEST.- If the supply pressure could not be shut off, until a demand was placed on it, a pressure buildup could be created. It could damage the regulator hose or mask and possibly injure the crewmen. To perform the oxygen supply valve leakage test with the regulator still mounted in the chamber, proceed as follows:

1. Place the regulator oxygen supply valve lever in the OFF position.

Table 12-5B.-Troubleshooting (Outlet Leakage Test)

2. Place the emergency pressure control lever in the EMERGENCY position.

3. Using HIGH PRESSURE REGULATOR, apply pressure specified in table 12-6 to the regulator inlet. Slowly turn the INLET PRESSURE ON/OFF valve to ON.

4. Draw a film of leak detection compound (MIL-L-25567) across the regulator outlet fitting. As in the last test, see if there is any distention of the film.

5. There is no allowable leakage. If leakage is noted, locate probable cause using troubleshooting chart, table 12-7.

6. Place the emergency control lever in the NORMAL position.

OVERALL LEAKAGE TEST.- Test, by trapping pressure in the regulator, for any leakage anywhere on or in the regulator. Perform the overall leakage test first with diluter lever in its 100-percent OXYGEN position, and then repeat it with the lever in the NORMAL OXYGEN position.

1. Place regulator oxygen supply valve lever in the ON position, and emergency pressure control lever in the NORMAL position.

2. By using test stand HIGH PRESSURE REGULATOR, apply pressure specified in table 12-8 to regulator inlet.

3. Turn INLET PRESSURE ON/OFF valve to OFF. Leave the regulator oxygen supply valve lever in the ON position.

4. Leakage will be indicated on the regulator pressure gauge. Allowable leakage should not exceed 60 psig over a 2-minute period. Repeat the test with the diluter lever turned to NORMAL OXYGEN.

Table 12-6.-Inlet Pressure (Oxygen Supply Valve Leakage Test)

5. If allowable leakage is exceeded, locate the probable cause by using the troubleshooting chart, table 12-9.

6. Turn the HIGH PRESSURE REGULA-TOR to VENT.

7. Bleed the regulator by placing the emergency pressure control lever in the EMERGENCY position. Return the lever to NORMAL.

8. Bleed the test stand using the SYSTEM BLEED valve.

REGUI.ATOR PRESSURE GAUGE SCALE AND ERROR TEST.- This test ensures that the pressure gauge is operating properly and within tolerance. To perform the regulator pressure gauge scale and error test, proceed as follows:

1. Turn the INLET PRESSURE ON/OFF valve to ON. The LOW PRESSURE REGULA-TOR can only be used when applying pressures below the gauge guard setting (165 to 175 psig) to an item under test. For pressures above the gauge guard setting, the HIGH PRESSURE REGULATOR must be used.

2. Using LOW PRESSURE REGULATOR (N), slowly increase the pressure to each test pressure in 100 psig increments and below, as specified in table 12-6. Record the regulator pressure gauge readings twice, once before and once after tapping regulator pressure gauge.

3. Check the tolerance by comparing the regulator pressure gauge reading with the test stand INPUT PRESSURE gauge.

4. Back out on the LOW PRESSURE REGULATOR.

5. Continue the test for 500 psig pressure by using the HIGH PRESSURE REGULATOR.

6. Turn the HIGH PRESSURE REGULA-TOR to VENT.

7. Bleed the test standby using the SYSTEM BLEED valve. Bleed the regulator using the emergency pressure control lever.