PUMP vent (54) must be opened one to two turns when you operate the pump (fig. 11-1). WARNING ALWAYS ENSURE THAT THE PUMP MOTOR HAS A FOUR-PRONG ELEC- TRICAL CONNECTION PLUG. ON MODEL 1172AS100 ENSURE THAT THE GROUNDING LUG IS IN PLACE AND SECURELY CONNECTED. A SIDE VIEW OF THE VACUUM PUMP IS SHOWN IN FIGURE 11-3. SAFETY PRECAUTIONS Before you attempt to operate the test stand, review the following safety precautions. These safety precautions must be observed before, during, and after test stand operation. 1. Ensure that the test stand is properly secured prior to opening the supply cylinder valve. Position the HIGH PRESSURE REGULATOR to LOAD, then to VENT, and ensure that the LOW PRESSURE REGULATOR is backed out and the other valves are turned fully to the right. 2. Keep the chamber door closed whenever possible. 3. Keep the test stand doors closed at all times. 4. Keep the test stand work tray closed when it is not in use. 5. Check the pump lubricant prior to turn- ing the pump on (run for 2 minutes and check lubricant for proper level). 6. Keep your hands and head clear of belts and pulleys while checking the lubricant level. 7. Ensure the test stand is properly grounded by using the grounding lug. 8. Never use regulated high pressure and regulated low pressure together. 9. When the oxygen monitor alarm sounds, leave the room. 10. Do not panic when the test stand malfunctions. 11. When you use nitrogen, ensure that the room is well ventilated. 12. Use proper tools for the job you are performing. 13. Do not inhale lubricant, oxygen cleaning compound, or mercury fumes. 14. Wash pump lubricant or mercury from hands immediately. 15. Secure the test stand completely after use. 16. Never leave the test stand unattended while the pump is running. 17. When transporting the compressed nitro- gen cylinder, you should ensure the protective cap is on. MAINTENANCE Maintenance on the oxygen components test stand is discussed in the following paragraphs. MANOMETER PREPARATION Maintenance on the 1172AS100 begins as soon as the test stand is uncrated. You should fill the OUTPUT, INPUT, and VENT FLOW ma- nometers with a liquid that has a known specific gravity of 1.0. The liquid used for the 1172AS100 is a mixture of one part concentrated green manometer fluid (merian D-2930) mixed with 10 parts of water. To fill the manometers, your first step is to adjust the scale so that the zero is located half way between the full-up and the full-down position. Remove the fill plugs from the manometer reservoirs and fill the reservoir until the fluid reaches the zero mark on the scale. After you have filled the reservoir to zero, replace the fill plugs. To fill the pressure suction manometer with fluid, use red manometer fluid with a specific gravity of 1.9. The procedure is the same. Adjust the scale so the zero mark is half way between the full-up and full-down positions. You have one more type manometer to fill. The Hg manometer uses triple-distilled mercury. To fill this manometer, follow the same procedure that you used for the other manometers. Do not spill the mercury. If you do, notify your supervisor, and follow the special precautions for cleaning mercury spills. PRESSURE/LEAKAGE TESTS To ensure maximum operating efficiency, pressure/leakage tests must be performed periodically. NOTE: Use systems schematic drawings as an aid in determining any malfunctions that may exist.    You can find these schematics in NAVAIR 13-1-6.4. 11-10