TM 10-6640-238-13 4-172 4-71.    OXYGEN AND NITROGEN GAS SUPPLY LINES. This task consists of: a. Remove b. Install INITIAL SET-UP Tools Required General Mechanics Tool Kit, (Appendix B, Section III, Item 1) Materials/Parts Required Teflon Tape, (Appendix E, Section II, Item 157) General Safety Instructions WARNING Pressure systems safety precautions apply to all ranges of pressure.  Care must be taken  during  testing  to  ensure  that  all  test  connections  are  properly  and  tightly made prior to applying pressure to the test setup.  Ensure gas cylinder valves are tightly closed prior to removing/replacing gas cylinders. REMOVE 1. Remove Oxygen and Nitrogen Supply Hoses.  See Figure 4-67. a. Open gas cylinder cabinet door. b. Close gas cylinder discharge valves (1). c. Disconnect oxygen and nitrogen supply hoses (2) from gas cylinder discharge valves (1). d. Disconnect oxygen and nitrogen supply hoses (2) from pipe nipples (3). 2. Remove Oxygen and Nitrogen Supply Piping. a. Remove sections of system piping (4) by locating nearest pipe union (5), pipe elbow (6) or adapter (7). b. Disconnect union (5) and/or pipe elbow(s) (6). c. Remove screws (8), washers (9), and clamps (10) as applicable and remove system piping (4). 3. Remove Oxygen and Nitrogen Supply Valves. a. Disconnect valve (11) from pipe nipple (12). INSTALL 1. Install Oxygen and Nitrogen Supply Valves.  See Figure 4-67. a. Replace teflon tape on male fittings.  Be sure to wrap teflon tape in same direction of pipe thread. b. Install valve (11) by screwing valves onto pipe nipple (12). 2. Install Oxygen and Nitrogen Supply Piping. a. Apply teflon tape on male fittings.  Be sure to wrap teflon tape in same direction of pipe thread. b. Install system piping (4) and secure with screws (8), washers (9), and clamps (10) as applicable. c. Connect system piping (4) to union (5) and/or pipe elbow(s) (6).