TM 55-1930-209-14&P-19 Table 7-2.  Preventive Maintenance Checks and Services for Compressed Air System (Continued) B - Before D - Daily Q -  Quarterly D - During W - Weekly S -  Semiannually A - After M - Monthly A -  Annually INTERVAL ITEM PROCEDURES EQUIPMENT ITEM TO BE CHECK FOR AND HAVE IS NOT READY/ NO. INSPECTED REPAIRED OR ADJUSTED AVAILABLE IF B   D   A   D  W  M   Q   S   A AS NECESSARY 8) Replace bowl O-ring if damaged or worn. 9) Carefully install bowl O-ring and metal bowl.  Hold in place by hand and screw bowl ring nut onto threads on filter head.  Make sure O-ring is properly seated and then tighten hand-tight. 10) Start air compressor system. 11) Remove red tag from power panel 1 circuit breaker 3P5. Air Pressure Regulator NOTE Semiannually   or   after   1000   hours   of equipment operation (whichever occurs first). Air pressure regulators 1 and 2.  Upon detec- tion of leaks, pressure fluctuation, pressure creep, or for semiannual maintenance ser- vices, perform these procedures: 1) Shut down air compressor system. 2) Redtag power panel 1 circuit breaker 3P5 indicating, 'WARNING - DO NOT ACTIVATE.  REPAIRS BEING MADE." 3) On air pressure regulator, unscrew bottom plug (or pressure gauge if installed in this manner) and remove bottom plug O-ring, bottom spring and disc assembly.  Inspect valve seat for damage or wear. 4)  Inspect valve seat in head casting for foreign material or damage.  Clean with soapy water, rinse, and dry with lint-free cloth. 7-28