SERVICE MANUAL 1 RETAINER, Spring 17 O-RING 2 RING, Retaining 18 RING, Retaining 3 RING, Retaining 19 O-RING 4 BODY, Valve (Primary) 20 SPRING 5 O-RING 21 BODY, Valve (Secondary) 6 RING, Reaction 22 SPRING 7 SPRING 23 PISTON, Secondary 8 RETAINER, Seal 24 O-RING 9 BODY, Exhaust Valve 25 TAG, Name 10 O-RING 26 RING, Retaining 11 O-RING 27 O-RING 12 BODY, Exhaust Valve 28 SCREW 13 DIAPHRAGM 29 VALVE AND SEAL 14 SCREW 30 SHIM 15 RETAINER.  Washer 31 PISTON, Primary 16 VALVE AND SEAL 32 COMPENSATOR, Spring assembly (8 and 16) to move away from the inlet seat of valve     body     (21)     allowing     the     secondary     reservoir pressure    "J"    to    enter    cavity    "H"    and    flow    out    the secondary delivery port. Release of Primary Section When   force   is   removed   from   the   foot   valve   actuator (treadle   or   pedal),   force   is   removed   from   the   spring retainer  (1),  compensating  spring  (32)  and  the  primary piston (31).  The primary piston moves upward due to air pressure  in  cavity  "A"  and  a  force  of  return  spring  (7). This  allows  the  rubber  face  seal  (29)  to   seat   against valve body (4) and causes the primary piston exhaust seat "B" to  move  away  from  the  rubber  face  of  seal  (29).    This allows  primary  delivery  air  pressure  to  exhaust  through cavity "C" and "K" out to atmosphere around the exhaust port diaphragm(13). Release of Secondary Section When  air  pressure  is  exhausted  from  primary  delivery section,  air  pressure  is  also  exhausted  from  the  bleed hole "E" and cavity "F." The secondary piston (23) moves upward  due  to  air  pressure  in  cavity  "H"  and  a  force  of the return CTS-4079 - CHAPTER - Page 12