SERVICE MANUAL 2. Remove   diaphragm   spring   cap   or   diaphragm protector, spring and shim from upper body.  Be sure  to  retain  shim  which  is  used  to  adjust  the pressure regulation of the valve. CLEAN AND INSPECTION 1. Clean  all  parts  in  good  cleaning  solvent.    Make sure    vent    hole    in    upper    valve    body    is    not obstructed. 2. Inspect  diaphragm,  especially  at  lower  contact area. 3. Replace  any  parts  that  show  wear  or  spring  if distorted. 4. Inspect  the  diaphragm  seat  for  pitting  or  nicks. The  seat  should  be  smooth,  if  not,  it  may  be dressed   with   emery   cloth.      Replace   complete valve assembly if excessive pitting is found. REASSEMBLY (Refer to Fig. 5) 1. Position the shim if used in the upper body.  The same number of shims should be used to obtain proper pressure adjustment. 2. Position  spring,  spring   cap   and   diaphragm   on upper body. 3. Place  lower  body  over  the  assembly  and  force the two body halves together. 4. Turn assembly over and install screws. 5. Test repaired valve assembly. TEST REPAIRED VALVE Prior  to  installing  the  repaired  valve  assembly  the  valve should be tested for leakage and proper adjustment. Assemble air gauge and shut-off valve at inlet and outlet of  pressure  protection  valve  then  connect  to  shop  air source.        Open    shut-off    valve    at    outlet    of    pressure protection   valve   and   slowly   open   shut-off   valve   at   air source   until   air   pressure   reaches   379   kPa   (55   psi). Check   for   air   leakage    with    soap    solution    at    outlet. Leakage  must  not  exceed  90  cc  per  minute  (I  in.    soap bubble in 6 seconds). Close    the    shut-off    valve    at    outlet    and    increase    air pressure at inlet side of pressure protection valve.  No air pressure   at   outlet   air   gauge   should   be   available   until pressure  re-reaches  448-517  kPa  (65-75  psi)  at  inlet. Then both gauges should equalize. If  pressure  protection  valve  opens  prior  to  448  kPa  (65 psi) add shim  to valve and if valve remains closed after 517 kPa (75 psi) is obtained remove shim. After valve has been tested and meets requirements, it is ready to be installed on vehicle. PRESSURE REDUCING (LIMITING) VALVE DESCRIPTION The pressure reducing (limiting) valve is used to reduce air’ pressure and maintain it at a constant specified pre- set pressure below that of the supply pressure (Fig. 6 ). The  pressure  reducing  valve  has  a  delivery  port  on  the side  and  a  supply  port  on  the  bottom.    Two  mounting holes  are  cast  into  the  body.    A  lockwire  and  seal  are optional for a tamper proof setting. Fig. 6 Pressure Limiting Valve 1 Adjusting Cap 4 Mounting Holes 2 Lock Nut 5 Supply Port 3 Delivery Port OPERATION (Refer to Fig. 7) The   pressure   setting   of   the   pressure   limiting   valve   is determined  by  the  setting  of  the  adjusting  cap,  which exerts   a   force   on   the   spring   on   top   of   the   piston. Compressed  air  enters  the  supply  port  and  passes  out the delivery port.  When the air pressure on the bottom of the  piston  overcomes  the  force  of  the  spring  on  top  of the  piston,  the  piston  moves  upward  and  the  inlet  valve spring  forces  the  inlet  valve  on  its  seat,  closing  off  the supply of air.  As the pressure in the delivery line drops, the force of the spring above the piston becomes greater than   the   air   pressure   below   the   piston,   allowing   the piston  to  move  downward,  moving  the  inlet  valve  off  its seat and allowing air to pass out the delivery port. CTS-4079 - CHAPTER III PRINTED IN UNITED STATES OF AMERICA Page 6