crankshaft  seal  is  bathed  in  lubricating  oil  at  a  pressure equal  to  the  suction  pressure  of  the  refrigerant.  The  first indication of crankshaft seal failure is excessive oil leaking  at  the  shaft. When  the  seal  must  be  replaced  or  when  it  shows signs  of  abnormal  wear  or  damage  to  the  running surfaces, a definite reason can be found for the abnormal conditions.  Make  an  inspection  to  locate  and  correct  the trouble,  or  the  failure  will  recur. Seal   failure   is   very   often   caused   by   faulty lubrication, usually because of the condition of the crankcase oil. A dirty or broken oil seal is generally caused  by  one  or  both  of  the  following  conditions: - Dirt or foreign material is in the system or system piping. Dirt frequently enters the system at the time of installation.  After  a  period  of  operation,  foreign  material will  accumulate  in  the  compressor  crankcase,  tending  to concentrate  in  the  oil  chamber  surrounding  the  shaft seal.  When  the  oil  contains  grit,  it  is  only  a  matter  of  time until   the   highly   finished   running   faces   become damaged,  causing  failure  of  the  shaft  seal. -  Moisture  is  frequently  the  cause  of  an  acid condition  of  the  lubricating  oil.  Oil  in  this  condition  will not provide satisfactory lubrication and will cause failure  of  the  compressor  parts.  Use  a  refrigerant dehydrator  when  the  compressor  is  put  into  operation  if you suspect that moisture may be a problem. Anytime foreign   material   is   found   in   the   lubricating   oil, thoroughly  clean  the  entire  system  (piping,  valves,  and strainers). REMOVING A SHAFT SEAL.—If a shaft seal must  be  removed,  proceed  as  follows: If the seal is broken to the extent that it permits excessive oil leakage, do NOT attempt to pump the refrigerant  out  of  the  compressor.  If  you  do,  air containing moisture will be drawn into the system through  the  damaged  seal.  Moisture  entering  the refrigerant  system  may  cause  expansion  valves  to freeze.  This  can  cause  acid  formation  and  other problems.  If  oil  is  leaking  excessively,  close  the compressor  suction  and  discharge  valves  and  relieve  the pressure  to  the  atmosphere  by  loosening  a  connection on  the  compressor  discharge  gauge  line. Next,  drain  the  oil  from  the  compressor  crankcase. Since  the  oil  contains  refrigerant,  it  will  foam  while being drained. Leave the oil drain valve or plug open while  you  are  working  on  the  seal.  This  ensures  that refrigerant  escaping  from  the  oil  remaining  in  the crankcase  will  not  build  up  pressure  and  blow  out  the seal  while  it  is  being  removed. Remove  the  compressor  flywheel  (or  coupling)  and carefully   remove   the   shaft   seal   assembly.   If   the assembly  cannot  be  readily  removed,  build  up  a  slight pressure  in  the  compressor  crankcase.  To  do  this, slightly  open  the  compressor  suction  valve.  Take  the necessary  precautions  to  support  the  seal  and  to  prevent it  from  being  blown  from  the  compressor  and  damaged. INSTALLING  A  SHAFT  SEAL.—Clean   and replace  the  entire  seal  assembly  according  to  the manufacturer’s     instructions. Wipe  the  shaft  clean  with  a  linen  or  silk  cloth;  do not  use  a  dirty  or  lint-bearing  cloth.  Be  careful  not  to touch the bearing surfaces with your hands as you unwrap  the  seal.  Rinse  the  seal  in  an  approved  solvent and allow it to air-dry. (Do NOT wipe the seal dry!) Dip the  seal  in  clean  refrigerant  oil.  Follow  the  instructions found  in  the  manufacturer’s  technical  manual  to  insert the assembly. Bolt the seal cover in place and tighten the bolts  evenly.  Replace  the  flywheel  and  belts  or  coupling and check and correct the motor and compressor shaft alignment.  To  test  the  unit  for  leaks,  open  the  suction and  discharge  valves  and  use  a  halide  leak  detector. Evacuating  the  Compressor Whenever  repairs  to  a  compressor  allow  any appreciable  amount  of  air  to  enter  the  unit,  the compressor  should  be  evacuated  after  assembly  is completed and before it is ready for operation The proper  procedure  is  as  follows: 1. Disconnect a connection in the compressor discharge  gauge  line  between  the  discharge  line  stop valve  and  the  compressor. 2. Start the compressor and let it run until the greatest  possible  vacuum  is  obtained. 3.  Stop  the  compressor  and  immediately  open  the suction  stop  valve  slightly.  This  will  blow  refrigerant through  the  compressor  valves  and  purge  the  air  above the  discharge  valves  through  the  open  gauge  line. 4. Close the discharge gauge line and open the discharge  line  stop  valve. 5.   Remove   all   oil   from   the   exterior   of   the compressor. 6.    Test  the  compressor  joints  for  leakage  using  the halide  leak  detector. 5-5