foreword ... This   descriptive   guidebook   will   familiarize   you   with COMMERCIAL  Model  15H  single  and  tandem  pumps and motors - their component parts - relative position of each part - proper methods for assembly or disassembly of  units  -  care  and  use  of  .these  oil  hydraulic  units  so that better performance and greater life expectancy will result for your benefit. A photographic presentation with explanatory notes covers  the  steps  that  should  be  closely  followed  when servicing    the    elements    that    comprise    these    units. Before any work is done in the repair of these units.  it is suggested that all of the steps used in tearing down the assembled unit and all of the steps used in building up the unit be read.  Such a digest will familiarize you with the general procedure of the work to be done and give you the feel of the specific operations involved. general instructions ... Here   you   .have   a   gear   type   fixed   displacement   oil hydraulic  pump  or  motor  which  has  been  built  to  very high  standards  and  a  new  design.    The  result  is  the Model 15H pump and motor having operating characteristics  far  superior  to  other  pumps  and  motors of its type.  Close fits and small running tolerances were originally    built    in    to    insure    peak    performance    and highest operating efficiency. Slippage  is  a  factor  which  has  considerable  bearing  on the performance.  As the amount of slippage is reduced, the higher the operating efficiency.  Best results develop when  a  close  fit  is  made  between  the  gears  and  all surfaces  they  come  in  contact  with.    Allowance  of  a minimum running clearance is, of course, necessary. Inspection of all COMMERCIAL pumps and motors will disclose gears in matched pairs-all are original equipment,  made  by  COMMERCIAL  on  specially  built machines   which   produce   surfaces   within   limits   much closer than is standard practice. Seldom   should   you   find   it   necessary   to   service   the Model  15H  oil  hydraulic  pump  or  motor  during  its  life expectancy, but should a noticeable drop in performance occur it is advisable to make an inspection and   replace   such   part   or   components   which,   due   to some    unusual    condition,    may    have    become    worn. Should you find it advisable to replace the gears, insist that  they  be  in  matched  pairs  and  the  product  of  the original   manufacturer.      Matched   gears   are   the   very vitals of the gear type pump or motor.  Expendable parts such  as  "0"  ring  shaft  seals,  pocket  seals,  single  and double-lip  oil  seals  and  back-up  rings  should  never  be re-used  even  though  inspection  may  show  these  items as   being   serviceable   for   future   use.      Such   parts   for replacement are available at a cost which is insignificant in  view  of  your  investment  and  when  you  consider  the vital  function  of  these  items  is  to  prevent  leakage.    All replacement parts should be given your final inspection to insure that no damage has resulted after final factory inspection was made. lubrication ... All parts of the units with the exception of the outboard bearing are lubricated by the hydraulic oil in the circuit. Particular  attention  must  be  paid  to  keep  the  oil  in  the circuit  system  clean.    Whenever  there  is  a  pump  or motor   failure   and   there   is   reason   to   feel   that   metal particles may be in the system.  the oil must be drained, the  entire  system  flushed  clean,  and  any  filter  screens thoroughly cleaned.  New oil should be supplied for the entire system.  Oil suitable and recommended for use in circuits  involving  Model  15H  pumps  and  motors  should meet the following specifications: Hydraulic oils should have a viscosity index of 90 or   higher   and   a   viscosity   SUS   150   to   200   at 100°F.  Aniline point should be 165 or higher.  Oil operating temperatures should not exceed 200°F. Oil    should    have    anti-foam    and    anti-oxidation additives. Do    not    use    low    viscosity    naphtha    base    oils, aircraft hydraulic fluid, or hydraulic brake fluid. Oil  with  a  low  pour  point  should  be  used  when operation    is    to    be    in    cold,    low    temperature climates. At   regular   intervals   the   outboard   bearing   should   be lubricated.  You are cautioned that not all lubricants are satisfactory    for    proper    lubrication    of    the    outboard bearing.  Results from tests and field operation indicate that     a     lubricant     such     as     Texaco     Starfak     #2     is satisfactory. Commercial Shearing, Inc. 1964 2