TM  5-3895-374-24-2 result in failure of the valve itself.  If blower capacity appears to be  too  low.    refer  to  the  TROUBLE  SHOOTING  CHECKLIST first.    If  no  help  is  found  there  it  may  be  possible  to  increase the blower speed.  Before attempting this change.  contact the nearest   Distributor   for   recommendations.      Be   prepared   to furnish     data     on     actual     air     requirements     and     operating pressure/temperature conditions. SAFETY PRECAUTIONS For   equipment   covered   specifically   or   indirectly   in   this instruction   book,   it   is   important   that   all   personnel   observe safety precautions to minimize the  chances  of  injury.    Among many   considerations.      the   following   should   particularly   be noted: n Blower  casing  and  associated  piping  or  accessories  may become hot enough to cause major skin burns on contact. n Internal   and   external   rotating   parts   of   the   blower   and driving  equipment  can  produce  serious  physical  injuries. Do  not  reach  into  any  opening  in  the  blower  while  it  is operating,  or  while  subject  to  accidental  starting.    Cover external moving parts with adequate guards. n Disconnect    power    before    doing    any    work    and    avoid bypassing or rendering inoperative any safety or protective devices. n If   blower   is   operated   with   piping   disconnected,   place   a strong  coarse  screen  over  the  inlet  and  avoid  standing  in the discharge air stream. n Stay  clear  of  open  inlet  piping  (suction  area)  of  pressure blowers,    and    the    open    discharge    blast    from    vacuum blowers. n Stay clear of the blast from  pressure  relief  valves  and  the suction area of vacuum relief valves. n Avoid  extended  exposure  in  close  proximity  to  machinery which exceeds safe noise levels. n Use  proper  care  and  good  procedures  in  handling,  lifting, installing, operating and maintaining the equipment. n Casing pressure must not exceed 25 PSI 0l72 kPa) gauge. Do not pressurize vented cavities from an external source, nor restrict the vents. n Do not use air blowers on explosive or hazardous gases. n Other  potential  hazards  to  safety  may  also  be  associated with operation of this equipment.  All personnel working in or  passing  through  the  area  should  be  warned  by  signs and trained to exercise adequate general safety precautions. MAINTENANCE & REPLACEMENTS A   good   program   of   inspection   and   maintenance   servicing, followed consistently, is the most reliable method of minimizing repairs to a blower.  A simple record of services and dates will help  keep  this   work   on   a   regular   schedule.      Basic   service needs  are  lubrication.    checking  for  hot  spots  or  increase  in vibration  and  noise  and  the  recording  of  operating  pressures and  temperatures.    Above  all.    a  blower  must  be  operated within  its  specified  rating  limits,  to  obtain  satisfactory  service life. A newly installed  blower  should  be  checked  frequently  during the first month of full-time operation.  Attention thereafter may be  less  frequent.    depending  on  what  the  early  checks  have shown. Lubrication is normally the most important consideration.      Unless   operating   conditions   are   unusually severe,   a   weekly   check   of   oil   levels   in   the   gearbox,   with addition of oil as required.  should be sufficient.  Complete oil changes should be made at intervals of 1000 operating hours, or more frequently if oil condition becomes poor. Driver  lubrication  practices  should  be  in  accordance  with  the manufacturer’s  instructions.    If  direct  connected  to  the  blower through  a  lubricated  type  coupling.    the  coupling  should  be checked  and  greased  each  time  blower  oil  is  changed.    This will help reduce wear and prevent it from causing vibration.  In a  belted  drive  system.    check  belt  tension  periodically   and inspect   for   frayed   or   cracked   belts.      Refer   to   tensioning instructions under INSTALLATION. In  a  new  and  properly  installed  blower  there  are  no  moving contacts  between  the  two  impellers.    or  between  the  impeller and   cylinder   or   headplates.      Wear   is   then   confined   to   the bearing  which  support  and  locate  the  shafts,  the  shaft  seals, and  the  timing  gears.    All  are  lubricated,  and  wear  should  be nominal  if  clean  oil  of  the  correct  grade  is  always  supplied. Seals  are  subject  to  deterioration  as  well  as  wear,  and  may require replacement at varying periods. Shaft bearings have been selected to have optimum life under average conditions with proper lubrication.  They are critical in the service life of the blower.  Gradual bearing wear may allow a   shaft   position   to   change   slightly.      until   rubbing   develops between impeller and cylinder headplate.  This will cause spot heating,   which   can   be   detected   by   feeling   these   surfaces. Sudden  bearing  failure  is  usually  more  serious.    Since   the shaft   and   impeller   are   no   longer   supported   and   properly located,  extensive  general  damage  to  the  blower  casing  and gears is likely to occur. Shaft  seals  should  be  considered  expendable  items.    to  be replaced  whenever  drainage  from  the  headplate  vent  cavity becomes  excessive  or  when  the  blower  is  disassembled  for any reason.  Sealing effectiveness can vary considerably from seal  to  seal  and  is  also  affected  by  shaft  smoothness  under the  seal  lip.    Because  of  these  normal  variables,  minor  seal leakage    should    not    be    considered    an    indicator    for    seal replacement. Timing   gear   wear.      when   correct   lubrication   is   maintained should be negligible over a period of years.  Gear teeth are cut to provide the correct amount of backlash, and gears correctly mounted on the shafts will accommodate page 3-809