TM 5-3895-374-24-2 belt  only  to  the  point  where  its  top  surface  is  even with the bottoms of the other undeflected belts. 6. A new set of belts should be first tensioned about 1/3 greater than normal to allow for stretch and wear-in. Before    putting    the    drive    into    normal    operation, increase  the  tension  as  obtained  above  by  a  small amount.  Recheck after each 8 hour operating period during the first 50 hours, and adjust as necessary. Before   operating   the   drive   under   power   to   check initial  belt  tension,  first  remove  covers  from  the  blower connections.    Make  sure  the  interior  is  still  clean,  then rotate  the  shaft  by  hand.    Place  a  screen  over  the  inlet connection   to   prevent   anything   being   sucked   into   the blower  while  it  is  operating,  and  avoid  standing  in  line with the discharge opening.  Put oil in the gearhouse per instructions under LUBRICATION. Before   connecting   piping,   remove   any   remaining antirust   compound   from   blower   connections.      Piping must be clean and should be sized so that the air velocity will  not  exceed  75  feet  per  second  123  m  per  second). Pipe used should be no smaller than blower connections. In  addition,  make  sure  it  is  free  of  dirt,  scale,  cuttings, weld beads, or foreign materials of any kind. To   further   guard   against   damage   to   the   blower. especially   when   an   inlet   filter   is   not   used,   install   a substantial   screen   of   16   mesh   backed   with   hardware cloth at or near the inlet connections.  Make provisions to clean  this  screen  of  collected  debris  after  a  few  hours operation.  It should be removed when its usefulness has ended,  as  the  wire  will  eventually  deteriorate  and  small pieces going into the blower may cause serious damage. Pipe    threads    or    flanges    must    meet    the    blower connections accurately and squarely.  Do not attempt to correct misalignment by  springing  or  cramping  the  pipe. In   most   cases   this   will   distort   the   blower   casing   and cause  impeller  rubbing.    In  severe  cases  it  can  prevent operation  or  result  in  a  broken  drive  shaft.    For  similar reasons,  piping  should  be  supported  near  the  blower  to eliminate    dead    weight    strains.        Also,    installation    of flexible connectors or expansion joints is recommended. Figure    4    represents    in    diagram    form    a    blower installation    with    all    accessory    items    that    might    be required under various operating conditions.  Inlet piping should    be    completely    free    of    valves    or    restrictions. When  a  shut-off  valve  (not  shown)  cannot  be  avoided, make sure a  full  size  vacuum  relief  is  installed  near  the blower  inlet.    This  will  protect  against  blower  overload caused by accidental closing. Need   for   an   inlet   silencer   will   depend   on   blower speed and pressure, as well as sound-level requirements in  the  general  surroundings.    An  inlet  filter  is  normally recommended, especially in dusty or sandy locations, for blower protection.  A discharge silencer is also normally suggested.    Specific  recommendations  on  silencing  can be   obtained   from   the   nearest   Distributor.      Silencers should be mounted as close to blower as possible. Discharge   piping   requires   a   pressure   relief   valve, and  should  include  a  manual  unloading  valve  to  permit starting  the  blower  under  no-load  conditions.    Reliable pressure/vacuum   gauges   and   good   thermometers   at both   inlet   and   discharge   are   recommended   to   allow making     the     important     checks     on     blower     operating conditions.    If  the  demand  is  constant,  but  somewhat lower  than  the  blower  output,  excess  may  be  blown  off through the manual unloading valve. In   multiple   blower   installations   when   two   or   more units  discharge  into  a  common  header,  use  of  check valves  is  recommended.    These  should  be  of  a  direct acting  or  free  swinging  type,  with  one  valve  located  in each blower Figure 4-Installation with Accessories. discharge    line.        Properly    installed,    they    will    protect against   damage   from   reverse   rotation   caused   by   air backflow through an idle blower. After  piping  is  completed,  and  before  applying  power, rotate the drive shaft by hand again.  If it does not move with  uniform  freedom,  look  for  uneven  mounting,  piping strain, excessive belt tension or coupling misalignment. Do not operate the blower more than briefly  at  this  time because    of    possible    inadequate    oil    supply    in    the gearhouse.  Read LUBRICATION section. LUBRICATION A   simple   but   very   effective   lubrication   system   is employed  on  UNIVERSAL  RAI®  blowers.    At  the  drive shaft   end   the   bearings   are   grease   lubricated   using hydraulic pressure relief fittings.  These relief fittings vent any excess grease, preventing pressure build-up on the seals.    A  restriction  plug  and  metering  orifice  prevent loss of lubricant from initial surges in lubricant pressure but permit venting excess lubricant under steadily rising pressures. The    blind    end    bearings    and    timing    gears    are enclosed by a gearhouse located opposite the drive end of  the  blower.    In  a  side  outlet  blower,  the  lower  timing gear functions as an oil slinger, carrying lubricant to the upper timing gear and providing splash lubrication for the bearings.  Pressure within the gearbox is vented through the breather vent plug 125). The above description also applies in general to the top or bottom outlet style blower, the principal difference being that both gears dip into the oil sump. Before starting blower, be sure oil has been put in gearhouse,  as  ALL  OIL  WAS  DRAINED  FOLLOWING SHOP  TESTS.    For  recommended  lubricating  oil  see Table 2.  Use a good grade industrial type rust, oxidation. and foam inhibited, non-detergent oil. page 3-806