TM 5-3895-374-24-2 started, gradually close the discharge unloading valve to apply working pressure.  At this point it is recommended that a good pressure gauge or manometer be connected into  the  discharge  line  if  not  already  provided.    and  that thermometers    be    in    both    inlet    and    discharge    lines. Readings   from   these   instruments   will   show   whether pressure or temperature  ratings  of  the  blower  are  being exceeded. During   the    final    run,    check    operating    conditions frequently   and   observe    the    oil    levels    at    reasonable intervals.    If  excessive  noise  or  local  heating  develops, shut   down   immediately   and   determine   the   cause.      If either   pressure   rise   or    temperature    rise    across    the blower  exceeds  the  limit  specified  in  this  manual  shut down  and  investigate  conditions  in  the  piping  system  or in the process to which air is being supplied.  Refer to the TROUBLE SHOOTING CHECKLIST for suggestions on various problems that may appear. The blower should now be ready for continuous duty operation  at  full  speed.    During  the  first  few  days  make periodic    checks    to    determine    whether    all    conditions remain   steady,   or   at   least   acceptable.      This   may   be particularly  important  if  the  blower  is  supplying  air  to  a process  system  where  conditions  can  vary.    At  the  first opportunity,   stop   the   blower   and   clean   the   temporary inlet   protective   screen.      If   no   appreciable   amount   of debris has collected, the screen may  be  removed.    See comments  under  INSTALLATION.    At  this  same  time, verify  leveling,  coupling  alignment  or  belt  tension,  and mounting bolt tightness. Should    operating    experience    prove    that    blower capacity is a little too high for the actual air requirements, a  small  excess  may  be  blown  off  continuously  through the  manual  unloading  vent  valve.    Never  rely  on  the pressure relief valve as an automatic vent.  Such use may cause the discharge pressure to become excessive and can also TROUBLESHOOTING CHECKLIST TROUBLE ITEM POSSIBLE CAUSE REMEDY No Air Flow 1 Speed too low Check by tachometer and compare with speed shown on Roots Order Acknowledgment. 2 Wrong rotation Compare actual rotation with Figure 2. Change driver if wrong. 3 Obstruction in piping Check piping, screen, valves.  silencer, to assure an open flow path. Low capacity 4 Speed too low See item 1.  If belt drive, check for slippage and readjust tension. 5 Excessive pressure Check inlet vacuum and discharge pressure, and compare these figures with specified operating conditions on Order. 6 Obstruction in piping See item 3. 7 Excessive slip Check inside of casing for worn or eroded sur- faces causing excessive clearances. Excessive Power 8 Speed too high Check speed and compare with Roots Order Acknowledgment. 9 Pressure too high See item 5. 10 Impellers rubbing Inspect outside of cylinder and headplates for high temperatures areas, then check for-im- peller contacts at these points.  Correct blower mounting, drive alignment. Overheating of 11 Inadequate lubrication Restore correct oil levels in gearbox and Bearings.  or Gears lubricate. 12 Excessive lubrication Check gear oil level.  If incorrect, drain and refill with clean oil of recommended grade. 13 Excessive pressure rise See item 5. 14 Coupling misalignment Check carefully.  Realign if questionable. 15 Excessive belt tension Readjust for correct tension. 16 Speed too low Speeds lower than the minimum recommended will overheat the entire blower. Vibration 17 Misalignment See item 14. 18 Impellers rubbing See item 10. 19 Worn bearings, gears Check gear backlash and condition of bearings. 20 Unbalanced or rubbing Scale or process material may build up on cas- impellers ing and impellers.  or inside impellers.  Remove build-up to restore original clearances and im- peller balance. 21 Driver or blower loose Tighten mounting bolts securely. 22 Piping resonances Determine whether standing wave pressure pulsations are present in the piping.  Refer to Distributors. page 3-808