TM 5-3895-374-24-2 4. Valve  in  suction  line  must  be  fully  open  at  all times.    Close    discharge    valve    before    starting pump   to   prevent   motor   over   loading.      Open discharge   valve   only   after   pump   reaches   full operating speed. 5. Check   pump   speed   and   discharge   head   and adjust     where     required.          Check     pump     for excessive vibrations. B - During Operation The following should be checked during pump operation: 1. Discharge head 2. Bearing temperature; 212°F (100°C) maximum. 3.    Air  flow  from  motor  over  bearing  housing  if  a TEFC motor is used. 4.    Check pump for excessive vibration. C - Shut Down 1.    Close discharge valve.  Do not run pump longer than necessary against closed discharge valve. 2.    Do   not   isolate   pump   by   closing   suction   and discharge valves. SECTION IV - MAINTENANCE A - Bearings SIHI  ZTN  pump  bearings  consist  of  one  outboard grease  lubricated  ball  bearing  and  one  internal  liquid flushed   carbon   sleeve   bearing.      The   ball   bearing   is lubricated   at   the   factory   for   initial   operation.      After approximately  every  1,000  hours  of  operation,  the  ball bearings should be greased.  After approximately 10,000 hours  of  continuous  operation  or  after  two  (2)  years  of intermittent operation, it is recommended to remove the ball bearing and clean and regrease the bearing.  Under severe  operating  conditions,  the  above  intervals  should be shortened.  Use only high temperature grease with a dropping point over 338°F (170°C) such as: - Shell - Aero Grease No.  16 - Esso - Unirex N3 - Dow - Molykote BR2 - Plus - Or equivalent Mixing noncompatible types of grease may cause a bearing   lubrication   problem   resulting   in   a   premature failure  The  liquid  lubricated  sleeve  bearing  requires  no maintenance.    Abrasives  suspended  in  the  liquid  affect the life of the sleeve bearing. B - Shaft Sealing The shaft sealing is obtained through the use of viton seal   rings.      The   shaft   sealing   does   not   require   any maintenance.    Under  normal  operating  conditions,  the shaft  seal  rings  have  a  minimum  expected  life  of  one year.    Most  pumps  do  not  show  inadmissable  leakage even   after   several   years   of   operation,   the   maximum admissible leakage is considered one drop per minute. In   the   event   of   seal   ring   leakage,   the   medium pumped   will   be   confined   in   the   drainage   chamber between the seal housing and ball bearing.  Leakage, if any,  can  be  drained  from  this  chamber  through  lower tapped hole without any loss of liquid.   DO  NOT  PLUG LOWER TAPPED HOLE The  life  of  the  shaft  seal  rings  is  affected  by  the following factors: 1.    Operation   without   initial   venting,   for   venting procedure refer to Section III, Paragraph A-3. 2.    Failure to pack seal rings with high temperature grease, refer to Section VI, Paragraph C-3. 3.    Use of contaminated heat transfer oil. 4.    Operation above maximum recomended temperature for extended periods. 5.    Controlling pump operation from suction side. 6.    An  in-rush  of  air  through  the  seal  rings  when pump  is  subject  to  negative  pressure.    If  this occurs, pump must be vented before start-up To   prevent   failure   caused   by   an   in-rush   of   air, observe the following precautions: 1.    When  shutting  down  pumps,  do  not  isolate  the pumps  by  closing  both  suction  and  discharge isolating  valves.    As  heat  transfer  oil  cools,  the volume   can   be   reduced   up   to   30%.      The reduction in volume causes an in-rush of air into the pump through the seal rings. 2.    For  installations  with  constant  negative  suction pressure, the cavity between the seal rings  and ball bearing may be flooded with oil to prevent air from  entering  the  pump.    This  is  accomplished by plugging the drain connection and installing a constant oiler at the upper tapped connection. C - Removal of Ball Bearing and/or Seal Rings The removal of the ball bearing and/or seal rings will necessitate   the   disassembly   of   the   pump.      Refer   to Section   VI   -    Disassembly/Assembly    Instructions    for complete  details  in  the  removal  of  these  components. The   following   paragraphs   deal   specifically   with   the removal and installation of the ball bearing (230) and/or seal rings (400). Ball Bearing (Item 230) Section VI, Paragraph A-1 to 6; B-1 to 7; D-1 to 7. Seal Rings (Item 400) Section VI, Paragraph A-1 to 6; B-1 to 7; C-2 to 4; D-3 to 7 D - Driver & Accessories Maintenance and lubrication for driver and accessories   shall   be   to   the   manfacturer's   standard procedures. (page-3 - 1144)