TM 55-4920-328-13 starter  and  contactor  compartment  in  the  control  cab module to supply 208v ac, three-phase electrical power to   the   pump   motor   in   the   oil   system.      The   pump operates to supply turbine lubricating oil to the T53 and T63  engine  through  the  manual  valve  and  40-micron filter.      The   oil   flows   through   the   check   valve   to   the engine  under  test  at  a  pressure  not  to  exceed  2  psig. The   relief   and   bypass   valve,   set   at   35   psig,   allows excess oil in the supply line to return to the oil reservoir. Scavenge  oil  from  the  engine  flows  through  the  heat exchanger and across the temperature probe to a three- position   manual   selector   valve.      The   T74   engine   is provided  with  a  self-contained  oil  system,  but  requires external oil cooling.  The center position of the manual selector valve diverts cooled engine system oil from the heat  exchanger  to  return  to  the  engine  through  the  oil system supply line and 40-micron filter.  The T53 engine position  of  the  manual  selector  valve  allows  scavenge oil to return to the oil reservoir through a back pressure regulating valve set at 55 to 60 psig.  The T63 position of   the   manual   selector   valve   allows   scavenge   oil   to return   to   the   tank   through   a   second   back   pressure regulator  set  at  30  psig.    The  temperature  regulating valve,   actuated   by   the   temperature   probe,   is   set   at 180°F  to  regulate  the  flow  of  cooling  water  through  the heat  exchanger  to  maintain  a  constant  oil  temperature. Engine  gearbox  oil  vapor  returns  to  the  tank  assembly through  another  return  line.    When  the  supply  oil  level drops to a point six inches or less from the bottom of the tank  assembly,  the  fluid  level  transmitter  operates  to complete  a  circuit  to  energize  the  ENGINE  LOW  OIL LEVEL  indicator  DS10  (17,  figure  1-25)  on  the  upper panel of the services sub-module. (8) Portable oil lubricating unit pumping assembly. (a) The portable oil lubricating unit pumping assembly  (figure  1-14),  hereinafter  referred  to  as  the portable oil unit, provides low-pressure lubricating oil for lubrication    of    the    bearings    on    certain    water    brake assemblies.        The    portable    oil    unit    is    an    enclosed assembly (shown schematically in figure 1-15) consisting   of   a   rectangular   oil   tank   (1,   figure   1-14), motor,  supply  pump,  scavenge  pump,  heat  exchanger, and relief valve.  Two pressure gages (4,5), a 10-micron filter, and a flow switch are installed in the pressure line to the supply port.  A pressure switch is also connected to the supply line to provide a low oil pressure warning to the test technician.  The portable oil unit is equipped with  a  combination  oil  tank  cap  and  filter-breather  (2), sight indicator (3), electrical receptacles (6.  9.  12) for Dower and signal circuit connections, oil out and return fittings  (7,8),  and  heat  exchanger  cooling  water  in  and out  fittings  (10,11).    The  motor  is  a  208v  ac,  three- phase,   60   Hz   unit   used   to   simultaneously   drive   the supply and scavenge pumps. (b)  With  system  power  from  the  generator set  available  at  the  control  power  module  (Unit  5),  the INST PWR ON switch S1 (7, figure 1-26) is energized. The   LUBE   PUMP   START   switch   S13   (13)   is   then depressed to energize the coils of the contactors in the starter  and  contactor  compartment  in  the  control  cab module to supply 208v ac, 60 Hz power to operate the motor  and  drive  the  pumps.    The  relief  valve  is  set  to open   at   20   psig   to   bypass   supply   oil   to   the   tank assembly  to  prevent  excessive  pressures  to  the  water brake   bearing.      The   pressure   gages   installed   in   the supply line indicate the amount of pressure drop across the filter.  The differential pressure indicates the amount of  clogging  in  the  filter  and  is  used  as  an  indication  of the  need  for  cleaning.    At  a  flow  above  0.25  gpm,  the normally-closed spat flow switch is in the open position. When the flow rate drops below the specified value, the flow  switch  closes  to  complete  a  circuit  and  illuminate the   WATER   BRAKE   LOW   OIL   FLOW   indicator   DS6 (22, figure 1-25) on the ALARM DISPLAY section of the upper panel in the services sub module and simultaneously  cause  the  audible  alarm  to  sound.    The spat pressure switch is in the normally-closed position at normal  supply  pressures.    When  the  supply  pressure drops  below  a  pre-set  pressure  of  12  to  13  psig,  the switch  actuates  to  complete  a  circuit  to  illuminate  the WATER  BRAKE  LOW  OIL  PRESS  indicator  DS4  (20) on   the   panel   and   simultaneously   cause   the   audible alarm  to  sound.    If  a  warning  light  comes  on  and  the audible  alarm  sounds,  the  LUBE  PUMP  STOP  switch S14 (25, figure 1-26) on the No.  1 power control panel assembly   (32)   is   depressed   to   stop   the   motor   and pumps.        Refer    to    table    1-1    for    additional    leading particulars of the portable oil unit. (9) Test trailer water system. (a)  The  test  trailer  water  system  (figure  1- 16) provides cooling water for METS systems.  The test trailer   water   supply   system   (shown   schematically   in figure    (17)    consists    of    a    series    of    plumbing    lines connected to a 0.125-inch mesh strainer (2, figure 1-16), inlet  control  valve  (15),  75-micron  filter  (5),  two  flow switches (4, 6).  back pressure control valve (13), quick- disconnect   fittings   and   the   T700   water   filter   with   21 changeable  elements,  all  located  below  the  test  trailer deck.  The filter and flow switches control the supply of water to the water brake bearing.  The inlet control valve and  back  pressure  control  valve  are  both  hydraulically 1-18   Change 3