Figure 5-21.—Ferrules installed on tube, preset and removed for inspection. b.  For  recessed-type  ferrules,  the  leading edge must be snug against the tube OD. Determine this  visually  and  by  attempting  to  rock  the  ferrule on  the  tube. 3. Ensure that the nut end of the ferrule (both types)  is  collapsed  around  the  tube  to  provide support  against  bending  loads  and  vibration. 4. The ferrule (both types) must have little or no play along the direction of the tube run. Check this by trying to move the ferrule back and forth by hand. The ferrule will often be free to rotate on  the  tubing;  this  does  not  affect  its  function. 5. For flush-type ferrules, check that the gap between the raised metal ridge and the cutting end of the ferrule stays the same while the ferrule is rotated.  (Omit  this  check  for  recessed-type  ferrules or if the flush-type ferrule will not rotate on the tube). 6.  Check  that  the  middle  portion  of  the  ferrule (both types) is bowed or sprung into an arc. The leading edge of the ferrule may appear flattened into  a  cone  shape;  this  is  acceptable  as  long  as there  is  a  bowed  section  near  the  middle  of  the ferrule. If the whole leading section of the ferrule is  flattened  into  a  cone  with  no  bowed  section, the ferrule (and possibly the fitting body, if used) has been damaged by overtightening and will not seal reliably. Final  Assembly When  you  make  a  final  assembly  in  the system, use the following installation procedure: 1. Lubricate all threads with a liquid that is compatible with the fluid to be used in the system. 2.  Place  the  tube  assembly  in  position  and check  for  alignment. 3. Tighten the nut by hand until you feel an increase  in  resistance  to  turning.  This  indicates that the sleeve or ferrule pilot has contacted the fitting. 4. If possible, use a torque wrench to tighten flareless  tubing  nuts.  Torque  values  for  specific installations  are  usually  listed  in  the  applicable technical publications. If it is not possible to use a torque wrench, use the following procedures for tightening the nuts: After  the  nut  is  handtight,  turn  the  nut  1/6 turn (one flat on a hex nut) with a wrench. Use a  wrench  on  the  connector  to  prevent  it  from turning  while  tightening  the  nut.  After  you  install the  tube  assembly,  have  the  system  pressure  tested. Should  a  connection  leak,  you  may  tighten  the nut an additional 1/6 turn (making a total of 1/3 turn).  If,  after  tightening  the  nut  a  total  of  1/3 turn, leakage still exists, remove the assembly and inspect  the  components  of  the  assembly  for  scores, cracks,  presence  of  foreign  material,  or  damage from   overtightening. NOTE:  Overtightening  a  flareless-tube  nut drives  the  cutting  edge  of  the  sleeve  or  ferrule deeply  into  the  tube,  causing  the  tube  to  be weakened  to  the  point  where  normal  vibration could cause the tube to shear. After you complete the   inspection   (if   you   do   not   find   any   dis- crepancies),  reassemble  the  connection  and  repeat the pressure test procedures. CAUTION:   Do  not  in  any  case  tighten  the nut  beyond  1/3  turn  (two  flats  on  the  hex  nut); this is the maximum the fitting may be tightened without the possibility of permanently damaging the sleeve or the tube. CONNECTORS  FOR FLEXIBLE  HOSE As  stated  previously,  the  fabrication  of  flexible hose assemblies is covered in applicable training manuals,   technical   publications,   and   NAVAIR 01-1A-20. There are various types of end fittings for both the piping connection side and the hose 5-17