Filter/Separator The   filter/separator   is   a   two-stage   unit consisting  of  a  coalescer  stage  and  a  separator stage  within  a  single  housing.  Each  stage  is  made up of replaceable elements, the number of which is   determined   by   such   considerations   as   the capacity  of  the  elements  in  gallons  per  minute (gpm) and the elements dirt retaining properties. Coalescer  elements  filter  solids  from  the  fluid  and cause  small  particles  of  undissolved  water  to combine  (coalesce)  into  larger  drops  of  water  that, because  of  their  weight,  will  settle  in  the filter/separator   sump.   Separator   elements   are provided  to  remove  any  remaining  free  water  that has not coalesced. Water that accumulates in the filter/separator sump is removed through a drain line,  either  automatically  or  manually. In-Line or Cone Filter In-line  or  cone  filters  have  conical-shaped  fine mesh  screen  or  perforated  metal  sheet  that  is inserted into the system pipe and secured by a set of   flanges.   Its   system   application   determines whether it is considered a filter or strainer. It is most commonly used in seawater systems, where it  is  considered  a  strainer.  This  type  of  filter  is prohibited  in  fuel  systems. MAINTENANCE Proper  operation  of  filters,  strainers,  and  filter separators  is  essential  for  satisfactory  gas  turbine and diesel engine performance. Besides clogging the   systems   with   foreign   matter,   continued operation  with  unfiltered  fluids  results  in accelerated pump wear and system degradation. Routine  maintenance  of  filters,  strainers,  and filter/separators is adequately covered in NSTM, Chapter 541, “Petroleum Fuel Stowage, Use, and Testing,” paragraphs 541-8.51 through 541-8.59. PIPING The  control  and  application  of  fluid  power would be impossible without a suitable means of conveying the fluid from the power source to the point  of  application.  Fluid  lines  used  for  this purpose  are  called  piping.  They  must  be  designed and  installed  with  the  same  care  applicable  to other  components  of  the  system.  To  obtain  this desired  result,  attention  must  be  given  to  the various   types,   materials,   and   sizes   of   lines available  for  the  fluid  power  system.  The  different types of lines and their application to fluid power systems  are  described  in  the  first  part  of  this section.  The  last  part  of  this  section  is  devoted to   the   various   connectors   applicable   to   the different  types  of  fluid  lines. IDENTIFICATION  OF  PIPING The  three  most  common  lines  used  in  fluid power  systems  are  pipe,  tubing,  and  flexible  hose. They  are  sometimes  referred  to  as  rigid  (pipe), semirigid   (tubing),   and   flexible   piping.   In commercial  usage,  there  is  no  clear  distinction between   piping   and   tubing,   since   the   correct designation for each product is established by the manufacturer.   If   the   manufacturer   calls   its product pipe, it is pipe; if the manufacturer calls it  tubing,  it  is  tubing. In  the  Navy,  however,  a  distinction  is  made between  pipe  and  tubing.  The  distinction  is  based on the method used to determine the size of the product.  There  are  three  important  dimensions of  any  tubular  product—outside  diameter  (OD), inside  diameter  (ID),  and  wall  thickness.  The product is called tubing if its size is identified by actual measured outside diameter and by actual wall  thickness.  The  product  is  called  pipe  if  its size is identified by a nominal dimension and wall thickness. PIPING  MATERIALS The  pipe  and  tubing  used  in  fluid  systems today  are  commonly  made  from  steel,  copper, brass,  aluminum,  and  stainless  steel.  The  hose assemblies  are  constructed  of  rubber  or  Teflon. Each  of  these  materials  has  its  own  distinct advantages or disadvantages, depending upon its application. Figure 9-50.—Types of flexible hose installations and fittings. 9-32