Technical  Directive  for  Piping  Devices  and Flexible  Hose  Assemblies,  NAVSEA   S6430-AE- TED-010. volume 1. provide detailed instructions on  discarding  and  downgrading  of  rubber  hoses exceeding  their  shelf  life. PFTE 1Q89 or the first Figure  5-10.—Hose identification. 1/89  means  the  hose  was  made  during quarter  (1  Jan  to  31  Mar)  of  1989. The cure date limits the length of time a rubber hose  can  be  stored,  in  bulk  or  as  an  assembly, prior to being placed into service. The storage or shelf life for rubber hose is 4 years. For the hose manufactured  in  1Q89,  the  storage  or  shelf  life will end on the 31st of March 1993. At this point, the  hose  is  no  longer  considered  usable  and  should be discarded or downgraded. The  Aviation  Hose and  Tube  Manual,  NAVAIR  01-1A-20,  and  the 5-9 PFTE hose is a flexible hose designed to meet the requirements of higher operating pressures and temperatures  in  present  fluid  power  systems.  This type of hose is made from a chemical resin, which is processed and extruded into a tube shaped to a desired size. It is reinforced with one or more layers of braided stainless-steel wire or with an even number of spiral wrap layers with an outer wire  braid  layer. PTFE  hose  is  unaffected  by  all  fluids  presently used in fluid power systems. It is inert to acids, both  concentrated  and  diluted.  Certain  PFTE hose  may  be  used  in  systems  where  operating temperatures  range  from  –100°F  to  +500°F. PTFE  is  nonflammable;  however,  where  the possibility of open flame exists, a special asbestos fire  sleeve  should  be  used. PFTE  hose  will  not  absorb  moisture.  This, together  with  its  chemical  inertness  and  anti- adhesive  characteristics,  makes  it  ideal  for  missile fluid  power  systems  where  noncontamination  and cleanliness are essential. In  lieu  of  layline  marking,  PTFE  hoses  are identified by metal or pliable plastic bands at their ends and at intervals along their length. Figure 5-10, view C, shows a hose label for a PTFE hose. Usually the only condition that will shorten the life  of  PTFE  hose  is  excessive  temperature.  For this  reason  there  is  no  manufacture  date  listed  on the  identification  tag. APPLICATION As  mentioned  earlier,  flexible  hose  is  available in three pressure ranges: low, medium, and high. When  replacing  hoses,  it  is  important  to  ensure that the replacement hose is a duplicate of the one removed   in   length,   OD,   material,   type   and contour,  and  associated  markings.  In  selecting hose, several precautions must be observed. The selected hose must 1. 2. be  compatible  with  the  system  fluid, have a rated pressure greater than the design pressure  of  the  system,