The name of the service and destination should be painted on by stencil or hand lettering, or by application  of  previously  printed,  stenciled,  or lettered  adhesive-backed  tape.  Lettering  will  be 1 inch high for a 2-inch or larger OD bare pipe or  insulation.  For  smaller  sizes,  lettering  size  may be  reduced  or  label  plates  attached  by  wire  or other suitable means. Direction   of   flow   will   be   indicated   by   an arrow 3 inches long pointing away from the let- tering. For reversible flow, arrows are to be shown on  each  end  of  the  lettering. Black   is   used   for   lettering   and   arrows. However, on dark-colored pipe (including oxygen piping),  white  is  used. Markings   will   be   applied   to   piping   in conspicuous   locations,   preferably   near   the control valves and at suitable intervals so every line will have at least one identification marking in  each  compartment  through  which  it  passes. Piping in cabins and officers’ wardrooms will not normally  be  marked. PACKING  AND  GASKET MATERIAL Packing and gasket materials are required to seal joints in steam, water, gas, air, oil, and other lines and to seal connections that slide or rotate under  normal  operating  conditions.  There  are many  types  and  forms  of  packing  and  gasket materials  available  commercially. PACKING  AND  GASKET  SELECTION To simplify the selection of packing and gasket materials  commonly  used  in  naval  service,  the Naval  Sea  Systems  Command  has  prepared  a packing and gasket chart, Mechanical Standard Drawing  B-153.  It  shows  the  symbol  numbers  and the  recommended  applications  for  all  types  and kinds  of  packing  and  gasket  materials. The symbol number used to identify each type of  packing  and  gasket  has  a  four-digit  number. The  first  digit  shows  the  class  of  service  with respect  to  fixed  and  moving  joints;  the  numeral 1 shows a moving joint (moving rods, shafts, valve stems),  and  the  numeral  2  shows  a  fixed  joint (flanges,  bonnets).  The  second  digit  shows  the material  of  which  the  packing  or  gasket  is primarily  composed—asbestos,  vegetable  fibre, rubber, metal, and so forth. The third and fourth digits  show  the  different  styles  or  forms  of  the packing  or  gasket  made  from  the  material. Practically all shipboard packing and gasket problems   can   be   solved   by   selection   of   the correct material from the listings on the packing and  gasket  chart.  The  following  examples  show the kind of information that you can get from the packing  and  gasket  chart. Suppose  you  are  required  to  repack  and install a valve in a 150-psi seawater service system. Under  the  subhead  Symbols  and  Specifications for  Equipments,  Piping  and  Independent  Systems, you  find  that  symbol  1103  indicates  a  suitable material for repacking the valve. Notice that the first  digit  is  the  numeral  1,  indicating  that  the material is for use in a moving joint. Under the List  of  Materials,  you  find  the  packing  is  asbestos rod,   braided. For   installing   the   valve,   you   need   proper gaskets. By use of the same subhead, you find that symbols 2150, 2151 type II, 2152, and 2290 type II are all suitable for installing the valve. Notice that the first digit is the numeral 2, which indicates that  it  is  designed  for  fixed  joints.  Again,  by referring   to   the   List   of   Materials,   you   can determine  the  composition  of  the  gasket. Besides  the  Naval  Ship  Systems  Command drawing,  most  ships  have  a  packing  and  gasket chart  made  up  specifically  for  each  ship.  The  ship- board  chart  shows  the  symbol  numbers  and  the sizes of packing and gaskets required in the ship’s piping  system,  machinery,  and  hull  fittings. PACKING  OF  MOVING  JOINTS Valves  are  components  used  to  control  the transfer   of   liquids   and   gases   through   fluid piping  systems.  Most  valves  have  moving  joints between  the  valve  stem  and  the  bonnet.  When fluid  is  on  one  or  both  sides  of  a  moving  joint, the joint may leak. Sealing the joint prevents this leakage.   Sealing   a   moving   joint   presents   a problem  because  the  seal  must  be  tight  enough to  prevent  leakage,  yet  loose  enough  to  let  the valve stem turn without binding. Packing is the most common method of sealing a moving joint. Packing  is  a  sealing  method  that  uses  bulk material (packing) that is reshaped by compression 9-41