Table 5-1.—Wall Thickness Schedule Designations for Pipe 160 pipe has a 0.815 ID. In each case the OD is 1.315  (table  5-1)  and  the  wall  thicknesses  are 0.133 0.179 and  0.250 respectively.   Note that  the  difference  between  the  OD  and  ID includes  two  wall  thicknesses  and  must  be  divided by  2  to  obtain  the  wall  thickness. Tubing  differs  from  pipe  in  its  size  classi- fication.  Tubing  is  designated  by  its  actual  OD. (See table 5-2.) Thus, 5/8-inch tubing has an OD of  5/8  inch.  As  indicated  in  the  table,  tubing  is available  in  a  variety  of  wall  thicknesses.  The diameter  of  tubing  is  often  measured  and indicated in 16ths. Thus, No. 6 tubing is 6/16 or 3/8  inch,  No.  8  tubing  is  8/16  or  1/2  inch,  and so  forth. The  wall  thickness,  material  used,  and  ID determine the bursting pressure of a line or fitting. The greater the wall thickness in relation to the ID  and  the  stronger  the  metal,  the  higher  the bursting  pressure.  However,  the  greater  the  ID  for a  given  wall  thickness,  the  lower  the  bursting pressure, because force is the product of area and pressure. Materials The  pipe  and  tubing  used  in  fluid  power systems are commonly made from steel, copper, brass, aluminum, and stainless steel. Each of these metals  has  its  own  distinct  advantages  or disadvantages  in  certain  applications. Steel pipe and tubing are relatively inexpensive and are used in many hydraulic and pneumatic systems.  Steel  is  used  because  of  its  strength, suitability   for   bending   and   flanging,   and adaptability to high pressures and temperatures. Its  chief  disadvantage  is  its  comparatively  low resistance  to  corrosion. Copper pipe and tubing are sometimes used for fluid power lines. Copper has high resistance to corrosion and is easily drawn or bent. However, it  is  unsatisfactory  for  high  temperatures  and  has a  tendency  to  harden  and  break  due  to  stress  and vibration. Aluminum has many of the characteristics and qualities required for fluid power lines. It has high resistance to corrosion and is easily drawn or bent. In addition, it has the outstanding characteristic of  light  weight.  Since  weight  elimination  is  a  vital factor  in  the  design  of  aircraft,  aluminum  alloy tubing  is  used  in  the  majority  of  aircraft  fluid power  systems. Stainless-steel tubing is used in certain areas of many aircraft fluid power systems. As a general rule, exposed lines and lines subject to abrasion or intense heat are made of stainless steel. An  improperly  piped  system  can  lead  to serious  power  loss  and  possible  harmful  fluid 5-2