TM 5-3895-383-24 3. Locate the cloud point of the lighter fuel on the right side of the table.  Mark the point on the table. 4. Draw    a    line    between    the    two    points    that    were established.  Label this line "A". 5. Determine  the  lowest  outside  temperature  for  machine operation.  Find this point on the left side of the table. Mark this point.  Draw a horizontal line from this point. Stop  the  line  at  the  intersection  of  line  "A".    Label  this new line "C". 6. Draw a vertical line from the intersection of lines "A" and "C".  Stop the line at the bottom of the table.  Label this line "B".  The point at the bottom of line "B" reveals the percentage of lighter fuel that is required to modify the pour point. The above example shows that the blending will require a thirty percent mixture of lighter fuel. Additives are a good method to use in order to lower the pour point  of  a  fuel.    These  additives  are  known  by  the  following names:      pour   depressants,   cold   flow   improvers,   and   wax modifiers.  When the additives are used in a low concentration, the  fuel  will  flow  through  pumps,  lines,  and  hoses.    These additives     must     be     thoroughly     mixed     into     the     fuel     at temperatures that are above the cloud point.  The fuel supplier should   be   contacted   in   order   to   blend   the   fuel   with   the additives.      The   blended   fuel   can   be   delivered   to   your   fuel tanks. Moisture Content Problems with fuel filters can occur at any time.  The cause of the problem can be water in the fuel or moisture in the fuel.  At low  temperatures,  moisture  causes  special  problems.    There are   three   types   of   moisture   in   fuel:      dissolved   moisture (moisture in solution), free and dispersed moisture in the fuel, and free and settled at the bottom of the tank. Most diesel fuels have some dissolved moisture.  Just as the moisture in air, the fuel can only contain a specific maximum amount  of  moisture  at  any  one  temperature.    The  amount becomes less as the temperature is lowered.  For example, a fuel could contain 100 ppm (0.010 percent) of water in solution at 18°C (65°F).  This same fuel can possibly hold only 30 ppm (0.003 percent) at 4°C (40°F). After the fuel has absorbed the maximum possible amount of water,  the  additional  water  will  be  free  and  dispersed.    Free and   dispersed   moisture   is   fine   droplets   of   water   that   is suspended in the fuel.  Since the water is heavier than the fuel, the water will slowly become free and settled at the bottom of the  tank.    In  the  above  example,  when  the  fuel  temperature was lowered from 18°C (65°F) to 4°C (40°F), 70 ppm of water became free and dispersed in the fuel. The  small  drops  of  water  cause  a  cloudy  appearance  in  the fuel.  If the change in temperature is slow, the small drops of water  can  settle  to  the  bottom  of  the  tank.    When  the  fuel temperature  is  lowered  rapidly  to  freezing  temperature,  the moisture   that   comes   out-of-solution   changes   to   very   fine particles of ice instead of small drops of water. The particles of ice are lighter than the fuel, and the particles of ice will not settle to the bottom of the tank.  When this type of moisture  is  mixed  in  the  fuel,  this  moisture  will  fill  the  fuel filters.  The ice crystals will plug the fuel filters in the same way as wax plugs the fuel filters. If  a  filter  is  plugged  and  fuel  flow  is  stopped,  perform  the following procedure to determine the cause: 1. Remove the fuel filters. 2. Cut the fuel filters open. 3. Inspect   the   fuel   filter   before   the   filter   warms.      This inspection will show that the filter is filled with particles of either ice or wax. The moisture which is free and settled at the bottom of the tank can  become  mixed  with  the  fuel.    The  force  of  any  pumping action  will  mix  the  moisture  with  the  fuel  whenever  fuel  is transferred.  This moisture then becomes free and dispersed water.  This moisture can cause ice in the filters.  This moisture can   cause   other   problems   with   filters   at   any   temperature. Generally, the same force that mixes the water into the fuel will also  mix  dirt  and  rust  from  the  bottom  of  the  tank  with  the water.  The result is a dirty mixture of fuel and water which can also fill the filters and stop fuel flow. Maintenance Section Fuel Specifications 1-37