Rubber Swell due to Gear oils

Where gear  oils  are  in  contact  with  rubber gaskets, seals, etc., the  action of  the  fluid on the  rubber compositions is of  importance. Consequently a Federal Test Method, 3604-T, has been set up. Such a test  can  be  varied as to  temperature, time and the  polymer     composition tested  depending upon  the    actual  service conditions of the  gear oil.

Thus, for ATF the following procedure is used. Sections of piston seals made from Acadia 3612 rubber compound are subjected to hot transmission fluid. Measurements of volume and hardness are made before and after the test. Two  seals are  cut  into  eight  sections each  and  the  sections  are  suspended  in  test  tubes  containing the lubricant and  held in a bath  at  300 degree F for  70  hours. The  sections are  then  cooled for  thirty  minutes  to  one hour in a  fresh  portion of the  test  fluid maintained at room  temperature. After wiping dry, the final volume and durometer readings are taken.

Prevention of Contamination of Gear Lubricants

Gear sets operate under such varied conditions that it is difficult to give general suggestions for prevention of contamination of the gear lubricant. The two contaminants most often encountered are water and dust. In the latter are included large particles such as scale in steel mills. Less trouble is encountered where a circulating  system  provides  the  lubricant  rather  than  a  splash system, since the former  can  be  supplied  with settling  tanks  or filters. Even here regular inspection is necessary and accumulated water should be drawn off whenever noted. Such accumulations may  be quite  large  in the case of  gear  oils  for  ship  propellers or in oils servicing  paper  mill  machinery  or steel  mill  gears.

Where  gear cases  are  vented, the location  of the vent or a pipe  connection to the  same  should  be so  located  that  the least  dirt  possible  can enter. One automobile  manufacturer reduced  contamination in  differential cases by  extending  a  line  from  the  vent  and  securing  it  forward  under  the  car  frame  with  the  opening  toward  the  side  of  the  vehicle.

Prevention of contamination of lubricants by chemicals must have individual consideration. In  extreme  cases it  may  be  necessary  to  provide  pressure  on  gear  cases to  prevent  entry  of contaminants.