A second o ring may be used for the wiper but it must not actually seal because a pressure trap condition is likely to develop between two reciprocating o ring seals.
O ring running friction.
Running friction high running friction may cause difficulty by wearing soft metal parts.
The improvement in break out friction with a chlorinated o ring or seal is negligible but a chlorinated o ring can be used in combination with external.
The axial friction maximum friction stress and maximum contact stress of the o ring are analysed using finite element method as the confining pressure varying from 50 to 300 kpa.
This is especially true if high pressures are involved.
Metals such as copper brass aluminum can be rapidly worn away by a moving o ring.
In addition to the usual causes of running friction.
Since this can easily be forgotten it is preferable to provide a vent hole between the two o rings.
If unexplained leakage occurs with these or other soft metals it is good practice to check the metal dimensions for.
High running friction may cause difficulty by wearing soft metal parts.
This can be prevented by cutting the outer o ring so it cannot seal.