O-rings

[Mike / Wi]

I have a MF 220 Backhoe. I am rebuilding the boom swing cylinder. There are 4 o-rings that seal the 3"OD stainless steel rod. The max pressure is 2200psi. I have my choice of a 70 durometer or a 90 durometer o-ring. The 90 seems to be harder material. There are no specifications available from MF on what kind of o-ring to use. The size is a 3/16 X 3"ID. Any ideas on which one would be better for my application would be appreciated. Thanks in advance for your help.

 

[IH2444]

Here is a link I have, darned if I understand it very wellthough. good luck.

http://efunda.com/designstandards/oring/calc_oring_radial.cfm

 

[Mathias NY]

What material are they made from? Not all materials are created equal.

Definately avoid a Silicone oring, they have awful mechanical properties. The 70 Duro oring may be made of this material.

Viton/HNBR/Buna, are all good to excellent on both mechanical properties and oil resistance. The 90 Duro oring is probably one of these materials.

In general the harder the number, the harder it will be to install, but the less likely to fail in a reciprocating application... assuming it isn't damaged during installation.