Ocillating O-ring friction

[EngForm78]

I am trying to determine the friction created by an O-ring seal in an ocillating application. The application is like that of a facet handle where motion is limited to about 90 degrees. The result will be the force required to turn the valve handle. I have found equations for fiction in recipricating applications, like pistons, in the Parker O-Ring handbook, but nothing for the ocillating motion. Any suggestions on how this can be done.

Thanks

EngForm78

 

[israelkk]

First off all you should look for the torque needed to rorate the valve handle and not the force. The torque is constant while the force depends on the valve handle length and where you apply the force along the handle.

If you can control the o-ring compression (in % of the wire diameter) as recommended in Parker catalog then you can estimate the torque. But, be aware that the starting torque can be many times larger than the running torque. After some rest of the handle the first time you rotate the handle the torque will be much higher than the following one.

 

[EngForm78]

Yes, I did mention force because I was thinking in terms of the final answer to my problem. I should be for general- Sorry.

I have looked through the Parker handbook and do not see a torque estimation equation based on %compression. What section did you see this? I understand how compression can affect the torque becasue the increase in compression will increase the friction force. Basically I am looking for an equation that relates to friction between rotating surfaces.

Thanks

 

[israelkk]

The Parker catalog 5700A gives the force as a function of the o-ring wire length unit, % of compression and fluid pressure, in a form of graphs on page 5-9.

The o-ring wire length = o-ring Diamter X pi.

Multiply the calculated force by the ball diameter (if you use 2 o-rings). This will give you the estimated torque. Only actual tests will give accurate results.