Need to coralate C o F of valve seat material to torque 3

[soupboy]

Is there a means or standard test that can realibly predict actuation torque for soft seated valve materials using the coefficent of friction value of a specific material?

Or is there a defined test that one could use to "sort" soft seated valve materials besides builing several valves from each material and preforming torque test on them?

Soupboy

 

[btrueblood]

Certainly the COF of the seal materials will play a part in determining the actuation torque for a valve.

But, so does the design of the seat/seal - seal preload, which depends on the modulus of the materials, and pressure loading if any, which depends on shutoff conditions and rigidity/fixity of the seal members, also play a part in determining what the "normal force" is that generates friction. Also any designed-in imbalance of pressure forces tending to hold a valve in the closed position.

 

[Sweguy]

My experience is that it is very difficult to get an precise result. It is so many things that affect the torque. Make equations that you think will be correspond with your valve, then you can make a real test and with help of that you can calibrate the friction coefficient for the different surfaces.
After that you can use the equations on other valve sizes and get values that are quite relevant.

 

[FACS]

Maybe:
Can you do an incline plane test to determine the COF?

Once you have an angle on the incline plane, can you interpolate the force required to move the part?

If you know the force, can you use that to determine the torque?

Charlie

http://www.facsco.com

 

[Tmoose]

For coefficient of friction to have much meaning I think the loading needs to create comparable contact pressure and the surfaces must be similar.
- More than a few thousand PSI and some stainless galls CF = real high
- If soft materials means elastomers etc then COF > 1 is pretty possible (witness the anecdotal stories of near disbelief when 1/4 mile drag strip speeds exceeded 200 mph ). The normal force of a test sled on an Inclined plane > 45 degrees vs gravitational force is varying a bit as the angle changes
Might be easier to test a few valves