Calculating Total Required Valve closing torque for Butterfly Valve

[Ryan DelaCourt]

What calculation do most people use to determine rough figures for the closing Torque on triple offset butterfly valves?

From what I have found There are primarily three areas to consider:

1) Disc sealing Torque due to friction,
2) Bearing Torque due to friction ,
3) Hydro static Torque.

I have built a calculator on excel and i have reasonable numbers all throughout the range, however the smaller sizes I have generated are not what I would like them to be (I am comparing my calculated values with our current torque values).

My main issue at this moment in time is defining the Disc Coefficient contact. Could I use a simple steel on steel coefficient such as 0.5 (DRY STATIC) or prehaps I need to consider a sliding value of 0.45 (DRY SLIDING).

I know industries would often conduct tests to determine required contact between the two sealing surfaces but is there a way that I could account for this through a calculation?

Thank You

Ryan

 

[pmover]

valve manufacturers typically provide torque requirements; contact the mfg. without mfg data, guess work applies or conduct torque measurement tests yourself.

good luck!
-pmover

 

[Ryan DelaCourt]

Thank you pmover, I will have a chat with my guys and see if i can organise some testing. Its all good carrying out these calculations to determine values however without testing, it is pointless.