## Ball Valve Torque Calculation Formula

## Ball Valve Torque Calculation Formula

(OP)

Is anyone aware of any empirical formula to calculate the torque of a ball valve? There are formulae like Roark's to find MAST but how can we mathematically compute the Break to Open, End to Open torque values for a valve??

## RE: Ball Valve Torque Calculation Formula

## RE: Ball Valve Torque Calculation Formula

Usually torque is a measured value under known and optimal/ideal conditions.

For a single ball valve experienced torque can vary from an observed ideal torque up to about double or triple value over time.

This is the reason that reliable producers set a limits for operational values when giving out a torque value.

Non ideal conditions, abrasion, stickiness and residues, maintenance and operational metodes, pressure, flow etc. can give a multitude of higher values. Five or ten times higher torque than ideal is not unheard of, but indicates that another type of valve should be selected, or operational data and maintenance should be improved.

When selecting electrical actuators it is recommended both to give as long operational time as possible to give a smaller actuator. On the other hand it is generally recommended (especially for larger valves) to leave enough time to eventually add an extra 1:2 gear to double the time and output force, if it should be proven to be necessary.

Conclusion: Calculation of torque is done, but based on practical observed data and conditions for some valves in a range, given known data for fluid and flow.

## RE: Ball Valve Torque Calculation Formula

For actuator sizing I always use the full differential pressure for the given ANSI class of the valve plus a safety factor.

## RE: Ball Valve Torque Calculation Formula

## RE: Ball Valve Torque Calculation Formula

## RE: Ball Valve Torque Calculation Formula

As you can see, there are many variables that affect the required torque. So even if you do develop and equation for your situation, you still should verify by testing. Your estimates for coefficient of friction can easily be off by 100% in a calculation.