Ball valve

How much do I need to turn the lever to cut off 50% of water flow in 2" copper pipe?

1) exactly turn half between Full open and Full close position?

or

2) 10% more towards close-side than half position?

or

3) 10% less toward open-side than half position?

as you know, the shape of ball in the pipe rotate to open and close, so if turn middle, then how much it actually shut-off?

Thanks

flow

The closing of the valve is not linear, and since it should NOT be closed 1/2 way, I doubt that anyone has studied it. But closed is probably the same as full open. As for half closed, it would depend on what the flow is whether there was any reduction, or if turbulence would cause more than a 50 % reduction.

1/2 the pressure does not equal 1/2 of the flow. The valve will be close (but not exactly) to a sharp edge orifice, so the flow will be related to the pressure in a square root relationship. Probably not worth trying to figure out for a ball valve. Ball valves are not very good metering valves, and should be full open or completely closed.