What is a ball valve simulator?
A ball valve is a quarter-turn valve: a ball with a hole through it sits in the pipe, and turning the handle lines that hole up with the flow or turns it across to shut the flow off. It is one of the most common valves in plumbing and process piping.
This simulator links the two things people care about most: the handle position and the flow. Drag the opening slider from 0 to 100% and watch the ball rotate while a working point tracks an equal-percentage curve.
Why look inside?
From the outside you only see a handle. Showing the ball and the bore makes clear that the flow passes through a hole, not around the ball, and that only a quarter turn is needed.
Two ideas matter most: the shape of the characteristic curve, and the fact that the very first part of the travel barely changes the flow at all.
1. Turn the handle
The handle is joined to the stem, and the stem is joined to the ball. A quarter turn of the handle, from 0° to 90°, rotates the ball inside the valve body.
2. The bore lines up with the pipe
The bore is the hole through the ball. When the bore points across the pipe the ball blocks the passage and nothing flows; as the ball turns, the bore swings toward the pipe and opens a path.
3. An equal-percentage curve starts slowly
A ball valve does not open linearly. Over the first part of its travel the flow rises only a little, which is why a barely-cracked valve still passes very little water.
4. Flow climbs steeply
Past the cracked range the same turn of the handle now adds a much larger share of the flow. This steep rise is what the curve on the right shows between roughly 25% and full open.
5. The valve reaches full open
At 90° the bore is fully in line with the pipe. The valve now passes its rated maximum flow and the working point sits at the top end of the curve.
What is a ball valve?
A ball valve is a quarter-turn valve with a rotating ball inside. The ball has a hole through it, and turning the handle lines that hole up with the pipe to open the flow or turns it across the pipe to shut the flow off.
What is the bore?
The bore is the hole drilled straight through the ball. When the bore points along the pipe the valve is wide open; when it points across the pipe the ball blocks the passage and the valve is closed.
Why is the flow curve not a straight line?
A ball valve has an equal-percentage characteristic. The flow changes very little for the first part of the travel and then rises steeply, so plotting flow against opening gives a curve rather than a straight line.
What does equal-percentage mean?
An equal-percentage valve makes the same step in travel produce the same percentage change in flow, not the same amount of flow. That keeps control fine when the valve is nearly closed.
Why does a quarter turn open it fully?
The ball only needs to rotate 90° to swing the bore from fully across the pipe to fully in line with it, so a single quarter turn takes the valve from closed to open.
What is the operating point?
The operating point is the red dot on the chart. It marks the current pair of values: the opening you have set and the flow the valve now passes at that opening.