Ball Diameter calculation for ball valve 1

[rocky06]

I want to know whether their is a standard calculation for Ball valve ball diameter selection

As All Parameters in Ball valve Design are Dependent on ball Diameter.

I do know about the thumb rule for ball diameter selection ( approx. 1.5-1.7 times of valve bore)

Is their any justification for this thumb rule,any standard reference?????

 

[MikeHalloran]

Draw a section through the valve centerline, normal to the stem, showing the seats, overlaying the ball in open and closed positions.

It's not a law; it's not a rule; it's geometry.


Mike Halloran
Pembroke Pines, FL, USA

 

[rocky06]

Sir,thank you for your reply

diameter remains same irrespective of valve rating for same valve size?

 

[MikeHalloran]

For a constant bore diameter,
if the seal/seat geometry has to increase,
then the ball size does also.
Seal/seat geometry might change
for pressure
for fire resistance
for extreme temperature service
or just for fun.

There are good commercial reasons to standardize designs,
and good commercial reasons to minimize size/weight,
and good commercial reasons to differentiate products.

So, with a simple geometric exercise, you can guess the minimum ball size you might find for a given bore, but the maximum ball size is not really limited.

I think API publishes standard envelopes for valves, but I don't know if the internals interchange among manufacturers. Outside of the API world, they don't.

So >>>All Parameters in Ball valve Design are Dependent on ball Diameter.<<< is not a universally supportable assertion.






Mike Halloran
Pembroke Pines, FL, USA

 

[valvit]

There is no standard to refer to when determining the bore to sphere ratio. I agree it is true that the rest of the valve design is performed after the bore/seat design is complete...and in that manner, it can be said that the rest of the design is dependent on the bore...but to Mike's point, they are not directly related because you could over design the rest of the valve if you choose to do so.

Also to Mike's point...if you oversize the sphere of a ball, you may no longer fit the end-to-end length of ASME B16.10.

Diameter will not remain the same for increasing pressure classes. The total valve design must study the seat sealing forces acting on the ball, and whether they are acting in single-block or double-block. The spherical OD of the ball, then, along with material selection, must resist those seat forces.

valvit

 

[gerhardl]

Thank you for the 'overall' picture of construction Mike! Star for you!