Seat Sealing Force - Ball Valve 1

[Sid89]

Does anyone know the calculations for determining the value of the downstream seat sealing force against the ball when there is no differential pressure in a floating balll valve?

 

[SPDL310]

The theoretically none. Depending on the design of the valve there will be some minor compression from tight part tolerances or if used seat springs.

 

[bcd]

With no differential pressure, upstream and downstream sealing force on floating ball is the same.

Definitely cannot be zero force. Floating ball seats need to support the weight of the ball at a minimum. Then extra compression is added to account for any plastic deformation of the seats, manufacturing dimensional tolerances, and ensure low-pressure sealing capability.

FEA can be used to get a close prediction of the seat force when valve is first assembled. But you should verify your computer models and material properties with tests.

 

[Sid89]

@bcd(Mechanical) ... is there any sample FEA calculations/modeling you have or refer me to, so I can have an idea what boundary conditions to apply, etc.

 

[bcd]

No. Don't have anything I can send you. Pretty straight forward non-linear FEA. Often can be done using 2D axisymmetric analysis so the model size is small and resolves quickly.

 

[LittleInch]

too many variable I think including the axial force especially if this is an end access two piece valve, or even as an insert with the two seats and the ball. lots of variation of design as well.

Why do you want to know?

You can only assume that in very low / no differential pressure the ball does not fully seat and can allow leakage, especially if the seats have been worn down a bit.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.