Seat calculations for floater ball valve 1

[Mous1747]

Hello Everyone,

I am trying to develop a calc sheet for the Teflon seat used on a floater ball valve but i am not sure what type of calculation it would be? is it just stress calculations based on the applied forces? is it wear calculation. or to calculate the amount of deflection maybe?

I hope someone can shed some light on this. any insights will be greatly appreciated.

 

[yousif aldossary]

good day dear
i have seen some ball valve catalogs and they alway mention that they design them accordance to API6D and ANSI 16.34 ( mainly for flanges) .

regards

 

[Mous1747]

Hi Yousif. the calculations for the body, adapter, ends, neck, bonnet are all per ASME 16.34 the flange is normally designed per ASME VIII. however there's no code for the seat design.

 

[gerhardl]

A (floating ball) valve will also have norms for exact described tests to verify that the construction and fabrication is OK. Examples are pressure tests, test for leakage, fire tests, SIL tests (verification of performance over time) etc.

One of the reasons is that all elements and details will vary and cannot be reasonably well described for exact technical calculation, but will have to be part of the overall general consideration of 'best practical solution'.

Teflon is a trade-name, not a material description, and will have different material properties, slightly varying from producer to producer and exact production recipe, mechanical form. metal backing and support etc. difficult to exactly normalize and standardize.

You will always come to an end point in standard description for a product where tests will have to be used to prove quality, in stead or on top of calculations.

Hope this will help you!

 

[bcd]

You are correct that there is no code for floating ball valve seat design. Dimensions for most of the valve are dictated by codes and standards. The seat design is the one critical part that is left to the engineering skills of the manufacturer. All the calculations you mention apply. Material stress, deflection, and wear. In addition, creep (cold flow) of the polymer material also needs to be considered. Calculations and FEA will only get you close. Ultimately you will need to verify the seat design works under all the rated conditions of the valve through testing.

 

[Mous1747]

Yes I agree to all the above but would it be the responsibility of the seat manufacturer to provide some or all of these design parameters and the associated calculations? they mostly depend on the material mechanical or physical properties

 

[gerhardl]

On last post above:
In my opinion only if this is a part of a specific valve order. The manufacturer can then select to bid or not. There is a border between what is required by regulation and tests on one side, and fabrication secrets on the other side.

 

[bcd]

Why would you think a manufacturer must provide or give away their design parameters? The manufacturer invested their money to develop the know-how, so it is their proprietary information. Options are to try and copy and hope you get it correct, hire one of their experienced engineers to teach you, or develop it on your own.

 

[Mous1747]

issue resolved and lesson learned

i just increased the height of the seat and increased the (pre-compression/squeeze/crush ) from .45 mm per seat to 1.45 mm

 

[SRIVINAYAK]

Mous1747
Hello..!! May I know what's the Floating Ball Valve size, class, bore, 1p, 2p, 3p!??

 

[Mous1747]

this was 8" 150# fanged end standard bore
i have done the same on 8" #300 and 6" #300