The wall thicknesses of  ball valves are pre calculated and are given for a specified rating in 16.34. It is like ANSI B 16.5 for flanges. But the difference in case of valves is that, the B 16.34 thickness are minimum required, you may exceed the thickness and yet you will be under the ambit of the ANSI B16.34. As regards it is common practice to adopt the thickness specified in B 16.34 even for the API 6D valves. The lead for this is in the clause 6 of API 6D. If you are valve manufacturer, then when you standadize your model of valves, you are expected to have analyzed the thickness required and maintain the records. If you are buyer or user of valves, you will never see the thickness of the valve in valve cross section drawing of the supplier/manufacturer under the guise that it is proprietory information. If you are specification engineer then you better specify that the minimum thickness shall meet ANSI B 16.34, there by you can assign your QC/Inspector to verify whether the thickness as per ANSI are met.

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