WALL THICKNESS FOR BALL VALVES

[ALEXANDRAHARPER]

HI,

HOW CAN I KNOW THE WALL THICKNESS OF A BALL VALVE. i KNOW THAT MAYBE I NEED TO USE ASME B16.34, BUT I DON'T KNOW IF I NEED TO USE ANTHER SPEC. IF THE VALVE IS DESIGNED PER API 6D. PLASE HELP

 

[bmoorthy]

You are right the wall thicknesses of 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.

 

[bmoorthy]

In cse of API 600 valves the thickness required are higher than that of ANSI 16.34.

But for all practial purposes ANSI B 16.34 will do.

If your valves are of special design then the valve manufacturer will take up FEA or classical analysis as per ASME Sec VIII Div 1.

In fact ANSI B 16.34 briefly mentions reference to ASME Sec VIII Div 1.

But i have come accross valves that were designed to ASME Sec VIII Div 2. But our specification engineer and the user both were totally at loss as to how to handle the NDe associated with such valves.

One has to be cautious when multiple reference standards exists, you have to set your boundary conditions first.

Good Luck