Pipe Class change for a flanged valve 1

[pipe15]

The question has come up as to whether both flanges of a thru-bolted butterfly valve that also has a class change from B31.1 to ASME Section III should be ordered as ASME SA material or if the B31.1 side flange can be ordered as ASTM A material. I have attached a pic of the valve from the P&ID.

Would the answer change if the valve was not thru-bolted and each flange was secured with its own bolt set?

Part of the issue seems to be the hydrotest requirement differences between B31.1 and Section III.

thanks
Mark

 

[BigInch]

Change class at the up or downstream weld neck to pipe joint, not at the face of a flange.

"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek

 

[pipe15]

Thanks BigInch, but, are you saying that both flanges and the bolting should be specified as safety related material for this thru-bolted application?

and, what about non thru-bolted, would one side have ASTM material flange and bolting and the other have ASME material for the flange and bolting?

 

[BigInch]

I would normally order a valve (both sides) for the most severe condition, then make the class break off the valve and to the weaker side.

"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek

 

[BigInch]

That way it doesn't matter in which direction the valve might be installed.
If safety related, I would want the entire valve in compliance.

"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek

 

[Krausen]

Class changes should never occur between flange sets, even if it is possible to align the mating flange bolt holes. Always change classes at welds (e.g. at a flange weld neck to pipe weld). This usually isn't clearly shown on P&IDs, but should be on your physical piping dwgs.