Mismatch bores/ Wall thickness - Welding (EN and ASME) 1

[pch1]

On a project, for economic reasons, we have pipe which has a thinner wall thickness than standard off the shelf fittings.

Before anyone says to match the wall thicknesses (in an ideal world) you may want to consider the vast range of pipe wall thicknesses available in the EN standards.

Could anyone tell me where I could find the maximum permissable difference in wall thicknesses allowable for welding, I'm aware we may need to grind away some of the material of the fittings.

I have access to most EN standards but only a few ASME standards.

Regards
Paul Hearn

 

[eyec]

assuming the IDs are the same -
while adhering to the applicable Code press/temp calcs for the thinner wall pipe, a tapered weld prep on the thicker fitting should get you there.





Steven C
Senior Member
ThirdPartyInspections.com

 

[BigInch]

Since ODs are usually the same, its not likely that the ID are.

3/16 inch is a typical limit of mismatch wall thicknesses. No standard I know of covers this, but I don't know all of them yet.

http://virtualpipeline.spaces.msn.com

"What gets us into trouble is not what we don't know, its what we know for sure" - Mark Twain

 

[eyec]

ok, for economic reasons - fit in a piece of pipe that adheres to biginch's reccommendation for both ends - pipe and fitting.

Steven C
Senior Member
ThirdPartyInspections.com

 

[pch1]

BigInch
3/16 is approximately 4.7 mm - can you recall where you got that figure from?
I can find an EN standard that indicates the mismatch of a circumference and alignment but doesn't mention anything about mismatch of wall thicknesses.

 

[vzeos]

pch1.
Take a look at ASME B31.8, Appendix I

 

[pch1]

Thanks very much Vzeos.

 

[Berndt]

Having only recently read this I thought back to this thread:
ASME B16.9 requires taper boring for any misalignment between fitting and pipe greater than 1.5mm. Although it seems that this is limited to fitting proof testing rigs.