What is meant by the term "misalignment" in a buttweld joint?

[KernOily]

So this is question #3 in my series of "Pipeline Fundamentals"... ;-)

In Sec. 406.2.2 of B31.4, it says "Deflections caused by misalignment up to 3 deg. are not considered miter bends." What do they mean by "misalignment"?

Thanks!!! Thanks!
Pete

 

[prex]

This should be the angle found at erection in a field weld between two pieces of piping that were designed to be perfectly aligned. prex
motori@xcalcsREMOVE.com

http://www.xcalcs.com

Online tools for structural design

 

[JerryD]

Misalignment in buttweld piping is where the Internal Diameters do not match up when pipe is being fabricated.

 

[KernOily]

Jerry - I thought the term for that was "high-low", or ovality?

Why would a degree specification be given if misalignment applied to the diameters? Thanks!
Pete

 

[apiguy]

Pete,

You are correct in your assumption. "Hi-Lo" is the non-standard term while "internal misalignment" is the preferred standard term. The CWI exam contains a few questions regarding the use of standard and non-standard terms. Some others are "Fish-eye", "suck-back" and the like. Basically... just good old-fashioned welding slang. Richard Schram
Mechanical Integrity Specialist
Pharmacia Global Supply Arecibo-P. Rico
rschram@pharmacia.com

 

[Flareman]

Re your post,
as the comparison is to Miter bends, it seems that the code clearly means an axial misalignment which would simulate a small accidental Miter created during construction.
Was it a test ?
I hope I'm correct other-wise I'll go stand in the corner for an hour.

 

[Placy]

Misalignment or mismatch is when pipe/pipe, pipe/fitting or fitting/fitting are not aligned corectly thus causing the internal diameters to be stepped. This can be aliviated by using either an external or internal pipe clamp and checking with a hi-Low gauge.General exceptance in the petro/chem industry is 1mm mismatch is acceptable.

 

[owlscreech]

A mitre pipe joint is where the flow axes of the two pipes intersect at an angle. The <= 3 degrees specified is a way to say that this situation does not exist.