End Preparation of ASME B16.9 BW Fittings

Butt welding pipe fittings manufactured in accordance with ASME B16.9 may be furnished with three types of welding ends depending on its nominal wall thickness, t:

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• When t is less than 5 mm [0.19″] for carbon steel or ferritic alloy steel and 3 mm [0.12″] for austenitic steel or nonferrous alloys, the fitting shall be furnished with cut square or slightly chamfered ends. It is often called “plain end”.

• When 5 mm [0.19″]≤ t ≤ 22 mm [0.88″] for carbon steel or ferritic alloy steel, or 3 mm [0.12″]≤ t ≤ 22 mm [0.88″] for austenitic steel or nonferrous alloys, plain bevel ends shall be furnished as shown in Illustration A.

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• When t is more than 22 mm [0.88″], compound bevel ends shall be furnished as shown in Illustration B.

Moreover, unless otherwise specified by the purchaser, transitions from the welding bevel to the outside surface of the fitting and from the root face to the inside surface of the fitting shall be lying within the maximum envelope, which is usually at the manufacturer’s option. Both A and A’ zones in Illustration A and B are known as the transition contours.

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*Click to view dimensions of various ASME B16.9 standard fittings.

We specified and ordered elbows with the following description:

90 DEG LR ELBOW, S-40S, BE, ASTM A-403 GR WP304L, SMLS, B16.9

The vendor fabricated the elbows by bending S-80S pipe and then counter-bored the ends to match the S-40S connecting pipe. The vendor than stamped the elbows as being S-40S.

The vendor is pointing to a sentence in B16.9 to justify what they did. It is:
In order to meet design or manufacturing requirements, it is expected that some portion of formed fittings may have to be thicker than the pipe wall with which the fitting is intended to be used.

Further, B16.9 states:
6.2.2 Bore Diameter. Bore diameters away from the ends are not specified. If special flow path requirements are needed, the bore dimensions shall be specified by the purchaser.

We believe we should not have to specify the S-40S bore as a 'special' requirement and that we are justified to believe that the elbows should have been supplied as S-40S.

The analysis for the pipelines may not be conservative based on the as-supplied fittings. They are heavier, stiffer, and do not have the same flow area.

So, is this a common vendor practice? What experience do others have regarding this issue?

thanks
Mark I believe, when taking a pipe of 40S and stretching to make it an elbow, the extrados will have less thickness, than 40S. So heavier thickness is required to work on.
Also as you mentioned ASME B16.9 alerts that the thickness can be heavier.
So in my opinion (if flow area reduction is not causing much of a problem), then you should accept this elbow.
In stress analysis, there will not be significant difference. If you doubt this, then do one thing, as you are in procurement phase, this means engineering is already done and you would have the stress model. Model these elbows with heavier thickness and then check the result.