16

To:
Subject: Weld necks on 6BX flanges

Question:

Can I  order  an  API, 4-1/16 10K x 4" XXH weldneck flange having the weld neck end 4-1/2” O.D. and the bore the same as 4" XXH pipe? Does the flange meet API Spec. 6A if forged from 4130, 75K material? I understand that you can order any API 10,000 psi flange with an optional weld neck and bore, as long as it's made from certain materials and you have a qualified welding procedure to join the flange and pipe material.

I have someone asking me if it’s OK to weld a flange with these dimensions to 4” XXH pipe, when they see the published “Standard Dimensions” of a 4-1/16” 10K flange weld neck O.D. and I.D. does not match 4" XXH pipe.

Answer:

Operators often order 4-1/16" 10K ( 10M ) flanges with non-standard weld necks, sized to match standard pipe sizes. Operators  ordering such flanges realize that their flange’s working pressure will not exceed that of the matching pipe they have selected. These flanges usually cannot bear the API Monogram.

No matter what you do, the working pressure of any system equals the working pressure of its lowest pressure component. If the pipe won't stand the pressure, any attached flange and welding procedure used to attach it will not increase the strength of the pipe. Note also that 75K material exceeds that required for 10,000 psi. working pressure flanges, so unless you have data on the mechanical properties of the particular flange you have, you cannot count on the material exceeding 60K.

When you vary from dimensions and material requirements specified by recognized standards, e.g. API Spec 6A, then you should seek competent engineering advice.

Click here for a caution about 6BX weld neck flanges.

For more information about weld neck flanges click here.

Information above, and in other parts of this Web Site, may help persons who really seek to know. If you have a question, and you think WOODCO USA may have the capacity to answer it, please use our Contact Us link and give us a chance to help.

WOODCO USA provides Web Site Tools for identification, estimating, and reference only. Do not use this information for manufacturing or inspection. Users of these tools should not use them as a substitute for professional engineering advice.  Anyone making use of the information presented does so at his own risk and assumes any and all liability resulting from such use.