Branch connections that are not in center of header pipe? Allowed per B31.3?

[frizzmizz]

Hello everyone,
just wondering if anyone has come across a situation where they needed to install a branch pipe on a header in a way that the center lines of the branch pipe does not intersect with the center line of header? I have attached a drawing which shows this case.

http://files.engineering.com/getfil...0-b5d2-4690-8ad4-cf5482a2224a&file=branch.JPG

I was reading B31.3 and seems like this is not recommended:
304.3.1(b) The rules in paras. 304.3.2 through 304.3.4 are minimum
requirements, valid only for branch connections in which (using the nomenclature of Fig. 304.3.3)
(1) the run pipe diameter-to-thickness ratio (Dh/Th)is less than 100 and the branch-to-run diameter ratio (Db/Dh) is not greater than 1.0
(2) for run pipe with Dh/Th ≥ 100, the branch diameter, Db, is less than one-half the run diameter, Dh
(3) angle  is at least 45 deg
(4) the axis of the branch intersects the axis of the run
(c) Where the provisions of (a) and (b) above are not met, pressure design shall be qualified as required by para. 304.7.2.

Can anyone confirm what should be done in this case? If we go ahead with this design should there be any additional analysis?
Would it be better to get designer to change this so the center lines intersect (no matter cost in field)?

Will appreciate any help. Thanks!

-FM

 

[TGS4]

This type of arrangement is done all of the time - even up to the limit of a tangential connection. The simplified calculations provided in B31.3 are not directly applicable - however most designers just provide reinforcement based on the major axis of the opening ellipse (as if it were a diameter).

 

[frizzmizz]

Thanks, that would make sense. Have you ever done any of the steps listed in para 304.7.2 for doing this?

 

[TGS4]

304.7.2(d) is my bread and butter.