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Tips October - December 2006

Integrally Reinforced Branch Connection-1

Question: What is your recommended method of modeling an integrally reinforced branch connection? Do you include in the model the weldolet as a rigid element? Do you take the branch line to the centerline of the run line and place the SIF there?


Reply: Our recommended modeling procedure for integrally reinforced branch connection [i.e., Branch welded-on fitting (integrally reinforced) as given in Table D300 of Appendix D of B31.3 code] is as follows.


A) For d/D < 0.5:


For the branch (coming from end away from branch connection):
a) Model the piping up to piping-to-weldolet junction as "pipe" element.
b) Model the weldolet (from piping-to-weldolet junction up to the outer
surface of the header line) as another "pipe" element with equivalent thicker section properties.
c) Model a "rigid, massless link" between the branch node at the outer
surface of the header and the node at the intersection of the centerlines of the branch and header.
d) Specify SIF at the branch node where the weldolet "pipe" element ends
and the "rigid, massless link" begins.


For the header:
e) Model the two sides of the header (from the centerline intersection
point) as "pipe" elements.


B) For d/D > 0.5 (to be continued next month)

Integrally Reinforced Branch Connection-2

Question: What is your recommended method of modeling an integrally reinforced branch connection? Do you include in the model the weldolet as a rigid element? Do you take the branch line to the centerline of the run line and place the SIF there?


Reply: Our recommended modeling procedure for integrally reinforced branch connection [i.e., Branch welded-on fitting (integrally reinforced) as given in Table D300 of Appendix D of B31.3 code] is as follows.


Continuing from the previous month's tip:


A) For d/D > 0.5:


For the branch (coming from end away from branch connection):
a) Model the piping up to piping-to-weldolet junction as "pipe" element (same as for d/D < 0.5).
b) Model the weldolet (from piping-to-weldolet junction up to the node
at the intersection of branch and header centerlines) as another "pipe" element
with equivalent thicker section properties.
c) Specify SIF at the centerline intersection node.


For the header:
d) Model the two sides of the header (from the centerline intersection
point) as "pipe" elements (same as for d/D < 0.5).


Mr. Ron Haupt, who is a member of numerous piping related ASME, ANSI and other code committees, opines that the SIF formula given for Branch welded-on fitting (integrally reinforced) in B31.1 and B31.3 may not be appropriate for all cases: this is because 'h' given as equal to (3*3tn/r) [in B31.1] may not be applicable for some special cases. You need to decide whether this applies to your situation or not.