Stress intensification factors (SIFs) are published in the piping codes for tees; branch connections where the branch intersects the header pipe at 90 deg. These factors when multiplied by the nominal stress provide a measure of the increased local stresses at the junction of the two pipes. However, in cases where the branch pipe meets the header at an angle of other than 90 deg, the main piping codes do not provide a method of calculating the SIFs. This presents a difficulty for the pipe stress engineer who must determine appropriate SIFs, usually in a conservative way and then manually enter these into the pipe stress program. This paper summarizes some of the published methods of calculating SIFs for a limited range of lateral branch connections and makes recommendations based on comparisons with finite element analysis (FEA) studies. It also includes recommendations on how such FEA studies should be applied in order to provide suitable SIF values.

Issue Section:
Design and Analysis
Topics:
Finite element analysis, Pipes, Stress

References

1.
Wais
,
E.
, and
Rodabaugh
,
E. C.
,
2005
, “
Background of SIFs and Stress Indices for Moment Loadings of Piping Components
,” EPRI Technical Report 1012078.
2.
Wais
E.
, and
Rodabaugh
,
E. C.
,
1998
, “
Stress Intensification Factors and Flexibility Factors for Unreinforced Branch Connections
,” Technical Report 110996. Available at: http://www.epri.com/abstracts/Pages/ProductAbstract.aspx?ProductId=TR-110996
3.
Bhattacharya
,
A.
,
2011
, “
A Finite Element Based Study on Stress Intensification Factors (SIF) for Reinforced Fabricated Tees
,” NWC11_140, NAFEMS World, Congress Boston, MA.
4.
Rodabaugh
,
E. C.
,
1987
, “
Accuracy of Stress Intensification Factors for Branch Connections
,” WRC Bulletin 329, Welding Research Council, New York.
5.
Rodabaugh
,
E. C.
, 2009, “
Stress Intensification Factors, Stress Indices and Flexibility Factors
,”
Companion Guide to the ASME Boiler and Pressure Vessel Code
, 3rd ed., Vol. 2,
K. R.
Rao
, ed., ASME, NY, Chap. XXXVIII.
6.
ASME B31J
,
2008
, “
Standard Test Method for Determining Stress Intensification Factors (i-Factors) for Metallic Piping Components
,” The American Society of Mechanical Engineers, New York.
7.
ASME B31.1
,
2010
, “
Power Piping
,” The American Society of Mechanical Engineers, New York.
8.
ASME B31.3
,
2012
, “
Process Piping
,” The American Society of Mechanical Engineers, New York.
9.
ASME Boiler and Pressure Vessel Code, Section III, 2010, Nuclear Power Plant Components, American Society of Mechanical Engineers, New York.
10.
Vu
,
P.
,
2011
, “
Revision of B31 Code Equations for Stress Intensification Factors and Flexibility Factors for Intersections
,”
2011 ECTC Proceedings
, Fayetteville, AR.
11.
Creates
,
D. H.
, and
Côté
,
D. P.
,
2012
, “
Alignment of Stress Intensification and Flexibility Factors for The B31 Book Sections
,”
PVP2012-78047
,
Proceedings of the ASME 2012 Pressure Vessels & Piping Conference
, Toronto, Ontario, Canada.
12.
Xue
,
L.
,
Widera
,
G. E. O.
, and
Sang
,
Z.
,
2006
, “
Flexibility Factors for Branch Pipe Connections Subjected to In-Plane and Out-of-Plane Moments
,”
J. Pressure Vessel Technol.
,
128
, pp. 89–94.
13.
Suanno
,
R. L. M.
, and
Figueiredo
,
M. P.
,
2002
, “
Stress Intensification Factors for Tee or Branch Connections
,”
INAC 2002
, International Nuclear Atlantic Conference.
14.
Raju
,
P. P.
,
1985
, “
A Parametric Three-Dimensional Finite Element Study of 45 Degree Lateral Connections
,” WRC Bulletin 301, Welding Research Council, New York.
15.
Rodabaugh
,
E. C.
,
1991
, “
Stress Indices, Pressure Design And Stress Intensification Factors For Laterals in Piping
,” WRC Bulletin 360, Welding Research Council, New York, NY.
16.
“Piping Auxilliaries—Piping Stress Analysis,” Course C1/6/32, Twikenham College of Technology, Middlesex, UK, p.
40
.
17.
Basavaraju
,
C.
, and
Sun
,
W. S.
,
2004
,
Stress Analysis of Piping Systems
,
Piping Handbook
,
McGraw Hill, NewYork
, Chap. IV.
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