Calculating of Valid SIF for D/t>100 Condition (B31.3)

[khadiv]

Hi
Facing D/T>100, Code doesn't suggest any SIF.So how can we acquire valid SIFs? For Reinforced and Unreinforced branches(Stub-in), I've calculated Inplane and Outplane SIFs by Nozzle Pro Software.
1. The Inplane and Outplane SIF (calculated for Reinforced branches) are not the same like CII. Is it correct?
2. How are valid SIFs for an elbow calculated?
3. How are valid SIFs for a Welding Tee obtained?

Thanks

 

[richay]

The SIF equations found in the piping codes are based on tests (by Markle) performed in the 1950's on 4x4 STD fittings. This is why the D/t warning/limit is in the Code.

Once you step outside of the limits addressed by the Code(s), you're on your own. In this particular instance you have (in my opinion) only two choices (a) ask your vendor to test the fittings and give you the SIFs, or (b) perform a Finite Element analysis and determine the SIFs analitically.

If you decide to go with method (b), check out FE/Pipe by Paulin Research, or e-mail tony@paulin.com

Richard Ay
COADE, Inc.

 

[LSThill]

Large Diameter Ratio Shell Intersections

WRC Bulletin 497

Large Diameter Ratio Shell Intersections
Part 1: Design of Large Diameter Shell Intersections Subject to Pressure and External Loadings
Part 2: Parametric Finite Element Analysis of Large Diameter Shell Intersections (Internal Pressure)
Part 3: Parametric Finite Element Analysis of Large Diameter Shell Intersections (External Loadings)

Cylindrical shell intersections are structural configurations commonly used in many industries, such as pipeline transportation, nuclear and power engineering, chemical and petrochemical engineering, aerospace, etc. Under internal pressure or external loadings, high local stresses occur at the Shell intersection region due to the geometric discontinuity. Therefore, the study of the influence of the geometric parameters for a specific design configuration on the maximum stresses at shell intersections due to various loadings thus has great practical value.

In the past thirty years, considerable effort has been expended by stress analysts and designers all over the world in attempts to achieve a reasonable design procedure for shell intersections. WRC Bulletin 107 [1], which is based on Prof. P.P. Bijlaard's work, and WRC Bulletin 297 [2], which is based on Prof. Steele's work, provide guidance for the evaluation of shell and nozzle stresses due to external loadings. However, for large diameter ratio (0.5
A comprehensive parametric study of large diameter ratio cylindrical shell intersections subjected to internal pressure and external loadings was conducted on behalf of the Pressure Vessel Research Council. The configuration employed in this parametric study is idealized and consists of two thin shell cylinders intersecting normally with no transitions, reinforcements, or fillets in the junction region. This parametric study was divided into two phases. Phase I is for internal pressure while phase II is for external loadings. The external loadings considered are in-plane moment on the nozzle, out-of-plane moment on the nozzle, and axial force on the nozzle.