Flange Leakage/Stress Calculations - CAESAR II - Help

CAESAR II Users Guide

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English
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CAESAR II
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CAESAR II Version
12

Main window ribbon: Analysis > Components/Equipment > ASME/ANSI Flanges

Performs ASME and ANSI flange stress and leakage calculations. The stress calculation methods are from the following sources:

  • ASME Section VIII

  • ANSI B16.5 Rating Tables

The leakage calculations are also based on the B16.5 rating table approach. Leakage is a function of the relative stiffnesses of the flange, gasket and bolting. Using the B16.5 estimated stress calculations to predict leakage does not consider the gasket type, stiffness of the flange, or the stiffness of the bolting. Using B16.5 to estimate leakage makes the tendency to leak proportional to the allowable stress in the flange. A flange with a higher allowable is able to resist higher moments without leakage. Leakage is very weakly tied to allowable stress, if at all.

Equations model the flexibility of the annular flange plate and its ability to rotate under moment, axial force, and pressure. The results compare favorably with three-dimensional finite element analysis of the flange junction. These correlations assume that the distance between the inside diameter of the flange and the center of the effective gasket loading diameter is smaller than the distance between the effective gasket loading diameter and the bolt circle diameter. In other words, that (G-ID) < (BC-G), where, G is the effective gasket loading diameter, ID is the inside diameter of the flange, and BC is the diameter of the bolt circle.

The following trends apply:

  • Thinner flanges have a greater the tendency to leak.

  • Larger diameter flanges have a greater tendency to leak.

  • Stiffer gaskets have a greater tendency to leak.

  • Leakage is a function of bolt tightening stress.

To begin working with the flange stress and leakage calculations, specify a new job name in the New Job Name Specification dialog box or click Browse to navigate to an existing job file.

All CAESAR II analyses require a job name for identification purposes. After you create or open a job, you can enter input data and then define, analyze, and review your data.

The software opens the Flange Leakage/Stress Calculations dialog box.

Input for the flange stress and leakage calculations is divided into four input tabs: