Pipe Bend Analysis For Shape Irregularities In Boiler Application

Determination of allowable pressure, which is one of the important criteria to evaluate the acceptability of pipe bends with shape irregularities, is complex as the analytical solution of the problem involves solution of complex differential equations. Finite element analysis is used in this paper to determine the allowable pressure ratio for pipe bends with varied range of ovality and thinning/thickening and external pressure. A set of pipe bends with shape irregularities obtained from ANSYS analysis is used to obtain a mathematical relationship between various design parameters of pipe bends namely pipe diameter, wall thickness, bend radius, ovality, thinning/thickening and the internal/external pressure load. The possible flexibility that can be introduced in the selection of ovality and thinning limits of pipe bends to reduce rejection has been suggested. A general mathematical expression relating internal pressure, shape imperfections and bend geometry is also presented. The analysis is carried over with structural ANSYS software.