J. Spence

A parametric study of metal-to-metal full face taper-hub flanges

The paper presents the results of a parametric study, using finite element analysis, of the behaviour of full face metal-to-metal taper-hub flanges. The important stress values in the flange have been obtained for a range of flange thickness, taper-hub thickness and length, when the shell/flange component is subject to internal pressure. The influence of the pre-stress in the bolts is examined. The results obtained have been compared with the predictions from the appropriate sections of the ASME, BS and the new European Unfired Pressure Vessel Standard (Draft BS: prEN 13445).

A simple stress analysis for out-of-round, pressurised pipe bends

Abstract The importance of considering the effect of cross-sectional shape imperfections on the stress in pressurised tubes is well known. Nevertheless, little information is available to assist the designer other than for idealised bisymmetric (oval or elliptical) cross-sections. It is the intention of this paper to provide a simple stress analysis for a pressurised pipe bend, whose cross-section exhibits arbitrary small deviations from circularity, as a first step in resolving this deficiency. By way of example, a semi-oval/semi-round cross-section, often found in practice, is analysed and compared with more exact calculations.

The influence of flanged end constraints on smooth curved tubes under in-plane bending

Abstract A theoretical solution is presented for the in-plane bending linear elastic deformation behaviour of smooth circular cross-section, constant thickness pipe bends whose ends are terminated by rigid flanges. The technique employs the theorem of minimum total potential energy with suitable kinematically admissible displacements in the form of trigonometric series. Results are given covering a fairly wide spectrum of practical bend geometries. These are compared with previous theoretical predictions and with various published experimental data. Some test results which were obtained during the present investigation are also given.

Flexibility of smooth circular curved tubes with flanged end constraints

Abstract A theoretical solution is presented for the in-plane bending linear elastic deformation behaviour of smooth circular cross-section, constant thickness, pipe bends whose ends are restrained by rigid flange constraints. The analysis is based on an energy method and convergence features are examined and illustrated. Sufficient results are presented to cover virtually the complete range of practical geometric parameters, including various bend angles. The final converged results are given in a form which will be of direct use to designers and suitable for inclusion in future design codes. The theoretical results are compared with previously published test data and with some experimental results obtained during the present investigations.

The radial loading of cylindrical vessels—influence of attachment rigidity

Abstract The present version of the Pressure Vessel Standard, BS 5500 1 restricts the design of the local load type situations to certain vessel and attachment geometrics. This paper identifies the main underlying reasons for these restrictions; which are a limitation of the deflection and rotations by the use of small displacement analysis, and a neglect of the rigidity of the attachment. This paper addresses the influence of the attachment rigidity by considering a number of attachment thicknesses. The companion paper 2 considers the large displacement phenomenon and brings the two effects together in a design approach for these components. The method proposed provides a series of stress and displacement correction factors whereby the existing British Standard design method can be modified to cover the entire range of geometries up to ( C φ R ) = 0·25 for all values of ( R T ) up to 250.

Stress analysis of smooth curved tubes with flanged end constraints

A detailed experimental stress analysis programme is described on smooth pipe bends with flanged end constraints loaded under in-plane bending. A 335·6 mm (14 in) diameter steel pipe bend with special adjustable flange type constraints was extensively strain gauged and complete stress distributions were obtained for flanged bend angles of 90° and 180°. Two smaller 114·3 mm (412 in) diameter flanged steel bends of 90° and 180° but different curvature were also tested. A theoretical development for the stresses in bends bounded by rigid flanges is described and results given for a complete range of geometries. Detailed comparisons are made between the theory and experiments and the agreement is good.

A comparison of approximate methods for estimation of the creep relaxation of a curved pipe

Abstract The relaxation of stress in a linear, thin shell model of a curved pipe constrained to have a fixed rotation and expanding inelastically due to creep is represented by an equation of evolution in time. Using finite differences this continuous system is reduced to a finite set of initial value problems which are numerically integrated using a second order Runge-Kutta method. Thus the relaxation of the resultant in-plane bending moment can be deduced. Results are compared with two simple approximate methods with important repercussions on high temperature pipework design.

The radial loading of cylindrical vessels : influence of large displacements

Abstract This paper examines the behaviour of cylindrical vessels when local radial loads are uniformly applied in both the inward and outward direction. A parametric study is conducted to examine the effect of large displacements on the maximum stresses and displacements which occur in the vessel. Finally a design method is proposed which combines the results obtained for different attachment rigidities1 with the present study on the influence of large displacements. The method proposed provides a series of stress and displacement factors whereby the existing British Standard design method2 can be modified to cover the entire range of geometries up to ( C φ R ) = 0·25 for all values of ( R T ) up to 250.