The Twin-Saddle Support of Horizontal Multi-Layered GRP Vessels—Theoretical Analysis, Experimental Work and a Design Approach

Abstract

The maximum stress in a storage vessel generally occurs in the region of the support. In the case of lwin-saddle-supported horizontal vessels used for liquid storage under modest operational pressure, the strain on the inside suflace of the vessel, at the top of the support, is tensile. This can create problems in glass-reinforced plastic (GRP) composite vessels since local cracking of the inner surface may allow liquid ingress to the glass through the matrix with consequent premature local failure. This paper extends the earlier work done at the University of Strathclyde, Glasgow, on metallic vessels (assumed isotropic) and outlines a thin-shell analysis, appropriate for the layered GRP vessel, to derive the strain levels in the support region. Over several years experimental work has been carried out on a range of GRP vessels of various sizes. Of particular note three full-size GRP vessels have been extensively strain gauged and hydraulically tested to provide experimental results to validate the theoretical analysis. Using this analysis, a parametric survey has been conducted and a design approach presented, to enable the maximum strain to be determined for the symmetric laminated horizontal vessel.

The design of twin-saddle supported multi-layered glass-reinforced plastic vessels—the development of a parametric equation for the maximum strain

“…The maximum strain in these vessels is the circumferential strain in the critical horn region, the uppermost point of the support [8]. Using the PD 5500 approach a value for this can be obtained from the stress resultants, given in equation (3), using the simplified constitutive equations given in BS 4994 [2].…”

“…The same glass content was used in each lay-up; only the disposition about the wall centre-line of the CSM and the FW changes in the lay-ups given in Table 2. The analytical work by Tooth et al [8] was based on a Fourier series fit of the applied loads and a derivation of the interface pressures to satisfy equilibrium and compatibility of the saddle surface. In this it was found that the maximum strain in the vessel was at the 'horn' of the saddle (the uppermost point of the support), on the outside surface and in the circumferential direction.…”

“…In this the saddle interface can range from the 'rigid' to the flexible. The details of this analysis have been given by Tooth et al [8].…”

“…This can create problems in composite vessels since local cracking of the inner surface may allow liquid ingress to the glass through the matrix, with premature local failure by stress corrosion cracking. The analysis of this support problem has been solved using a double Fourier series by Tooth et al, [8], by which the maximum strain in the support region can be derived. The present paper presents a parametric study for an extensive range of vessels, in use in the process and chemical industries, using this analysis.…”

Numerical analysis of a sling support arrangement for GRP composite pressure vessels

“…Work by Tooth et al 7,8,9,10 employs a shell analysis and Fourier series approach that evaluates the form of the contact interface pressure profile. This is undertaken by subdividing the contact region into a number of discrete areas around the circumference and across the saddle width.…”