9,606 research outputs found

    A parametric study of alternative support systems for cylindrical GRP storage vessels

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    Paper presenting a parametric study of alternative support systems for cylindrical GRP storage vessels

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

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    A flexible sling support arrangement for horizontal glass reinforced plastic pressure vessels is examined using advanced finite element methods. A mathematical model is produced employing a suitable analysis capable of representing the non-linear behaviour of a sling supported GRP vessel. This system is used to examine the phenomena occurring at the interface between the vessel and the supporting belt. Each component is initially considered some distance apart and then brought together using three-dimensional contact surfaces. External loads are thereafter applied to the combined model. Although several numerical difficulties arise due to the difference in flexibility between the vessel shell and the sling support, these are overcome and the resulting vessel strains and contact interface pressures show good agreement with experimental work. The magnitudes of the strains at the location of the saddle horn are significantly reduced. Results of a parameter study are also presented which show the effect of the sling position together with the influence of the wrap-round angle and a number of recommendations are made with respect to design

    Horizontal saddle-supported storage vessels: Theoretical and experimental comparisons of plastic collapse loads

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    Previous experimental work (1) on cylindrical vessels supported at the ends and subjected to central loading indicated that different collapse mechanisms could occur when the loading is applied either through loosely fitted saddles or through welded saddles. The modes of failure are dependent upon the value of the R/t ratio of the vessel. In general, progressive plastic collapse occurs in vessels with low values of R/t ratio, typically less than 200, and elastic-plastic buckling is observed in vessels with higher R/t ratios. The aim of this paper is to examine various theoretical analyses for plastic collapse loads, applicable to vessels with low values of R/t ratio, and compare these with the experimental results obtained by the authors and others. The theoretical behaviour appropriate for the thinner vessels, where the mode is failure is by buckling, has been previously examined by the authors elsewhere (2) although all the experimental values are included here for completeness. A number of classical and numerical analytical methods are employed to obtain the plastic collapse loads. Comparisons with the experimental results show that the elastic-plastic finite element analysis gives the best agreement. Further work in the form of a parametric study has been conducted on a range of vessels to enable a design method to be established. This is published as a companion paper in this volume

    Horizontal saddle-supported storage vessels: A parametric study of plastic collapse loads

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    Previous work by the present authors compared various theoretical methods with simple experiments for the plastic collapse load on end supported vessels loaded centrally by rigid saddles. It was found that the best agreement was obtained by using an elastic-plastic finite element analysis approach. In the present paper the elastic-plastic method has been used to examine the effect of various geometric parameters on the collapse load. A symmetrical model which replicated the geometric features of the experiments can be used to give an indication of the effect of specific isolated geometric variables but for others and for the purposes of undertaking a full parametric survey the model was modified to reflect an actual twin saddle supported vessel

    UK Rules For Unfired Pressure Vessels

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    The present code PD 5500, formerly BS 5500 [1] evolved partly from the well-known BS 1500 [2] in the 1950's and BS 1515 [3] first published in 1965; the latter permitted higher level allowable stresses and more advanced rules. In 1969, following a report from the Committee of Enquiry into the Pressure Vessel Industry, the British Standards Institution brought all the pressure vessel interests together under one general committee in order to rationalise the activity. This became PVE/ and presides over a large committee structure. There are a series of functional sub-committees who deal with specific aspects and a large number of technical committees as well as many additional sub committees and working groups. Most of these meet regularly. The technical committee PVE/1, Pressure Vessels, has overall responsibility for BS 5500. The functional committee PVE/1/15 Design Methods has an overall responsibility relating to 'Design' with particular reference to the design section of BS 5500 (Section 3). The first edition of BS 5500 was issued in 1976. The actual issue was delayed for some time because, in the early 1970's, there was an attempt in Europe to produce an international pressure vessel standard. A draft of the international standard appeared as ISO DIS 2694 [4] in 1973 but it was not generally accepted and the attempt was abandoned in the mid 70's. It was decided to use some of the material from 2694 within BS 5500 so that although the Standard was long delayed it benefited to some extent from the international efforts. Initially, committee PVE/l set out the concept of a "master" pressure vessel standard which could readily be applied to any vessel in either ferrous or non-ferrous materials and for highly specialised application with the minimum of supplementary requirements. The layout of BS 5500 is consistent with this concept and although the Standard has perhaps not fulfilled this high ideal, it has certainly been employed widely in many industries including non pressure vessel type applications. When issued it had a number of distinctive features compared with other pressure codes viz; weld joint factors were removed, the present three categories of construction were introduced, there was a new novel external pressure section, it has a loose leaf format and an annual updating was introduced. Further editions of BS 5500 have been issued every three years since 1982

    On the plastic collapse of horizontal saddle supported storage vessels

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    The present paper summarises a comprehensive programme of work on collapse loads of horizontal cylindrical saddle supported storage vessels. A programme of tests was conducted on 40 model vessels that included both welded and loose saddles. Different collapse behaviours were observed depending largely on the radius to thickness ratio of the vessels. A range of theoretical approaches were explored and compared with the experimental results. The best theoretical comparison was then used to conduct a parametric survey covering a total of 218 cases. The results of the survey have been presented in the form of simple design graphs

    Parametric plastic collapse loads and their validation for horizontal saddle supported storage vessels

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    In general, progressive plastic collapse occurs in vessels with low values of R/t ratio, typically less than 200, and elastic-plastic buckling is observed in vessels with higher R/t ratios. The aim of this paper is to examine various theoretical analyses for plastic collapse loads, applicable to vessels with low values of R/t ratio, and compare these with the experimental results obtained by the authors and others

    The buckling and collapse behaviour of saddle-supported cylinders - Keynote Lecture

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    Recent work by the present authors on the collapse conditions for horizontal cylindrical saddle supported storage vessels is described and reviewed. Attention is directed to a range of geometries, typically R/t < 200, where plastic collapse type failure may be relevant. A series of forty tests on end-supported model cylinders loaded centrally by a rigid saddle were performed and a variety of theoretical methods were used for comparison with the test results. It was found that the best agreement was obtained by using an elasticplastic finite element analysis approach. The results of a parametric survey based on the elastic-plastic finite element method are summarised. The paper reports some validation checks, which have been performed to support the parametric results

    Threshold of microvascular occlusion: injury size defines the thrombosis scenario

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    Damage to the blood vessel triggers formation of a hemostatic plug, which is meant to prevent bleeding, yet the same phenomenon may result in a total blockade of a blood vessel by a thrombus, causing severe medical conditions. Here, we show that the physical interplay between platelet adhesion and hemodynamics in a microchannel manifests in a critical threshold behavior of a growing thrombus. Depending on the size of injury, two distinct dynamic pathways of thrombosis were found: the formation of a nonocclusive plug, if injury length does not exceed the critical value, and the total occlusion of the vessel by the thrombus otherwise. We develop a mathematical model that demonstrates that switching between these regimes occurs as a result of a saddle-node bifurcation. Our study reveals the mechanism of self-regulation of thrombosis in blood microvessels and explains experimentally observed distinctions between thrombi of different physical etiology. This also can be useful for the design of platelet-aggregation-inspired engineering solutions.Comment: 7 pages, 5 figures + Supplementary informatio

    Design and analysis of cold box and its internal component layout for kW class Helium Refrigerator/Liquefier

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    The indigenous HRL will have option for upgrading its cooling capacity upto ~2 kW at ~4.5 K. The cold box containing all cold equipment is designed considering strength and thermal aspects. Component layout inside the chamber is decided to maintain a temperature gradient through the length of the chamber. So, the chamber can be thought of two chambers; one 4 K part and another 20 K part. Stiffening rings, covers, gasket and saddle supports are designed. Strength analysis of the cold box is done in ANSYS. Piping and flexibility analysis is done in CAEPIPE. Support structures for all components are designed for permissible heat conduction as per HRL requirement. Entire cold box with its components is modeled in CATIA
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