Some aspects of unconfined gas and vapour cloud explosions

The experimental and theoretical work on the various phenomena normally considered under the heading of unconfined explosions has been critically assessed. Special attention has been paid to studies which may provide models of phenomena involved.     

Consequence analysis to determine damage to buildings from vapour cloud explosions using characteristic curves

The objective of this paper is to propose a methodology to estimate the consequences to buildings from the pressure wave caused by unconfined vapour cloud explosions (VCEs). This methodology is based on the use of characteristic overpressure-impulse-distance curves, shown in a previous paper [F. Diaz Alonso, E. Gonzalez Ferradas, J.F. Sanchez Perez, A. Mi?ana Aznar, J. Ruiz Gimeno, J. Martinez Alonso, Characteristic overpressure-impulse-distance curves for vapour cloud, explosions using the TNO Multi-Energy model, J. Hazard. Mater. A137 (2006) 734-741]. They allow the overpressure and impulse at each distance from the explosion to be determined. Since they can be combined with damage criteria (such as those shown by the PROBIT equations), they can be used to perform consequence analysis as the damage is shown in the same diagram as the overpressure, impulse and distance. Since damages suffered by buildings usually affect people inside, it is important to take them into account when performing consequence analysis. This is done in this paper, where diagrams and equations are presented to determine minor damage to buildings (broken windows, displacement of doors and window frames, tile displacement, etc.), major structural damage (cracks in walls, collapse of some walls) and collapse (the damage is so extensive that the building is partially or totally demolished). This paper completes the consequence analysis to humans outdoors shown by F.D. Alonso et al. [F. Diaz Alonso, E. Gonzalez Ferradas, T. Jimenez Sanchez, A. Mi?ana Aznar, J. Ruiz Gimeno, J. Martinez Alonso, Consequence analysis to determine the damage to humans from vapour cloud explosions using characteristic curves, J. Hazard. Mater., in press].     

Consequence analysis to determine the damage to humans from vapour cloud explosions using characteristic curves

The aim of this paper is to provide a methodology to facilitate consequence analysis for vapour cloud explosions (VCE). Firstly, the main PROBIT equations to evaluate direct damage on humans from those accidents (eardrum rupture, death due to skull fracture, death due to whole body impact and lung damage) are discussed and the most suitable ones are selected. Secondly, a new methodology is developed to relate characteristic overpressure-impulse-distance curves for VCE, obtained in a previous paper (F. Diaz Alonso et al., Characteristic overpressure-impulse-distance curves for vapour cloud explosions using the TNO Multi-Energy model, J. Hazard. Mater. A137 (2006) 734-741) with the selected PROBIT equations. This methodology allows the determination of damage as a function of distance to the accident's origin in only one step, using explosion energy and VCE Multi-Energy charge strength as input parameters.     

Characteristic overpressure-impulse-distance curves for vapour cloud explosions using the TNO Multi-Energy model

A number of models have been proposed to calculate overpressure and impulse from accidental industrial explosions. When the blast is produced by ignition of a vapour cloud, the TNO Multi-Energy model is widely used. From the curves given by this model, data are fitted to obtain equations showing the relationship between overpressure, impulse and distance. These equations, referred herein as characteristic curves, can be fitted by means of power equations, which depend on explosion energy and charge strength. Characteristic curves allow the determination of overpressure and impulse at each distance.     

Strain measurement with particular reference to cast iron

The general planning procedure for development testing at the author's firm is outlined. Strains in static tests of cast iron components under loads simulating service conditions are surveyed by brittle coatings and measured by strain gauges with incremental and shake-down load application. The fatigue life is then estimated in a novel manner by reference to the S/N curves established by Deere in push-pull tests on various cast irons. For nonzero mean strains, reference is also made to the static stress-strain curves for the tested material and to its Goodman diagram so that an equivalent strain reversal can be deduced and the Deere curve applied. For varying loads Miner's rule is invoked.     

Iterative methods based on domain decomposition,with particular reference to problems of machining distortion

We consider some iterative methods for problems of elasticity theory based on the idea of substructuring. Suppose that the given complicated domain can be decomposed into two or more simple subdomains for which solutions are available. In contrast to costumary methods of substructuring, we allow subdomains to overlap, or one to be inside another. The given domain can be formed in a rather flexible way as a union, product, or relative omplement (difference) of subdomains. We study several iterative schemes of patching solutions for subdomains, to give the solution of the required problem. Convergence is established by presenting the operator of an iterative procedure as a product of two or more projectors. We then apply one of the algorithms for a problem of machining distortion as a result of residual stresses.     

Artificial adjustment of element stiffness with a particular reference to plate bending

A finite element may satisfy all convergence requirements and work well except for being too stiff or too flexible when the mesh is coarse. Here we discuss a technique for softening or stiffening such elements, provided that they have internal degrees-of-freedom. The technique is applied to a previously derived plate element, and the element is found to be much improved.     

Processing of low grade tungsten ore concentrates by hydrometallurgical route with particular reference to India

Tungsten, because of its high strength and high melting point occupies a prime position amongst metals. With depletion of high grade resources considerable R and D work is still being carried out in tungsten producing countries around the world for the processing of low grade and secondary resources. The paper gives a brief review of the hydrometallurgical processes developed to recover tungsten from low grade concentrates. The R and D work carried out on purification and recovery of tungsten as tungstic oxide/ammonium paratungstate (APT) from a number of off-grade products such as table concentrate (WO₃=66%, SiO₂=2·2%, S=1·8%), middlings (18–20% WO₃, and 28–30% S) and jig concentrate (4·6% WO₃) are discussed in this paper. It has been found that more than 75% of silica and 90% of sulphur could be removed from the table concentrate by curing with hydrofluoric acid and subsequent roasting of the desilicated product at 650°C. In the case of middlings, it was possible to recover over 90% of tungsten as tungstic oxide by an oxidative roast followed by pressure leaching with soda. A detailed study on the low grade jig concentrate to recover tungsten as APT, showed that over 90% extraction was possible by adopting the pressure leaching-solvent extraction route. Effect of parameters such as soda concentration, time, temperature and pressure during leaching; as well as extraction and stripping behaviour of tungsten from leach solution at different pH and aqueous to organic ratio during solvent extraction with Alamine-336, were studied and a flow-sheet was developed for processing of jig concentrate analysing 4·6% WO₃.     

A comparison of mean and range charts with pre-control having particular reference to short-run production

This paper provides a rationale for making a statistical comparison between the techniques of ‘pre-control’ and traditional X and R charts. Special attention is drawn to the application of both techniques to the short run manufacturing environment where, for the use of X and R charts, parameter estimation is a problem. The total discussion is in the context of the manufacture of discrete items.     

The optimum design of fluid distribution networks with particular reference to low pressure gas distribution networks

This paper is concerned with the development of a computational algorithm to find the optimal solution to the fluid network distribution design problem. The problem is formulated as a non-linear mathematical optimization problem and is solved using a sequential unconstrained minimization technique. Illustrative examples are included and the design solutions obtained compared with the solutions obtained using a parametric method.     

A fire code for the New Zealand meat freezing industry with particular reference to cold stores

This paper describes building standards relating to the fire code and their application to cold stores.Emphasis is placed on a policy for a large industrial complex with single management capable of ensuring permanent fire safety measures, emergency procedures and intensive staff training. The management can thus co-ordinate all aspects of fire prevention and decide which buildings should incorporate fire safety measures and the extent to which these should be implemented. Emphasis is especially laid on staff safety, specifying minimum egress distances and easy fire fighting access. The use of sprinklers, located selectively, is advised in some parts of the building.The fire code represents a consensus view of design engineers, fire fighters, local government, insurance companies and meat company owners and operators.     

Curved finite elements and shell theories with particular reference to the buckling of a circular arch

The choice of strain-displacement relations to fomulate curved finite elements for the geometrically nonlinear analysis of deep thin shells of general shape is discussed. It is clearly demonstrated on a simple arch problem how the strain-displacement relations can affect the buckling pressure and it is concuded that inconsistent expressions should be avoided.     

Young's modulus for carbides of 3d elements (with particular reference to Fe3C)

Abstract

The Young's modulus of transition metal carbides has been calculated from their assessed thermal properties to explain why the modulus of steels and white cast irons can be only marginally altered by changes in composition or heat treatment. It is shown that the modulus of cementite (200 GN m^?2) is virtually identical to the value calculated for pure ferrite (215 GN m^?2). The predicted systematic variation for the modulus both with structure and position in the periodic table rationalises previous isolated experimental observations and confirms that the MC carbides of the group IV elements should have the most powerful strengthening effect in a matrix of their parent metal.

MST/1909