Blast assessment of steel switch boxes under detonation loading scenarios

Abstract

A number of major industry incidents have occurred globally in recent years involving the ignition of a vapour cloud which resulted in loss of life and considerable damage. One such case was the Buncefield incident which occurred in 2005 and involved an explosion of two hundred and forty thousand cubic meters of vapour cloud which resulted in considerable damage to business and residential properties in the surrounding area. A number of overpressure indicators such as steel switch boxes were located at various points around this site. These were found deformed to different levels after the explosion. These overpressure sensitive objects were used to assess the overpressure level at the locations of the objects during the incident. This study describes full scale validation tests and numerical simulations of far-field air blast loading acting on deformable steel boxes in order to investigate possible forensic methods to aid the incident investigation. Subsequently, a number of numerical models with varying complexity are developed in order to simulate the tests. These consist of Lagrangian, uncoupled Eulerian–Lagrangian and coupled Eulerian–Lagrangian models. The models are validated against the test results from a gas detonation explosion. Comparison between the numerical and experimental results suggests that the coupled Eulerian–Lagrangian approach is able to accurately predict the deformation of the box under blast loading, but requires a prohibitive computational resource. On the other hand, the Lagrangian model tends to over-predict the results but with significantly lower computational cost. The present work shows that advanced finite element methods can be used for problems involving air blast loading and reliable results can be obtained. The validated finite element models of steel switch boxes could be a useful tool for forensic studies in explosion incidents to estimate the overpressure levels at the site.