Research Team: Dr Luke A Louca, Professor Ahmed Elghazoul, Mr Anqi Chen

Sponsors: Health and Safety Executive (UK)

Background

Over the last few decades, there have been a number of major industrial accidents involving oil and gas installations worldwide. This includes the Buncefield event in the United Kingdom (UK) in 2005 where a major oil spill resulted in the formation of a large vapour cloud which ignited, resulting in an explosion and the biggest fire in the UK since the second World War.

Extensive damage subsequently occurred to both the plant and surrounding buildings due to much higher overpressures than would normally have been expected from a vapour cloud explosion of this nature. Surrounding buildings close to the site suffered severe structural damage.

Light damage could even be found at a distance of up to 1.5 kilometres from the site. In response to this event, a great deal of work was carried out on collecting and analysing available evidence from the incident in order to understand the explosion mechanism and estimate the overpressure levels within the gas cloud that formed.

Fig 1: Comparison of Digital scans of Boxes subjected to varying detonation pressure time histories with numerical models of varying complexity
Fig 1: Comparison of Digital scans of Boxes subjected to varying detonation pressure time histories with numerical models of varying complexity

This included a number of damaged steel switch boxes which could be used as overpressure indicators on the site located within the area covered by the vapour cloud which suffered varying degrees of damage. A series of tests were commissioned after the event in order to compare the damage of the field boxes with controlled static and dynamic tests on similar boxes.

The present work has focussed on numerical studies of the damaged steel boxes subjected to both detonation and deflagration scenarios and the assessment of the response of those boxes in order to aid the investigation of the explosion.

New Eulerian capabilites in the finite element package ABAQUS has been used together with exisiting Lagrangian formulation to create three numerical models with increasing complexity: (1) Pure Lagrangian model; (2) Uncoupled Eulerian – Lagrangian (UEL) model and (3) Coupled Eulerian – Lagrangian (CEL) model.

The study has also been extended to the response of a portal frame structure outside the gas cloud which suffered varying degrees of damage in order to try and provide some guidance on the safe siting of industrial type structures from oil storage facilities.