Title:
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The characterisation of vented dust explosions and their effect on structures
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The risk of dust explosions affects many industries. The range of particulate substances
that are explosible is very wide; it includes natural products such as grain dust and sugar,
synthetic materials such as pharmaceuticals and metal powders such as aluminium and
magnesium.
One of the earliest recorded dust explosions occurred in a Bakery in December 1785 and
it was not until the nineteenth century, that the mechanisms of dust explosions were
recognised and that research programmes were established to investigate this
phenomenon.
Explosion relief venting is a commonly used form of explosion protection, employed in a
wide range of industries, to protect vessels and production units from the overpressures
generated by dust or gas explosions. Considerable research has been undertaken on the
control of the internal explosion pressure by relief venting and this has resulted in the
production of a number of guidance documents for the use and sizing of explosion relief
vents. However, the safe use of explosion relief vents requires that buildings and process
plant be designed, constructed and sited in such a way that the pressure generated from
vented explosions will not cause unacceptable damage. In spite of this, there is very little
published guidance relating to the pressure and flames effects resulting from the vented
explosion and how their magnitude can be estimated and what measures should be taken
to minimise them.
Based on a full-scale experimental programme involving over three hundred vented Maize
starch and Coal dust explosions in chamber volumes of 20 m3 and 40 m3, this thesis
provides techniques for characterising the external effects of vented dust explosions and
assessing their effect on brick and steel structures in the surrounding environment.
The structural response and loading data was obtained by using both specifically
designed, brick and steel targets, which were representative of current UK building
design, located directly in-line with the vented explosions and by using buildings already
within the laboratory structure. In all cases these buildings were instrumented to provide
information on both their structural characteristics and response to applied loads. By using
this data comparisons were also made on the characteristics of the pressure time curves
observed in complex geometries located away from the direct venting line with the results
obtained in the direct venting line. Appendix A4 offers guidance to industry based on the
findings from this research.
Based on the results from the experimental study, a number of numerical techniques for
predicting the response of structures were assessed. This work showed that many of the
current methods were not applicable to this work as they were developed to study the
response of complex steel structures, unrepresentative of typical building designs,
subjected to relatively high pressure internal gas explosion loading scenarios.
The methods identified for predicting the response of brickwork buildings to explosions
were designed around vented gas explosions with simple impulse loading characteristics.
It has been shown that these tools were unable to predict the structural response of the
brickwork buildings to the vented dust explosions in this study with any degree of
accuracy although they appear to offer a basis for future development.
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