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Fire and Explosion

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Abstract

Compliance with new UK and EU gas safety legislation for chemical processing plants is today a major factor influencing its design and operation. The activities of exploration and production of natural gas are associated with gas transportation, distribution and storage. In industrial, commercial and domestic markets, there are innumerable combusting flows as gas is burned as an end product by customers. In all these activities, accurate assessment of what would happen in the event of an operational or accidental release of gas, particularly where gas dispersion, fire or explosion might be involved, is an essential part of ensuring safe operations.

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Reimpresión en el año 1989 Incluye bibliografía e índice
Understanding vapour cloud explosions-an experimental study”. 55th Autumn Meeting, The Institution of Engineering
  • R J Harris
  • M J Wickens
Vapor cloud explosion analysis, AIChE Loss Prevention Symposium
  • Q A Baker
  • M J Tang
  • E A Scheier
  • G J Silva
Vapour Cloud Explosion Blast Modelling
  • A C Berg
  • Van Den
  • C J M Wingerden
Utilisation of spill-return atomizer in health care
  • G G Nasr
  • A J Yule
  • T Hughes
An experimental study of the physics of gaseous deflagrations in a very large vented enclosure” 14th ICDERS Coimbra Portugal
  • B J Bimson
  • D C Bull
  • T M Cresswell
  • P R Marks
  • A P Masters
  • A Prothero
  • J S Puttock
  • J J Rowson
  • B Samuels
Explosion damage”, 6th International Meeting of Forensic Science
  • V J Clancey
The assessment of pressure hot water explosion sub pressure in system
  • Hse
  • Book
Industrial spray and atomisation
  • G Nasr
  • G Yule
  • A J Bendig