0957–5820/04/$30.00+0.00# 2004 Institution of Chemical Engineers

www.ingentaselect.com=titles=09575820.htm Trans IChemE, Part B, March 2004Process Safety and Environmental Protection, 82(B2): 87

EDITORIAL

Special Issue—Fire and Explosion

This issue of PSEP is devoted to fire and explosion. Fires andexplosions have, of course, been central to safety in theprocess industries—and, indeed, to safety in all spheres ofhuman activity—for a very long time indeed. In this issue, Iam delighted to be able to introduce seven excellent paperscovering many aspects of the area:

� fires: the papers by Roberts, Buckland, Shirvill, Lowe-smith & Salater and by Marshall & di Marzo;

� accidents involving fires and explosions: the papers byVenart and by Demichela, Piccinini & Poggio;

� electrostatic hazards: the paper by Pavey;� dust explosions: the paper by Dastidar & Amyotte;� ignition of solids: the paper by Shah, Brindley, Griffiths,

McIntosh & Pourkashanian.

The paper by Roberts et al. deals with the issue of fireloading on pressurized hydrocarbon processing plant and,specifically, its design and protection. Much of industrybases its approach on the recommended practices of theAmerican Petroleum Institute (API). These recommendationsare, however, restricted in their application. In particular, theyapply to relatively small pool fires and were designed for usein (onshore) refineries, where plant is widely spaced, so that afire is likely to impinge on only one vessel. Thus theirapplicability to more severe pool fires, jet fires and, forexample, to offshore platforms, where plant is not widelyspaced, has always been doubtful (and, to be fair, the APInever intended that they should be so applied). What Robertset al. have done is to show just how doubtful their applicabilityis, based on many experiments conducted over the last tenyears. I think that the authors would be the first to admit thatmore experiments need to be done but they show quite clearlythat actual heat fluxes can be much higher than the APIrecommendations would lead one to believe. The safetyimplications are obvious and important.

The paper by Marshall and di Marzo deals with modellingthe dynamics of sprinklers used to protect against fire. Theydiscuss the fundamental physics (fluid mechanics, heat andmass transfer) of the processes involved so that appropriateCFD or other models can be developed. They note that thebehaviour of the sprays from a sprinkler is strongly coupledwith that of the fire itself, presenting an obvious and interest-ing challenge to the modelling.

The paper by Venart presents an analysis of the explosion atFlixborough in the UK in 1974 in which 28 people were killed.Of course, others have already investigated this disaster ratherfully: the Court of Inquiry in its report of 1975 and many othersincluding Ralph King since then. Although some may feel thatFlixborough has been gone into more than enough, there is nocertainty in an accident as complex as this one: of necessity,one is dealing with the balance of probabilities. As a result,there is still much that can be learnt. In this paper, Venartreanalyses the initial cause of the event and develops a two-stepscenario: a first step involving failure of just one bellows,releasing perhaps 10–15 tonnes of cyclohexane, and then asecond one involving detonation of the resulting vapour cloud,with an explosive effect equivalent to perhaps 280 tonnes of

TNT. Perhaps the only caution that I would make on this is thatto describe this scenario as the cause of the disaster might bestretching a point: trigger might be a better word, inasmuch asthe underlying or root cause was a lack of appropriate expertisein mechanical engineering in the design of the temporarypipework in place of the missing reactor. Thus, when GavriloPrincips assassinated Franz Ferdinand in Sarajevo in 1914, hedid not cause the First World War but, in a literal sense, hedid trigger it. Notwithstanding this, the author has conducted arather full analysis of the disaster, including use of computa-tional fluid dynamics and laser doppler velocimetry. Even if hisproposed alternative scenario were to be wrong (and he doesprovide considerable evidence in its favour), there are valuablelessons for all of us here.

The paper by Demichela et al. continues the theme ofaccident investigation and presents an analysis of an accidentalrelease of 18 tonnes of LPG from a road tanker at Paese inItaly in 1996. This release led to an explosion involving up toabout 1000 tonnes of LPG stored in other tanks: 2 people werekilled and 5 were seriously injured. The authors simulate thesequence of events computationally as well as using experi-mental evidence based on a 50 metre diameter fireballproduced by about 0.25 tonne of LPG. As with all suchaccident investigations, there is much for all of us to learn.

As a change of tack, the paper by Pavey reviews the wholesubject of electrostatic hazards in the process industries. Itincludes an overview of the fundamental underlying science. Itdiscusses some ways in which electrostatic hazards can beaddressed and then goes on to illustrate these by reference to avariety of realistic scenarios.

The paper by Dastidar and Amyotte moves us to the area ofdust explosions. In particular, they discuss use of the calcu-lated adiabatic flame temperature (CAFT). CAFT has alreadybeen shown to be a way of determining flammability limits forhydrocarbon gases. Here, the authors discuss how CAFT canbe extended to determine these limits for mixtures of gaseousfuels, oxidizers and inerts and then show how it can be furtherextended to determine these limits for mixtures of solid fuels(such as dust) and inerts in air. They go on to show that theirmodel is in agreement with (albeit, limited) experimental data.

The final paper, by Shah et al., continues with the theme ofsolids combustion. They bring together the results of severalrecent studies on the burning of porous materials of lowexothermicity that are, for whatever reason, exposed to acontinuous heat source (a hotspot). Amongst other things,they develop new dimensionless criteria for ignition and alsoshow that ignition is very different when exothermicity is lowfrom when it is high.

Covering their different areas and in their different ways,these seven papers all show that important understanding canbe derived and lessons learnt from an area as old as fire andexplosion—and also that there is still much to do. I am surethat you will get as much from the papers as I did.

Professor Stephen RichardsonImperial College London, UK

Subject Editor – Fire and Explosion

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