Special Issue—Fire and Explosion
1
0957–5820/04/$30.00+0.00 # 2004 Institution of Chemical Engineers www.ingentaselect.com=titles=09575820.htm Trans IChemE, Part B, March 2004 Process Safety and Environmental Protection, 82(B2): 87 EDITORIAL Special Issue—Fire and Explosion This issue of PSEP is devoted to fire and explosion. Fires and explosions have, of course, been central to safety in the process industries—and, indeed, to safety in all spheres of human activity—for a very long time indeed. In this issue, I am delighted to be able to introduce seven excellent papers covering 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 by Venart 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 fire loading on pressurized hydrocarbon processing plant and, specifically, its design and protection. Much of industry bases its approach on the recommended practices of the American Petroleum Institute (API). These recommendations are, however, restricted in their application. In particular, they apply to relatively small pool fires and were designed for use in (onshore) refineries, where plant is widely spaced, so that a fire is likely to impinge on only one vessel. Thus their applicability to more severe pool fires, jet fires and, for example, to offshore platforms, where plant is not widely spaced, has always been doubtful (and, to be fair, the API never intended that they should be so applied). What Roberts et al. have done is to show just how doubtful their applicability is, based on many experiments conducted over the last ten years. I think that the authors would be the first to admit that more experiments need to be done but they show quite clearly that actual heat fluxes can be much higher than the API recommendations would lead one to believe. The safety implications are obvious and important. The paper by Marshall and di Marzo deals with modelling the dynamics of sprinklers used to protect against fire. They discuss the fundamental physics (fluid mechanics, heat and mass transfer) of the processes involved so that appropriate CFD or other models can be developed. They note that the behaviour of the sprays from a sprinkler is strongly coupled with 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 at Flixborough in the UK in 1974 in which 28 people were killed. Of course, others have already investigated this disaster rather fully: the Court of Inquiry in its report of 1975 and many others including Ralph King since then. Although some may feel that Flixborough has been gone into more than enough, there is no certainty 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, Venart reanalyses the initial cause of the event and develops a two-step scenario: a first step involving failure of just one bellows, releasing perhaps 10–15 tonnes of cyclohexane, and then a second 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 that to describe this scenario as the cause of the disaster might be stretching a point: trigger might be a better word, inasmuch as the underlying or root cause was a lack of appropriate expertise in mechanical engineering in the design of the temporary pipework in place of the missing reactor. Thus, when Gavrilo Princips assassinated Franz Ferdinand in Sarajevo in 1914, he did not cause the First World War but, in a literal sense, he did trigger it. Notwithstanding this, the author has conducted a rather full analysis of the disaster, including use of computa- tional fluid dynamics and laser doppler velocimetry. Even if his proposed alternative scenario were to be wrong (and he does provide considerable evidence in its favour), there are valuable lessons for all of us here. The paper by Demichela et al. continues the theme of accident investigation and presents an analysis of an accidental release of 18 tonnes of LPG from a road tanker at Paese in Italy in 1996. This release led to an explosion involving up to about 1000 tonnes of LPG stored in other tanks: 2 people were killed and 5 were seriously injured. The authors simulate the sequence of events computationally as well as using experi- mental evidence based on a 50 metre diameter fireball produced by about 0.25 tonne of LPG. As with all such accident investigations, there is much for all of us to learn. As a change of tack, the paper by Pavey reviews the whole subject of electrostatic hazards in the process industries. It includes an overview of the fundamental underlying science. It discusses some ways in which electrostatic hazards can be addressed and then goes on to illustrate these by reference to a variety of realistic scenarios. The paper by Dastidar and Amyotte moves us to the area of dust explosions. In particular, they discuss use of the calcu- lated adiabatic flame temperature (CAFT). CAFT has already been shown to be a way of determining flammability limits for hydrocarbon gases. Here, the authors discuss how CAFT can be extended to determine these limits for mixtures of gaseous fuels, oxidizers and inerts and then show how it can be further extended to determine these limits for mixtures of solid fuels (such as dust) and inerts in air. They go on to show that their model is in agreement with (albeit, limited) experimental data. The final paper, by Shah et al., continues with the theme of solids combustion. They bring together the results of several recent studies on the burning of porous materials of low exothermicity that are, for whatever reason, exposed to a continuous heat source (a hotspot). Amongst other things, they develop new dimensionless criteria for ignition and also show that ignition is very different when exothermicity is low from when it is high. Covering their different areas and in their different ways, these seven papers all show that important understanding can be derived and lessons learnt from an area as old as fire and explosion—and also that there is still much to do. I am sure that you will get as much from the papers as I did. Professor Stephen Richardson Imperial College London, UK Subject Editor – Fire and Explosion 87
-
Upload
stephen-richardson -
Category
Documents
-
view
215 -
download
0
Transcript of Special Issue—Fire and Explosion
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
87
![Fire and Explosion Hazard Management[1]](https://static.fdocuments.net/doc/165x107/577cd7541a28ab9e789eb4df/fire-and-explosion-hazard-management1.jpg)
