Igniter-induced hybrids in the 20-l sphere

Dust explosibility is traditionally described by two parameters, namely the maximum explosion pressure, P$_{max}$, and the deflagration index, K$_{St}$, usually determined through testing in a closed, pressure-resistant spherical vessel, either 20 L or 1 m$^{3}$ in volume. These parameters constitute key variables in the design of explosion protection systems, such as venting, suppression or isolation systems. The potential for overdriving dust combustion with pyrotechnical igniters in the 20-l sphere has been recognized, discussed and analyzed for many years, notably in the determination of the minimum explosible and limiting oxygen concentrations, which has led to specific guidelines regarding the ignition source strength in ASTM standards. The current paper presents new experimental evidence that the energy provided by pyrotechnical igniters may, in some instances, physically alter the dust being tested in the 20-l sphere. K$_{St}$ values can be several times greater in the small vessel compared to those measured in the 1-m$^{3}$ chamber. Further visual evidence is provided to show that high energy ignition can produce a turbulent flame region, possibly consisting of a hybrid mixture of flammable gas (or vapor) and dust, which can propagate faster than the corresponding pure dust. The experiments suggest that K$_{St}$ values measured in the 20-l sphere may no longer be representative of a dust deflagration in a real process environment. We recommend additional tests in a 1-m$^{3}$ chamber when a dust exhibits a low flash point, or when it's K$_{St}$ is above 300 bar m/s in the 20-l sphere.The authors gratefully acknowledge the support of Fike Corporation for their permission to publish this work

Explosion hazards of aluminum finishing operations

© 2017 Elsevier Ltd Metal dust deflagrations have become increasingly common in recent years. They are also more devastating than deflagrations involving organic materials, owing to metals' higher heat of combustion, rate of pressure rise, explosion pressure and flame temperature. Aluminum finishing operations offer a particularly significant hazard from the very small and reactive aluminum particles generated, and thus require high attention to details of operation and explosion safety management. This paper presents available statistics on metal dust explosions and studies the specific explosion hazards of aluminum finishing operations. The analysis of seven case studies shows that the proper design, monitoring and maintenance of dust collection systems are particularly important. Furthermore, the isolation of deflagrations occurring in dust collection systems, as well as good housekeeping practices in buildings, are critical safeguards to avoid the occurrence of catastrophic secondary explosions

Explosion hazards of aluminum finishing operations

Metal dust deflagrations have become increasingly common in recent years. They are also more devastating than deflagrations involving organic materials, owing to metals' higher heat of combustion, rate of pressure rise, explosion pressure and flame temperature. Aluminum finishing operations offer a particularly significant hazard from the very small and reactive aluminum particles generated, and thus require high attention to details of operation and explosion safety management. This paper presents available statistics on metal dust explosions and studies the specific explosion hazards of aluminum finishing operations. The analysis of seven case studies shows that the proper design, monitoring and maintenance of dust collection systems are particularly important. Furthermore, the isolation of deflagrations occurring in dust collection systems, as well as good housekeeping practices in buildings, are critical safeguards to avoid the occurrence of catastrophic secondary explosions.Fluid MechanicsChemE/Delft Ingenious Desig

Metal dusts explosion hazards and protection

Copyright © 2019, AIDIC Servizi S.r.l. Many industrial processes handle, use, or produce metallic particles small enough to explode in air, thus posing severe explosion hazards. Finishing operations, for example, create very fine particles and have been involved in a growing number of accidents in recent years. New emerging processes, such as 3D printing, are being rapidly developed and directly use micrometric particles to create complete objects by welding layers of material together. Finely divided metals also enter into the composition of plastics, rubber, fibers, paints, coatings, inks, pesticides, detergents, and even drugs; additionally, they are used as catalysts for major industrial chemical reactions, and are even being explored as possible clean alternatives to fossil fuels. Metal dusts are of special concern due to their peculiar combustion properties, including their higher heat of combustion and pyrophoric nature,. As a result, metal dusts explosions are often much more devastating than explosions involving organic materials. Additionally, due to their high reactivity, many fine and most ultra-fine metal powders can burn in carbon dioxide, water vapor and even nitrogen. Whereas preventive measures may reduce explosion risks efficiently, they rarely are sufficient to eliminate explosions completely, especially when dealing with highly reactive metallic particles. Therefore explosion protection measures usually also need to be considered. The high energetic content of metal dusts poses new challenges to conventional explosion protection systems in terms of robustness and response time. This paper reviews the special hazards of metal dusts and presents the state-of-the-art in terms of explosion protection

Dust Explosion Propagation in Small Diameter Pipes

© 2018 American Institute of Chemical Engineers In facilities handling combustible dusts, the isolation of propagating deflagrations requires great attention due to the potential catastrophic consequences of secondary dust explosions. While the ability of dust explosions to propagate is widely recognized, some misconceptions still exist. One of the common myths is that a dust explosion cannot propagate through small diameter pipes and that explosion isolation may not be required in that case. This article first presents a simplified theory of flame propagation in pipes. Dust explosion experiments performed in industrial-scale pipes smaller or equal to 4 in (or 100 mm) in diameter are then reviewed. The findings of the experiments are interpreted in the light of the simplified theory. Our study reveals that dust explosion propagation has been consistently observed in pipes with a diameter as small as 1 in. While the likelihood of flame propagation seems to decrease with pipe diameter and other “chemical” and “engineering” factors, it remains a realistic scenario and therefore should be addressed in the design and operation of powder handling systems. © 2018 American Institute of Chemical Engineers Process Saf Prog 2018.Fik

An integrated approach towards safety during change in the chemical process industry

Increasing global competition and shareholder pressure cause major changes in the chemical industry. Over the last decade companies continuously improve their manpower efficiency. As a result most chemical plants of today can be regarded as lean plants. Plans to further reduce the number of staff are increasingly criticised by the personnel for safety reasons. This may cause strong resistance to further staff reductions. It is obvious that management and workers may have conflicting points of view (not only over safety issues), but also technologists and safety engineers may have specific points of view. With the TNO approach of Safe manpower change it is possible to tackle this issue with all process stakeholders concerned

Risico- en veiligheidsmanagement in high-tech-high-hazard sectoren, van Clapham Junction tot Macondo, Deepwater Horizon: een overzicht van Engels- en Nederlandstallige literatuur. Deel 4: de periode 1988-2010- de industriële high-tech-high-hazard sectoren

Vraagstelling: Wat is de invloed geweest van algemene ma- nagementstromingen en van onderzoek naar de oorzaken van ongevallen en rampen op het managen van veiligheid? Binnen welke context heeft deze ontwikkeling plaatsgevon- den en wat is de invloed geweest op het veiligheidskundige vakgebied? Methode: Het literatuuronderzoek heeft zich beperkt tot oorspronkelijke Engelstalige en Nederlandstalige artikelen en documenten uit de wetenschappelijke literatuur in de periode 1988-2010. Resultaten en conclusies: In deze periode worden bekende theorieen, modellen en metaforen ontwikkeld of heruitge- geven; de High Reliability Theory, heruitgave van Man de Made Disasters met de Distaster Incubation Theory en de heruitgave van de Normal Accident Theory. Ook krijgt de Zwitserse kaas metafoor zijn definitieve vorm, wordt de bowtie gepubliceerd en de Drift to danger-metafoor. Al deze theorieen, modellen en metaforen benadrukken de organisatorische aspecten van majeure ongevallen in de high-tech high-hazard sectoren. Algemene management- stromingen benadrukken het belang van externe stakehol- ders van bedrijven. Die invloed komt alleen in de Drift to danger-metafoor tot uiting. Organisatie/veiligheidscultuur en risico/veiligheidsma- nagement nemen in deze periode een vlucht, zowel in onderzoek als in consultancy-activiteiten bij bedrijven. Of dit veel op zal leveren is de vraag, gezien de onduide- lijke relatie met het veiligheidsniveau van bedrijven. Verder laat onderzoek bij bedrijven zien dat er vaak sprake is van sloppy management, resulterend in een onvoldoende zicht op mogelijke rampscenario's. De context van de ontwikkelingen is dynamisch. De terugtrekkende overheid valt samen met een markt- en technologie-ontwikkeling die in conflict kan komen met eisen die op grond van de noodzaak van veiligheid aan high-tech-high-hazard bedrijven worden gesteld

From Clapham junction to Macondo, Deepwater Horizon: Risk and safety management in high-tech-high-hazard sectors: A review of English and Dutch literature: 1988 - 2010.

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