Comment mettre en place des évents d'explosion ?

National audienceEn France, la technique des events d'explosion est tres largement employee, bien connue et bien acceptee dans de nombreux secteurs de l'industrie. Compte tenu de l'importance du sujet, il parait necessaire de lui consacrer une place specifique dans ce seminaire d'autant plus que nombre de guides de dimensionnement d'events sont aujourd'hui publies et peuvent presenter des contradictions. L'objet de cette presentation est de faire une mise au point. Dans un premier temps, nous expliquons ce qu'est un event et la maniere dont il fonctionne (principes et parametres). Ensuite, nous dressons un bref historique qui permet de mettre les differentes methodes en perspective. Puis, nous resumons les developpements actuels et precisons enfin la maniere dont les choses pourraient finalement evoluer en vue d'une methode europeenne unifiee dans les prochaines annees

Experimental determination of the maximum flame temperatures and of the laminar burning velocities for some combustible dust-air mixtures

International audienceIn view of the possible consequences of a dust explosion, it is acknowledged that there is a need for assessing the reliability 'of the tools used to assess the explosion hazard and of the protection method. Surely for this, a better understanding of the mechanisms of dust explosion development is compulsar

EFFEX : a tool to model the consequences of dust explosions

International audienceSome accidents, such as the explosion of the silo in Blaye in August 1997, remind us that explosions of combustible dust can have serious consequences, not only for the industrial installations concerned but also for the environment. The necessity of being able to estimate the effects of an explosion of this type became apparent at the beginning of the 1990s. Owing to the complexity of this subject which involves the mechanical resistance of structures, flame propagation and fluid mechanics, etc., a simulation tool clearly had to be developed. It was in these circumstances that EFFEX was developed. EFFEX is not a software based on the discretization of space but it solves differential equations, each variable of which is considered to be a time function. This is therefore an "integral" type of software code. It is made up of a set of eight modules covering the characterisation of the explosion conditions, the estimation of the mechanical behaviour of the containment and the evaluation of the consequences. Comparison of the results for each of the main modules shows satisfactory consistency with available experimental results. Trials using EFFEX to simulate past accidents, including the transmission and reinforcement of the explosion between subsequent volumes, in order to verify the satisfactory linking of the various modules gave results that were similar to the actual consequences. Several tens of calculation were made so far on silo type of equipments and a synthesis is proposed in addition to a general description of the software

Toward modelling of frictional ignition

International audienceThis work is part of a European sponsored project named MECHEX (GRD2-2000-30035) which aims at providing a new insight and data about the ignition hazard induced by mechanical contacts classically termed as "grinding", "friction" and "impact" so that some sort of classification of mechanical equipments against this specific hazard could be issued. "Friction" and "grinding" might be understood as continuous mechanical solicitation whereas "impact" would be referred to as an instantaneous action such as that of a flying object striking freely on a fixed target. Within that scope, we undertook a detailed physical analysis of possible ignition mechanisms on the basis of precise measurements of hot spots, temperatures and fragments and tried to link them to the thermomechanical properties of the contacting bodies

Analysis of ignition risk on mechanical equipment in ATEX

International audienceUntil the implementation of the ATEX directive 94/9/CE, the certification of equipment intended to explosive atmospheres was only dedicated to electrical equipment. Since the 1st July 2003, the non-electrical sources of inflammation are also to be looked at before putting an ATEX equipment on the market (pumps, couplers, reducing gears, ...). Among these sources, mechanical friction and impacts are a main cause of ignition of explosive atmosphere. The risk analysis of the equipment consists in considering the failures, which can lead to ignition. If the failure involves a friction between two parts or an impact, we shall estimate if this friction or impact dissipates a sufficient amount of energy to ignite the surrounding explosive atmosphere. As part of the European program MECHEX, we have studied the process of degradation of the mechanical energy into heat during friction and impacts and we have examined the mechanisms of ignition at the contact zone. An extensive experimental program is presented and some 'simple' modelling is proposed on purpose of practical applications. For frictional situations, a critical rubbing power is calculated without any limitations as for a potential lower boundary concerning the rubbing velocity. For 'impacts', the relevant parameter for ignition is not the kinetic energy of the projectile but its velocity and the nature of the materials

Evolution des méthodes de protection des procédés industriels contre les effets des explosions : le projet DELFINE)

National audienceClassical methods for vent sizing are based on experimental correlations coming from academic test situations, sometime quite different from real industrial conditions. Thus, they do not take into account the variation of turbulence in industrial enclosures, which may alter drastically the explosion violence. The DELFINE installation presently in construction will allow studying dust explosions in real working conditions of a dust collector. Preliminary experiments in an instrumented small size filter are presented, which allow characterizing the turbulence level in every work phase of the system. It appears that the turbulence level is generally lower than in the standard conditions for vent testing, even during reverse jet cleaning. It should offer perspective for optimization of the venting areas for dust collectors. Explosion tests in real conditions on the DELFINE installation will be performed to try to confirm these first observations.Les industries de la chimie, du bois et de l'agroalimentaire concentrent plus de 80% des explosions de poussières recensées en France au cours des 100 dernières années [1]. Pour cette raison il existe aujourd'hui un secteur industriel qui propose des solutions de maîtrise des risques d'explosion de poussière et met sur le marché, qui des technologies de protection, qui des appareils équipés de ces technologies dès la conception. Si des normes relatives à ces stratégies industrielles ont été proposées comme pendant à la Directive ATEX [2], il a été observé qu'elles étaient loin de couvrir la réalité des procédés industriels. Cela est perçu comme un obstacle majeur à l'ingénierie de la sécurité des procédés puisqu'on ne possède pas de " méthodes d'ingénieur " suffisantes. L'objectif du projet DELFINE qui réunit les moyens de FIKE Corp. (producteur de systèmes de protection), de DELTA NEU (producteur de process industriels de filtration) et de l'INERIS (Expert de la phénoménologie de l'explosion) est de promouvoir des méthodes de dimensionnement des systèmes de protection en commençant par la technologie des évents. On présente dans cette communication les résultats obtenus au plan de la modélisation phénoménologique du développement des explosions dans les systèmes industriels (réseaux d'enceintes et de canalisations) et les premiers résultats expérimentaux obtenus à l'échelle réelle au moyen d'une boucle d'essai de dépoussiérage spécialement conçue pour le projet

Processes of the formation of large unconfined clouds following a massive spillage of liquid hydrogen on the ground

International audienceBecause of hydrogen low volumetric energy content under its gaseous form, transport and storage of liquid hydrogen will certainly play a major role in any future hydrogen economy. One of the obstacles to the expected development use of hydrogen is the poor state of knowledge on explosion risks in the event of an extensive spillage. INERIS set up a large-scale experiment to study the mechanisms of the formation of the gas cloud resulting from such a spillage and the associated mixing process and turbulence effects

Laser ignition of dust clouds

International audienceIn a previous paper [1], the possibility of igniting a combustible dust-air mixtures by a light beam in contact with a substrate made of an inert matter and heated by a light beam was investigated. The objective of the present work is to produce more data on the subject. The available results suggest a strong similarity between combustible dust-air mixtures and explosible gas-air mixtures within the scope of the investigated ignition phenomena. In particular a relationship between the standard ignition temperature of dust clouds and the temperature of the target at the minimum incident power at ignition (continuous irradiation) has been highlighted which seems to be similar to the one obtained for gases. If confirmed, this would imply that the knowledge of these standard parameters would help in predicting the danger of igniting any kind of explosible mixtures including hybrid mixtures (combustible gas-combustible dust-air) or oxygen depleted/enriched mixtures