{"id":32510,"date":"2024-01-02T15:14:02","date_gmt":"2024-01-02T13:14:02","guid":{"rendered":"https:\/\/obera.fr\/advice\/dust-removal-process-and-risk-of-explosion-or-fire\/"},"modified":"2025-04-15T10:22:26","modified_gmt":"2025-04-15T08:22:26","slug":"procede-depoussierage-risque-explosion-incendie","status":"publish","type":"post","link":"https:\/\/obera.fr\/en\/our-tips\/procede-depoussierage-risque-explosion-incendie\/","title":{"rendered":"Dust removal process and risk of explosion or fire"},"content":{"rendered":"\n

Dust collectors<\/strong> are used to prevent the risk of fire and explosion in industrial processes involving the suspension of very fine particles. But these risks are often transferred to the dust collection system, which sucks up and filters combustible dust. Preventive and protective<\/strong> measures must therefore also be applied to the dust collection system<\/strong>.<\/p>\n\n

\"Explosion<\/figure>\n\n

Operating principles of the different types of dust collectors<\/h2>\n\n

Dust collectors<\/strong> are divided into dry (cyclones, bag filters, bag filters or cartridge filters, electrostatic precipitators) and wet (electrostatic precipitators) types.<\/p>\n\n

Cyclones use centrifugal force<\/strong> to separate dust from the air that carries it. From top to bottom, they take on a cylindrical, then truncated cone shape. At the top of the upper cylinder is the dusty air inlet, tangent to the cyclone circumference. Incoming dusty air rotates around the walls as it descends, separating from the coarser particles by gravity. Then, through the center of the cyclone, the air rises to the top where the outlet is located. Coarse dust accumulates at the bottom of the cone and is discharged via an extraction device<\/strong> (double flap, sluice or rotary valve). At the outlet, the air still contains the finest dust, which only a bag or cartridge dust collector can remove.<\/p>\n\n

A bag, cartridge or pocket filter dust collector works on the same principle as a domestic vacuum cleaner. Each filter sleeve, pocket or cartridge stops dust on its surface and allows dust-free air to pass through. A dust collector is made up of two parts: one part receives the dusty air from the dust collection device; the filter sleeves retain the dust while allowing air to pass through. A hopper at the bottom of the dusty section collects the dust accumulated in the sleeves, which is then released during each cleaning operation<\/strong> (shaking, compressed air jet). The hopper is emptied into a sealed container or via a rotary valve. In the other part, the dedusted air exits the filter and is directed into a duct, where a fan draws in the airflow, expelling it or reintroducing it into the room.<\/p>\n\n

An electrostatic precipitator<\/strong> (or electrofilter) works on the mutual attraction of two elements with opposite electrical charges. The industrial dust collector<\/a> negatively charges suspended dust in the air stream. This is achieved by passing it through a network of high-voltage wires (anode). The dust then separates from the air stream by being attracted to positively-charged walls (cathode), to which it attaches itself. Accumulated dust is then removed from the cathodes by hammering or water cleaning<\/strong>. The dust is collected in a hopper.<\/p>\n\n

A wet dust collector passes the dust-laden air stream through a column of water (bubbling), or a curtain of trickling water, or a mist of counter-current water spray. The dust adheres to the water molecules and separates from the air.<\/p>\n\n

<\/p>\n\n

The risk of fire or explosion in a dedusting installation<\/h2>\n\n

Risk of ATEX formation<\/h3>\n\n

For ATEX to form in a cyclone<\/strong>, both the dust level in the air stream must reach the explosive range, and the percentage of fine particles must be sufficient. Coarse particles have a cooling effect on the flame, preventing it from spreading when they are abundant.<\/p>\n\n

The dust-laden air stream passing through the ducting enters the dust-laden air collector up to the baghouse body, and may constitute an ATEX if the dust concentration in the air stream is within the explosive range<\/strong>. In this case, ATEX will enter the dust collector. <\/p>\n\n

\"Atex<\/figure>\n\n

The formation of an ATEX can be temporary. Depending on the process, the level of dust in the air flow in the duct may vary over time. Indeed, the rate of emission of combustible particles during the operation of a device may not be constant, particularly during process start-up or shutdown, discontinuous operations, operating phases, etc. Pneumatic cleaning of sleeves or cartridges<\/strong> generally produces ATEX, as the finest particles are re-suspended by the cleaning process, and moreover, potentially when the unit is shut down (end-of-cycle cleaning).<\/p>\n\n

When a wet dust collector is used to filter air laden with metal particles (aluminum in particular), there’s a risk of a chemical reaction between the water and the metal, producing hydrogen. The nature of the metal influences the reaction kinetics, and during normal operation of the dust collector, the hydrogen emission rate is insufficient. When the dust collector is shut down, hydrogen can build up in the canopy, creating an ATEX hazard. On the other hand, wet dedusting<\/strong> generally remains the safest dedusting principle from an ATEX point of view, as ignition sources are generally extinguished by the action of water.<\/p>\n\n

Risk of ATEX ignition and explosion<\/h3>\n\n

The passage of dust-laden air through the pipe is subject to electrostatic charging of the dust as it rubs against the pipe wall. This phenomenon can also occur in the dust section of dust collectors. Electrostatic discharge may occur in the pipe or in a dust collector. The energy it releases is estimated at less than 10mJ. If the energy released exceeds the minimum ignition energy of the dust in suspension, the electrostatic discharge will be their source of ignition<\/strong>, resulting in an ATEX explosion in the duct or in the dust-laden part of a baghouse.<\/p>\n\n

The electrostatic precipitator operates on the potential difference between the anode and cathode. As a result of the intensity of this difference, the distance between the electrodes must be adjusted to avoid the formation of an electric arc (breakdown), the source of ignition of an ATEX.<\/p>\n\n

A process can emit both dust and glowing particles (grinding, milling, etc.). The latter can be a source of ignition for an ATEX present in the dust area or in the filter bags of a dust collector<\/strong>. In this case, a wet dedusting solution is generally preferred, or dry dedusting with spark pre-separation and a spark detection and extinguishing device.<\/p>\n\n

Fire hazard<\/h3>\n\n

Accident experience shows that anexplosion in a baghouse<\/strong> is often followed by a fire in the dust deposited at the bottom of the hopper and in the filter, and consequently in the filter itself. <\/p>\n\n

Filtration of dusty air does not heat up the dust. There is therefore no risk of fire in filter dust collectors due to self-heating, except in special cases where the substances captured at ambient temperature <\/strong>have a critical self-heating volume. When the volume at the bottom of the filter exceeds this, the risk of fire becomes obvious.<\/p>\n\n

ATEX prevention and protection measures for dust collectors.<\/h2>\n\n

Preventive measures by type of dust collector<\/h3>\n\n

The fire and explosion<\/a> prevention measure for baghouse dust collectors consists in suppressing electrostatic discharges by using antistatic bags. However, accident studies show that failure to ground such filters can lead to electrostatic discharges in excess of the minimum ignition energy<\/strong> of common dusts. This malfunction would lead to a higher level of danger than non-antistatic bag filters.<\/p>\n\n

In the case of a baghouse, regular inspection of the bags for wear, loosening or perforation is part of ATEX prevention. Checking inlet\/outlet pressures and fitting an opacimeter in the dust-free zone enable us to verify the tightness of the sleeves<\/strong>.<\/p>\n\n

To avoid electrostatic hazards being a source of ignition, all metal parts of the baghouse must be earthed, including piping. The same applies to the cyclone. Electrical components inside the dust collector must also comply with ATEX regulations. <\/p>\n\n

One preventive measure against glowing particles is to install a dust pre-separator before the main dust collector, either in the form of a cyclone, an impact separator or a spark detection and extinguishing<\/strong> device.<\/p>\n\n

In the case of an electrostatic precipitator, regular checking of the potential difference setting, and the distance between the electrodes, will prevent the risk of electric arcing.<\/p>\n\n

\"dustomat<\/figure>\n\n

Preventing ATEX explosions <\/strong>in wet-voice dust collectors involves: ventilating the volume when the unit is shut down to prevent hydrogen buildup; detecting hydrogen in the dust collector canopy. This type of dust collector is best installed outdoors, to dilute the presence of hydrogen, or in a room equipped with ventilation specifically designed for the risk of explosion. There is a risk of fire in the heating elements used to freeze the wet dust collector. The immersion of these resistors must be checked.<\/p>\n\n

<\/p>\n\n

Protective measures<\/h3>\n\n

Protective measures include : <\/p>\n\n

    \n
  • Equipping the dust collector with explosion vents<\/strong>: part of the wall of the dust collector, opening as soon as the overpressure resulting from the internal explosion of the ATEX begins, to evacuate the gases and the overpressure.<\/li>\n\n\n\n
  • The use of explosion suppressors<\/strong>: a device that detects the onset of an explosion inside the dust collector, prevents the explosion from reaching its maximum overpressure by injecting an extinguishing agent, and protects the walls of the dust collector from bursting. <\/li>\n\n\n\n
  • Decoupling the dust collector<\/strong> from the rest of the plant to prevent an explosion in the dust collector from spreading to the pipes. A valve that closes automatically under the effect of the pressure wave (ATEX check valve or quick-closing valve) must be installed on the pipes connecting the dust collector.<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"

    Dust collectors are used to prevent the risk of fire and explosion in industrial processes involving the suspension of very fine particles. But these risks are often transferred to the dust collection system, which sucks up and filters combustible dust. Preventive and protective measures must therefore also be applied to the dust collection system.<\/p>\n","protected":false},"author":4,"featured_media":81599,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_seopress_robots_primary_cat":"none","_seopress_titles_title":"Dust removal process and risk of explosion or fire","_seopress_titles_desc":"No risk of explosion or fire thanks to the dust removal process. Comply with safety standards and work regulations.","_seopress_robots_index":"","footnotes":""},"categories":[309],"tags":[18],"class_list":["post-32510","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-our-tips","tag-entete-small","generate-columns","tablet-grid-50","mobile-grid-100","grid-parent","grid-50","no-featured-image-padding","resize-featured-image"],"acf":[],"_links":{"self":[{"href":"https:\/\/obera.fr\/en\/wp-json\/wp\/v2\/posts\/32510","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/obera.fr\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/obera.fr\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/obera.fr\/en\/wp-json\/wp\/v2\/users\/4"}],"replies":[{"embeddable":true,"href":"https:\/\/obera.fr\/en\/wp-json\/wp\/v2\/comments?post=32510"}],"version-history":[{"count":3,"href":"https:\/\/obera.fr\/en\/wp-json\/wp\/v2\/posts\/32510\/revisions"}],"predecessor-version":[{"id":82189,"href":"https:\/\/obera.fr\/en\/wp-json\/wp\/v2\/posts\/32510\/revisions\/82189"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/obera.fr\/en\/wp-json\/wp\/v2\/media\/81599"}],"wp:attachment":[{"href":"https:\/\/obera.fr\/en\/wp-json\/wp\/v2\/media?parent=32510"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/obera.fr\/en\/wp-json\/wp\/v2\/categories?post=32510"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/obera.fr\/en\/wp-json\/wp\/v2\/tags?post=32510"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}