Combustible dust

Explosive dust or potentially explosive atmospheres occur in a wide variety of workplaces

Due to the fact that combustible dust from most organic materials, synthetic materials and metals can explode, attention needs to be given to prevent dust explosions. The European Community passed two directives on explosive atmospheres / combustible dust (called the ATEX directives), which came into effect on 1st July 2003 and July 1st 2006.

The application of these two directives has led to increased protection against explosions, making various technical and organisational actions obligatory. As leading experts in industrial air filtration, Nederman develops ATEX compliant products that fulfill the highest safety requirements.

Compliance with additional requirements in accordance with national or local government regulations are the responsibility of the local Nederman sales company and the customer.

Nederman offers dust extraction systems fulfilling the ATEX demands:

The explosion strength of the filter has been proven
ATEX compliance is ensured by means of explosion relief doors or panels
The risk of an explosion spreading may be prevented by installing safety equipment such as rotary valves, back pressure flaps, etc.
Fans are ATEX certified for handling potentially explosive dust.

Handling combustible dusts

End user responsibility

It is the owner/end user’s responsibility to determine the possible explosion risk in his premises. One of the obligations is to classify the areas where explosive atmospheres may occur. Another obligation of the owner/end user is to develop an “Explosion Protection Document”, that demonstrates amongst other:

Explosion risk and assessment
Adequate measures will be taken to attain the aims of the directive
The areas that have been classified into “zones”
That the workplace equipment is operated and maintained with due regards for safety

Only when the end user has declared the zones, will it be possible for the Nederman sales person to determine whether Nederman can provide the machinery and equipment required. The Nederman sales person will need the following data from the customer who will be the owner and end user of the equipment.

The ATEX zone classification of the areas into which the equipment will be installed. This is the responsibility of the end user
The properties of the dust to be handled, including its explosion class St1, St2 or St3.

ATEX zone classifications

Zone 20: A place in which an explosive atmosphere in the form of a cloud of combustible dust in air is present continuously, or for long periods or frequently. Examples: In general these conditions arise only inside equipment such us pneumatic conveying lines, mills, dry mixers, sieves etc. Zone 20 atmosphere is typically found inside equipment.

Zone 21: A place in which an explosive atmosphere in the form of a cloud of combustible dust in air is likely to occur in normal operation occasionally. Examples: In general, these conditions can arise where dust clouds are frequently present during normal operation, e.g. grinding, sanding, open charging etc. The extent of zone 21 atmosphere is typically a distance of 1 meter around the source of release. Human beings typically find it extremely difficult to breathe in zone 21 atmospheres.

Zone 22: A place in which an explosive atmosphere in the form of a cloud of combustible dust in air is not likely to occur in normal operation but, if it does occur, will persist for a short period only. Examples: In general, these conditions can arise in places with dust lying on the floor and other surfaces which can be dispersed and form explosive dust clouds. Normally, a manned area or an area close to people is most likely to be a no-zone (safe – non hazardous) area. For the general area to be classified even as Zone 22 there could be considerable deposits of dust lying on surfaces. Zone 22 atmosphere can occur in places where dust can escape through leaks and form hazardous quantities, in bag storage areas (bag breakage) etc. The extent of zone 22 atmosphere is typically a distance of 1 m (3.28 ft) around the source of release.

Manufacturer’s responsibility

It is the manufacturer’s responsibility to state the ATEX category of the machinery and equipment produced by the manufacturer. Products are categorized 1D, 2D and 3D with category 1D meaning the product employs a very high level of protection (zone 20, 21, or 22); category 2D, a high level of protection (zone 21 or 22); category 3D, a normal level of protection (zone 22). The Nederman symbol for products suitable for handling explosive dusts is DX or Z.

If Nederman as the manufacturer determines that the equipment/filter unit etc. is intended to be installed in a classified area, the equipment must be marked according to the ATEX directive (94/9/EC).

Above is an example of how Nederman equipment can be marked. Ex in a hexagon is the explosion protection symbol, followed by equipment group II (non mining), category 3D for Dust (D). Protection by constructional safety is represented by the “c”. Max surface temperature 125°C (257 °F).

Nederman Customization of Products

Product customization can be done by Nederman as long as it does not jeopardize the safety (risk assessment) of the product. Enlarging the total volume and/or area of the filter unit could put the strength of the product at risk. Additional electrical components or similar equipment representing an ignition source must be categorized if they are to be placed in a hazardous area.

Dust classification

The very same dust normally becomes more “explosive” the smaller the dust particles become. Therefore the properties of the dust to be handled in the Nederman equipment are of great importance. The specific KSt value or St class of the dust must therefore be provided by the customer. The KSt value is the maximum rate of explosion pressure rise in a 1 m³ (35,3 ft³) container. St classes are categories into which dusts are classified on the basis of their KSt values.

Dust explosion class	KSt , bar m/s (psi ft/s)
St 1	> 0 to 200 (0–61)
St 2	> 200 to 300 (61–91)
St 3	> 300 (91)
Table 1: St classes

Nederman equipment installed outdoors is suitable for explosive dusts of class St1 or St2. The equipment is not suitable for gas, chemical instable dusts or materials that self ignite, e.g. magnesium.

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Proven solutions

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Welding and cutting Welding fume & smoke extraction and thermal cutting extraction for sound, safe and efficient welding and cutting processing industries. This protects both the welder and the other workers. Explore	Woodworking industries Woodworking in the form of sawing, planing, sanding and other operations involves very large amounts of sawdust and sanding dust. To handle these large flows of wood waste safely and efficiently, Nederman has developed a wide range of products and systems based on filters, piping / ducting, fans, conveyors, silos and automated control systems. Explore

Products that solve: Combustible dust

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ATEX approved vacuums

426A Ex industrial vacuum cleaner

Vacuum cleaner for extraction of industrial waste and powders

Combustible dust

Explosive dust or potentially explosive atmospheres occur in a wide variety of workplaces

Nederman offers dust extraction systems fulfilling the ATEX demands:

Handling combustible dusts

End user responsibility

ATEX zone classifications

Manufacturer’s responsibility

Nederman Customization of Products

Dust classification

Composite machining

Foundry solutions for dust and fume extraction

Metal machining

Vehicle Repair Shops

Welding and cutting

Woodworking industries

Products that solve: Combustible dust

426A Ex industrial vacuum cleaner

510A Ex wet and dry vacuum

216A Ex Combustible Dust collector

105A Ex explosion proof dust collector

FilterMax DX ATEX cartridge dust collector

MJC mini compact cartridge dust collector

MHVF cartrige dust collector

FMC cartridge dust collector

E-PAK Fume and Dust Collector

FlexPak Dust and Fume Collector

NC cyclone

NEX DX Dust and Gas Extraction Arm

NEX D combustible dust extractor

NEX S Dust and Gas Extraction Arm

On tool dust extraction

Auto M-Z bag dust collector

CJ Cyclofilter bag dust collectors

FD flat bag dust collector

QuickFit clamp together ducting

CARZ back-pressure flap valve

NFKZ 3000 bag dust collector with chain conveyor

Flexfilter Ex

FS flat bag dust collector

CS round bag dust collector

VAC two stage vacuum fan

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Nederman USA - Thomasville