dust explosion protection

8/7/2019 dust explosion protection

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Cooper Crouse-Hinds GmbH your partner for dust explosion protection


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Dust Explosion Protection What is it?

One spark can be enough!

It is a generally known fact that

combustible gases can form poten-tially explosive mixtures. However,

more often than not, the fact thatcombustible dusts also represent alarge hazard source is not taken intoconsideration.

How do dust explosions occur?Whenever an ignitable mixture ofcombustible dust and air occurs, it

can be ignited by an ignition source,whereby, depending upon theircomposition, the dust-air mixtures

are more or less likely to ignite.The ignition of the mixture can resultin a chain reaction, during which

further explosions can be set offdue to dust being stirred up. Asthe amount of energy released can

be extremely high, the damagepotential of dust explosions is oftenenormous.

How can dust explosionsbe avoided?Together with constructionaland organisational measures, the

explosion risk can be minimizedby the choice of suitable, approvedapparatus for use in potentially

explosive dust atmospheres. TheCooper Crouse-Hinds GmbH offersa comprehensive range of electricalapparatus for safe use in potentially

explosive dust atmospheres.

Dust Ex zone subdivision:Zone 20: A place in which an explosi-

ve atmosphere in the form of a cloudof combustible dust in air is presentcontinuously, or for long periodsor frequently (p. e. inside a filling

hopper).

Zone 21: A place in which an explosi-ve atmosphere in the form of a cloud

of combustible dust in air is likelyto occur in normal operation occasio-nally (p. e. immediate vicinity of

hopper; normally in a radius of 1 m)

Zone 22: A place in which an explo-

sive atmosphere in the form of acloud of combustible dust in air isnot likely to occur in normal operationbut, if it does occur, will persist for a

short period only.

When assessing the safety aspectsof installations with a potentially

explosive dust atmosphere, numbersrelating to the ignition temperatures ofdust layers and ignition temperature

of clouds present an important meansfor the prevention of explosions.The BIA Report, Combustion and

Explosion Characteristics of Dusts,issued by the Association of Com-mercial and Industrial Workers Com-

pensation Insurance Carriers containsimportant information on this.

Where can dust explosions

occur?Combustible and, therefore, poten-tially explosive dusts occur moreoften than you think:

For example, during theprocessing of Organic products such as wood

and fibrous materials Foodstuffs, alcohol, tobacco and

animal foods Coal Metals and metal alloys

Technically, however, chemicalproducts made of plastic, resin and

rubber can also produce combustibledusts and, as a result, potentiallyexplosive atmospheres.

With combustible dusts it is alsonecessary to take the possibility ofglow fires due to dust layer into

account. The temperature required forthe ignition of the dust layer is general-

ly lower than the ignition temperatureof a dust/air mixture.

Zone 21

Zone 20

Subdivision of potentially explosive dust atmospheres

into zones by way of example of a Bag emptying station

without exhaust ventilation (Example see EN 61241-10

App. A)


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Electric drivesand lighting

Mills, mixers and conveyor systems indust Ex atmosphers: shall all be inexplosion-protected design and theyall depend on electric power - reliable,

safe and explosion-protected. TheCooper Crouse-Hinds GmbH hasdust explosion-protected switches,

intermediate motor terminal boxesand plugs and sockets for the safepower supply of your drives.

And not only that: the drives can beisolated from the mains easily andvisibly simply by means of plugs and

sockets. This makes the maintenanceand servicing of your installationsparticularly safe and easy.

Potential hazards can only be deter-mined and accidents prevented if thevisibility is good. Therefore, in particu-lar in areas where dust is produced,

safe illumination is absolutely essenti-al. Dust explosion-protected luminai-res and floodlights provide reliable

lighting here, while, even in the eventof a power failure, escape sign lumi-naires show the way safely. Together

with junction boxes, distribution boxesand switches, the Cooper Crouse-Hinds GmbH has a complete range

of installation technology products foruse in areas with potentially explosivedust atmospheres.


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Safety through quality

Quality assurance procedure

for apparatus dust explosionprotectionAs with apparatus for use in areaswith potentially explosive gas atmos-

pheres, electrical apparatus for usein areas with potentially explosivedust atmospheres is subject to a

comprehensive system of qualityassurance measures.

All electrical apparatus for use in

potentially explosive dust atmos-pheres has to be submitted to aconformity assessment procedure.

Zones 20 and 21: Apparatus with

EC-Type-Examination-Certificates.Apparatus for use in potentiallyexplosive dust atmospheres in Zones20 and 21 (categories 1D and 2D)

has to be tested by an notified bodywith regard to the explosion protec-tion to determine if they are suited

for use in these areas. With theissue of the EC-Type ExaminationCertificate, the testing authority

confirms this suitability and grantsapproval. The details relating to the

explosion protection in the operatinginstructions are also included in this

test.

Stringent test criteria for

computer-supported testing

of light fittings to guarantee the quality

of products supplied

Zone 22: Stringent production

controlElectrical apparatus for use in poten-tially explosive dust atmospheres inZone 22 (category 3D) is also subjectto a stringent internal production

control to ensure the constant highquality of the products. Moreover, thetechnical documentation confirming

the compliance of the apparatus withthe directive is included in this control.And as safety and quality are always

given top priority at Cooper Crouse-Hinds GmbH, Zone 22 apparatus is

also submitted to a type examinationby a testing authority and the

compliance of the test results withthe requirements of the directive isconfirmed in a Conformity State-

ment issued by the testing authority.After all, sometimes it is necessary todo more than the legislator requires.

CE symbolThe drawing up of a declarationof conformity with the CE symbol

affixed is the basic requirement forthe marketing of a product in theEC area, because with this themanufacturer of a product confirms

that the design conforms to thedirectives and that all the qualityassurance measures have been

fulfilled. It goes without sayingthat all the CEAG brand productshave this symbol, after all Cooper

Crouse-Hinds GmbH is a leadingmanufacturer of explosion-protected

products and, as such, it operatesa quality assurance system in

compliance with the directives.

CE symbol

This starts with the manufacturerhimself, as the prerequisite for themanufacture of explosion-protected

products is an approved qualityassurance system that has beencertified by an independent testing

authority. This confirms that themanufacturer operates a quality

assurance system with documen-tation and regular supervision

(ATEX audit) by an independenttesting authority. The control criteriaapplied here by far exceed those

of the general ISO certification(to ISO 9001, Version 2000).


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Dust Explosion Protection under European Law

ATEXDirective 1992/92/EC of the EuropeanParliament and Council dated 16December 1999 (also known as ATEX

137 or ATEX 118a) defines the uni-form minimum regulations for bothgas and dust explosion protection

within the European community forthe improvement of the health andsafety protection of workers thatcould be at risk due to a potentially

explosive atmosphere.

Within the scope of his duties

according to Article 8 of Directive1999/92/EC, the operator of an

installation has to ensure that anexplosion protection document isissued and is kept up to date.Among other things, this explosion

protection document shall showthe following:

That the explosion risk has beendetermined and assessed

That technical and organisationalmeasures have been taken to fulfil

the safety goals of the directive That the workplace and the wor-

king materials, including warningdevices, are designed, operatedand service safely

The zone classification for thehazardous areas

Directive 1999/92/EC stipulates

criteria relating to the choice ofexplosion-protected apparatus that

are obligatory for the operator.

Thus, unless stipulated otherwise inthe explosion protection document, in

future only apparatus that is classifiedExample: Type label according to new directive 94/9/EG

eLLK 92036/36

S. Nr.: D123456 2000

PTB 96 ATEX 2144

II 2 G EEx ed IIC T4

II 2 D T80C IP66

w w w . c e a g . d e

0102


the respective national rules and regu-lations shall be observed here. It

should be noted that, dependingupon the respective situation, varioustime limits and deadlines can apply.

This also applies to the introduction ofthe new three-zone classification of

110-254 V 50-60 Hz

110-230 V DC

Ta 50 C

Lampe: G13-81-IEC-1305-2

in a given apparatus group and appa-

ratus category in accordance withDirective 94/9/EC (ATEX 95 or 100a)may be used in potentially explosivedust atmospheres. These are selec-

ted according to the different zonesfor potentially explosive dust atmos-pheres (see table).

Directive 1999/1992/EC sets timelimits and deadlines for the introduc-

tion of the minimum requirements forworking materials and workplacesfor new installations and for the

adaptation of existing installationsin which potentially explosive atmos-pheres can occur. As, in this case,changes are permitted during the

conversion of the directive into thenational laws of the member states,

potentially explosive dust atmospheresinto Zone 20, Zone 21 and Zone 22.

It goes without saying that CEAGbrand products conform to the valid

ATEX directive for use in potentiallyexplosive dust atmospheres.

Combustible dusts in potentially explosive atmospheres

Probability of the Classification of Required marking of

occurence of an potentially explosive apparatus to be used acc. to

explosive dust/ atmospheres CENELEC

air mixture acc. to CENELEC/IEC Apparatus Apparatusdirective 1999/92/EC

category category

Are present constantly, for Zone 20 II 1 D

long periods or frequently

Occur accasionally Zone 21 II 2 D

Occurrence due to stirred-up Zone 22 II 3 D

dust not probable, but if they

occur, then only rarely or for

short periods


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All you need for explosion protection

from one source

Explosion-protected

Fluorescent light fittings

Floodlights

Portable lamps

Plugs and sockets

Switchgear

Terminal boxes

Intrinsically safe signal conditioning

eXLinkMalux Finland Oy, P.O.Box 69, FIN-06151 PORVOO, FinlandPhone: +358 (0)19 57 45 700, Fax: +358 (0)19 57 45 750, www.malux.fi

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