ATEX termoventilmecstandard for industrial suction plants - ENG

26 XYLON INTERNATIONAL July-August 2006

TECHNOLOGY

Starting from July 1, 2006, in fact, the Atexstandard will become fully effective: it dealswith all the risks related with explosions, anytype, that may occur within a working envi-ronment. It might not sound very interestingfor our industry, wood is not very explosiveafter all... but reality is much different. In thepast three years, when it came to the pur-chase of a new plant or machine, everywoodworking sector, from the production ofparticleboard panels, furniture and plywoodto window manufacturers, small or largehandicrafts companies processing woodand its derivates had to face the Atex stan-dards. As a matter of fact, we cannot deny

that, whatever process must be carried out,hazardous materials are produced or used,for instance wood dust, or some productsused during the finishing stage, which in aclosed environment may create a potential-ly explosive mix with air. By July of this year,the compliance will have to be completedalso on old production plants and lines. Except particular cases, the working envi-ronment in woodworking companies is notATEX-classified because the dust concen-tration in the air - even reaching 5 mg/m3,which is considered as the maximumaccepted, or better tolerated limit forhygienic reasons - would be well below thevalue of explosion risk.Standard cleaning procedures combinedwith chip and dust suction plants - whichare currently compulsory on each machine -allow to consider these risks as inexistent.It is useful to point out that nowhere around

ARE YOU REALLY READY FOR THE ATEX STANDARD?Some tips, explanations and comments to employers and safety managers about the compliance of the existing plants in the woodworking industry to prevent the unpleasant consequences, also penal, listed in the standard.

ATEX directive and test laboratories

Given the several applicationsreceived, UNI decided to repeat thecourse "ATEX - 1999/92/EC Directive -Plants in environments with explosionrisks”, which was held on March 30 inMilan, and the course “General require-ments for the compliance of test andcalibration laboratories. UNI CEI ENISO/IEC 17025:2005 standard” washeld in Milan on April 27 and 28, 2006.

Effects of the explosion of non-ATEX sleeve filters.

Xylon Int - da 026 a 031 14-07-2006 16:06 Pagina 26

the world an explosion has ever occurredinside a woodworking company in themachining area, even though in the past (andalso today in certain geographical areas)hygienic conditions were extremely different,with the presence of dust accumulation andthe frequent absence of suction plants.For processing machines and lines, theAtex issue is not considered as significantand, in fact, in more than thirty Europeanstandards (most of them harmonizedaccording to the Machinery Directive) refer-ring to an equal number of machine types,

the risk of explosion has always beenexcluded, unlike the fire risk.The situation is utterly different for suctionplants and in particular closed sleeve fil-ters, storage bins, dust collection bins,cyclones, suction units, etc., where the riskof explosion in a potentially explosiveatmosphere not only exists, but the numberof accidents recorded, even serious,requires utmost attention by manufacturersas well as by users in the purchase phase.Though in general, the environment is notclassified and machines and plants mustnot be marked ATEX, to obtain the EC mark-ing manufacturers must evaluate all existing

July-August 2006 XYLON INTERNATIONAL 27

risks, and in particular the RES 1.5.7 ofAnnex I to the Machinery Directive and, asrelates to suction systems, they also have toconsider that the requirements of the spe-cific directive 94/9/EC are applicable andprevailing.The 94/9/EC directive develops the men-tioned concepts by giving a detailed defini-tion of “explosive atmosphere” (see tableon page 30) and setting the limits of appli-cation possibilities to ensure maximumsafety for the machine itself. The same goes even when the working envi-

Protection systems

These are devices whose function is to block explosions and/or restrict theaffected area, which are separately marketed as systems with independentoperation (not a component). Safety and control systems installed outsidethe classified zones are included only when they contribute or are request-ed for the correct operation according to the risk of explosion. They do nothave to bear the EC marking as long as they can be considered as an inte-gral part of the device.Examples:• Spark detection and extinguishing systems;• explosion relief systems (explosion-proof devices); extinguishing curtains.

Effects of the explosion on an ATEX-compliant filter.

ronment is not at risk of explosion, but insidethe machine users process materials thatcreate a potentially explosive atmosphere. Summing up, users must comply with twoDirectives: one is addressed to employersand deals with safety in working environ-ments (99/92/EC) where they have to identi-fy and declare the potentially hazardousenvironments for explosions and the corre-sponding level of hazard; the other (94/9/EC)requires the construction of machines withno ignition sources in case they are locatedin explosive atmospheres or where potential-ly explosive materials are processed. It is therefore up to machine and plant usersto classify the different zones of the workingenvironments according to the related risks inapplication of the corresponding directive.Such information, which in case mustinclude precise indications about the exactplace where the machine will be installed,must be handed over during the purchase of



TECHNOLOGY

machines to technology suppliers, who willthen provide the EC marking accordingly. If the area is classified at risk of explosion,machines (but also all equipment, electricor not, located in that environment) will haveto be provided with ATEX marking, in addi-tion to the usual EC marking.If, like in most cases, the area is not classi-fied, yet there is a risk of an explosive atmos-phere in closed containers, such as in thecomponents of air intake systems, it is up tothe plant manufacturer to evaluate the risksof potential explosion generated by the sys-tem and the necessary corrective actions toreduce or eliminate them. In case suchactions are not enough and there is still a‘residual’ risk, it is necessary to adopt pas-sive or active safety systems according tothe evaluated residual risk of explosion. The manufacturer, or the person providingthe market with complete plants ormachines used in potentially explosiveatmospheres, will consider that:- the air-wood dust mix is potentially explo-sive in a closed environment;- the explosion features of the mix dependon multiple physical variables of theprocessed product and, after sample analy-sis, they are evident through Kst values(pressure increase in the explosion time unit)

and Pmax values (maximum pressure valuethat can be achieved by the explosion);- the obligation to specify in the manuals thesuitability and application limits of theirmachines, which may contain potentiallyexplosive atmospheres; - the obligation to provide machines with allactive or passive safety and protection sys-tems - following to risk analysis - which mustbe certified by an authorized organizationon behalf of the manufacturer; - the obligation to specify in manuals theresidual risks of the machine whenever it isused in complex systems and/or plants;- for complex systems or plants, the design-ers or distributors must execute a newanalysis of the system’s risks, carefully eval-uating the residual risks of each machineof the system-plant, and applying or sug-gesting the application of further safety andprotection devices which are certified orfrom certified divisions.- they must be able to prove the existence ofall the documents related to the analysis ofrisks and calculations that have deter-mined the choice of the different protectionand safety systems and their number (forinstance: number of certified passive pro-tection diaphragms and calculation of therelief areas).

Effects of the explosion inside

a non-ATEX centrifugal fan.

Centrifugal fans designed

to withstand 0.5 bar overpressure.


July-August 2006 XYLON INTERNATIONAL 29

The manufacturers’ obligations are there-fore rather heavy and they do not dependonly on the classification of the areas wherethe machine or plant will be placed.Once the compliant plant or machine isinstalled, the supplier will hand over an ECcertification where also explosion risks areconsidered. But this is not enough for thepurchaser to feel 'at ease' and with noresponsibility, most of all if the non-compli-ant elements are evident.Unfortunately, there are suppliers who mar-ket non-compliant products and have noscruples in certifying them with an EC-mark.Whether they are panel, furniture manufac-turers, joiners or other, final customers arereassured, yet they are not aware they haveinstalled a non-compliant plant and they arealso responsible for it.In some cases we also see an illegal atti-tude where users of such plants are per-fectly aware that a highly profitable pricehides a false EC marking by the supplierand, despite that, they knowingly prefer to

save money and neglect the law obliga-tions, pretending that...They do not consider that, if a non-compli-ant plant, yet EC marked by the supplier,should occasionally cause an accident orexplosion damaging people or objects, theresponsibility is not only of those who have

Classification of zones

Categories Protection level Zone gas, mist, vapor Zone dustCategory 1 (certification) Very high 0 20Category 2 (certification) high 1 21Category 3 (certification) normal 2 22

Values for equipment not used in mines.

ATEX-compliant dust

and sawdust storage bin.

ATEX marking

Table with diagram (see drawing):ATEX marking (additional to EC) when the machine operates in potentiallyexplosive environments.

EC: EC markingxxxx: identification code of the Notified Institute (when necessary)Ex: Additional Ex markingII 3: Equipment group and protection categoryG/D: Gas/DustIP55 T125°C: IP and maximum surface temperature developed

CE xxxx Ex I I 3 D IP55 T125°C



TECHNOLOGY

light-heartedly, in good or bad faith, sup-plied the plant certification, but also, if aninjudicious purchase should be proved, ofthe owner and user. In fact, it not enough tohave a compliance certificate before evi-dent law violations or faulty supplies. Theresponsibility is also penal and in this caseit also affects the legal representative of theuser company or the safety manager.So, on one hand, more attention is requiredby purchasers during the acquisition of newplants, on the other hand, it is important thatplant suppliers are able to fully comply withstandards. Purchasers must always makesure that their supplier has carried out thenecessary calculations, tests and evalua-tions. With the introduction of the Atex stan-dards in 2003, in fact, technology manufac-turers had to revise and adapt their prod-ucts through studies and research to evalu-ate the resistance of structures, closed con-tainers, risks of explosion and propagationby simulating the explosion inside themachines they manufacture, to see theirelastic and plastic deformation, resistancelimits till destruction; accordingly, they haveadopted and installed a series of active andpassive safety devices (see box on page 27)which, in case of accidents, minimize thedamages to people and objects and preventthe explosion propagation to nearby

machines and environments. As you can see,the compliance of woodworking plants withthe Atex directives is neither easy nor imme-diate, and it requires a correct evaluation ofthe operations to carry out, quality of actionsand persons in charge. In fact, it is funda-mental to apply to skilled suppliers who havealready carried out a careful analysis of theirproduction, checking and comparing it withthe requirements of the standard, and whoare able to guide furniture, panel, window andproduct companies by protecting themagainst possible future risks.With this article we hope we can increasethe awareness of the parties involved, usersand suppliers of machines and plants, con-sidering that three years after the introduc-tion of the standard on a European scale,this standard is often totally unapplied! We

Atex compliant dust

and sawdust storage bin.

Atex compliant

passive safety screen.

Definition of ExplosiveAtmosphere

• presence of gas, vapor, mist, dust• mixture with air• between 0.8 and 1.1 bar• between -20 and +60° C• risk of potential propagation

hope to make things clearer, so that manyfalse beliefs and commonplaces are ques-tioned, such as the widely spread beliefthat: “you only need certified passive pro-tection diaphragms in a closed sleeve filteror in a storage bin to comply with Atex”.Well, that’s wrong! The pictures and tables in this article are acourtesy of the Research and Study office ofTVM termoventilmec SpA (www.tvm-ter-moventilmec.com) based in Spresiano(Italy), a company that designs, manufac-tures and installs industrial suction, filteringand purification plants, pneumatic transportplants, storage bins, fans, sleeve filters,safety devices, etc. During the latestXylexpo in Milan, in May, TVM presented anoperating air suction plant in compliancewith the current safety standards.

by Danilo Morigi


ATEX termoventilmecstandard for industrial suction plants - ENG

Technology

Transcript of ATEX termoventilmecstandard for industrial suction plants - ENG