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SELECTION OF EXPLOSION PROOF ELECTRICAL EQUIPMENT FOR INSTALLATION IN HARZARDOUS AREA | Cable | International Electrotechnical Commission
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SELECTION OF EXPLOSION PROOF ELECTRICAL EQUIPMENT FOR INSTALLATION IN HAZARDOUS AREAS
Karel Neleman BARTEC NEDERLAND b.v. Keurmeesterstraat 17 NL 2984 BA RIDDERKERK The Netherlands
Abstract – The ATEX directive 94/9/EC was assumed to be a clear ‘New Approach’ directive. Installers and endusers obtain explosion proof required components through wholesalers and build their required solution together without having a notice of the rules belonging to the mandatory directive. Differences between component certification with “U” certificate and complete certification both as EC-type examination certificate will be explained and help to avoid troubles for end customers handling their Explosion Protection Document. Further, a contradiction appears, between the productstandard for flameproof enclosures EN 50018 (EN-IEC 60079-1) and the installation-standard for electrical installations in hazardous areas EN-IEC 60079-14, where direct cable entries in flameproof enclosures are selected. Last but not least a guide through the jungle of many new variations of Ex markings due to harmonisation of IEC standards within the standardization committees. After harmonizing the CENELEC standards for the European (ATEX) market we are nowadays on the beginning of an international harmonisation within the IEC (not only for IEC Ex Scheme, also for ATEX). Index Terms — component certificate, equipment certificate, contradiction, direct cable entries, flameproof enclosures, global standardization, marking jungle, Equipment Protection Levels Due to parallel voting in the national and international committees for EN and IEC standards we see a lot of new markings being created with additional special conditions for safe use.
EC-TYPE EXAMINATION CERTIFICATE VERSUS CERTIFICATE OF CONFORMITY
In the time before ATEX nobody was complaining when companies supplied equipment with component certification. The most important document was the CENELEC certificate; the content of this certificate was often not completely understand by the responsible person of the installation. ATEX is supposed to be a ´new approach´ directive where manufactures have more responsibility for the safety of their supplied products (ATEX 95) and installers and end-users have more responsibility for the installation and application of the products (ATEX 137). “End-user” means plant owner, responsible for the plant (installation) safety. Secondly many installers and end-users are not familiar with the restrictions caused by the installation standard for electrical equipment in hazardous areas. Manufacturers supplying flameproof equipment with direct cable entries through flameproof cable glands are not always aware that for certain applications a barrier gland is required.
In the period before ATEX a different name was used for component- or apparatus-certification, known as Component Certificate and Certificate of Conformity. A Component Certificate needs always additional certification before bringing into service. You could recognize a component certificate through its name and through a ‘U’ behind its certificate number. ‘U’ is German ‘Unvollständig’ and means incomplete certification. Only the component is certified, but not - without further action - suitable for installation in hazardous areas. Not completed component certification has a way of protection- and a group marking. No temperature class is mentioned on this type of certificate. Examples of component certified products are terminals, switchgear, remote I/O. Often additional enclosures are required, however empty enclosures belong also to the examples of component certified products. On the other hand was the Certificate of Conformity which meant a completed certification for the equipment which may be put into service. The only possible limitation could be recognized with a ‘X’ behind the certificate number. It is a marking for attention to the people putting the equipment into service: ‘X’ means ‘special conditions for safe use’, which are written in the Certificate of Conformity. Today, under the mandatory ATEX directive, there is only difference appearing with the marking ‘U‘. Both types of certification, for component and equipment, mandatory for category 1 and 2, are called EC-Type Examination Certificate. Manufacturers certifying their category 3 equipment (not mandatory) receive a Type Examination Certificate. (remark: without ‘EC’). For installers it’s allowed to combine equipment from several manufacturers when each part is completely certified (read: certificate without ‘U’). Each product shall contain a manual and a CE declaration with the delivery. When the manuals are followed, the electrical parameters fit and all EC-type examination certificates are complete certificates this is an allowed situation to put into service. For this reason the cable gland has nowadays a complete certificate in stead of the component certificate before ATEX. In practice working with explosion proof electrical equipment there are many misunderstandings about certification. It seemed that end customers were allowing
2). 1) Example: EEx d control panel with ‘U’ certificate aware about the fact that an overall EEx e enclosure is required. 4: type label on cover of empty enclosure. When this is daily practice. DIRECT CABLE ENTRIES IN FLAMEPROOF ENCLOSURES Fig. 3) Example: EEx de[ia] remote I/O III. the standard mentions flameproof threaded cable entries as a suitable way of installation. containing the complete EC type examination certificate number including a temperature class) This distributor sells empty equipment with complete certification and forces buyers to fill a questionnaire which records what will be build in the enclosure. This is still daily practice. 1 Sometimes there are flameproof enclosures putted into service without any marking at the outside. In the documentation is mentioned that the enclosure shall be EEx e. So. A photograph shall be sent to the distributor to prove the mounted equipment in the housing as evidence for the technical construction dossier. many buyers are Already from the beginning of the CENELEC harmonised standard EN 50018: electrical apparatus for potentially explosive atmospheres . the real ATEX certified workshops can’t compete with regular workshops and the safety is not controlled by a NoBo anymore. but no remark is made that this has to be assembled in an ATEX certified workshop. Is the buyer aware that he buys only component certified products? An empty EEx e enclosure used as junction box needs an additional certification for its application. Asking for the belonging certificate there appears only the EC-type examination certificate (U certificate) for the empty enclosure. An item for the agenda of the ATEX Standing Committee? Fig. 2) Example: EEx e junction boxes Fig. How can the end customer comply this equipment with his area classification? He shall have to check this for his EPD Explosion Protection Document. which means that the distributor may assemble under the responsibility of that manufacturer. where two sealing methods are mentioned: cable entries with elastomeric sealing rings cable entries with setting compound Due to advantages during installation in the field.flameproof enclosures “d”.each type of document containing the word ‘certificate’. The example is a situation like above but. Manufacturers of flameproof cable glands comply with EN 50018 where cable glands can accept only one specific elastomeric sealing ring when dimensioning a minimum axial height of the uncompressed sealing ring of 5 mm. they buy an empty EEx e enclosure from a wholesaler and build their application together. in this case the cable entry shall be marked with an “X”. 2 . So. are aware and guiding their customers through this mandatory certification jungle. component certificates were also accepted. It means in my opinion that the ‘New Approach’ for trading without barriers and controlled safety by Notified Bodies has been damaged. 3) where the modules can be bought through wholesalers. In this case the total heat loss caused by all terminals put into service under their nominal current conditions is taken into account. In some situations it can be that the local distributor of a certain manufacturer has a Quality Control Agreement with this manufacturer. with a distributor not having any workshop at all. It appears that only manufacturers having distributors with ATEX certified workshops in the field. having an ECtype examination certificate for this application and containing to the mandatory appendix of the Production Quality Assurance Notification.1). or with a marking like a component certification. (see Fig. It still happens that machine builders or installers use empty flameproof enclosures to build their control panels. the cable entry with sealing ring is most popular. 4 Even in this example there are mistakes in applying the rules of the directive. 4) Example: EEx d panels with complete certificate Fig. Annex C of this standard describes the additional requirements for flameproof cable entries. 2 Everybody is able to buy empty EEx e enclosures and terminals through wholesalers (see Fig. that means without temperature class (see Fig. 3 Just like example 2 there are many manufacturers of explosion proof remote I/O systems (see Fig. an Epsilon-x in the six angle and a stamp with signature.
4. based on earlier IEC 79-14. the minimum axial height is 20 mm for cable diameter < 20mm and 25 mm for cable diameter > 20mm. The only way out for not necessarily using compound (it is not an easy way of installing in the field) is: . “installation requirements for electrical apparatus with type of protection “d”. Using an Ex II 2G EEx d IIC marked cable gland in an Ex II 2G EEx d IIC T6 marked enclosure (see Fig. 7 Many cable types comply with above description so. the flameproof enclosures have an internal source of ignition. For example motor switchgear or electronic controllers.4 for the selection of cable entries in flameproof enclosures. are non-hygroscopic. So installers shall have to go for the second option: b) thermoplastic. The special conditions for safe use. This option is only applicable when specific cable has been certified by a Notified Body in combination with the cable entry device (read: cable gland) and as a part of the apparatus where applied on. if any. the installer has to comply with the installation standard EN 60079-14: this standard is a European harmonised international standard.” First contradiction occurs checking only the marking according to ATEX. In EN 60079-14 are in chapter 10 the additional requirements for type of protection “d” – flameproof enclosures mentioned. Fig. First question to be answered is “does this enclosure contain an internal source of ignition?” Well. not be okay at all.4.gas of group IIB and area classification is Zone 1 and 3 the volume of the enclosure is smaller than 2 dm .4. may utilize flameproof cable entry devices. belonging to 10. in some situations a flameproof enclosure is used as a junction box only. flameproof enclosures. describe the limitation denoted by the X after the certificate number: “the cable glands shall not be used with Group IIC flameproof enclosures that 3 have a volume that exceeds 2000 cm . For an installer often buying cable in a stadium of the project where the apparatus already is available. where only for IIC enclosures with a volume greater than 2 litres barrier glands or sealing rings with higher axial heights are required. Its earliest basis for the chapter we’re now talking about is BS 5345: part 3. marked with an ATEX certificate number extended with the “X”. the right fitting cable entry devices have to be selected by going through the selection chart in figure 7. Where explosion proof electrical apparatus have to be installed. but it doesn’t have to be explained that in most applications where type of protection “d“ apply. has extruded bedding and the fillers. Following the flowchart the second question is “does the hazardous gas require IIC apparatus?” Answering this question with “yes” means a loud and clear contradiction with the product standard. Specific is sub clause 10. This made it practically only suitable for manufacturers of apparatus with mounted cable tails and cable glands as cable entry devices (see Fig. so this may be considered as no internal source of ignition. Most manufacturers of flameproof cable glands maintain only 5 mm axial height. 5 Second contradiction appears where not only the product standard EN 50018 has to be complied with.However for flameproof enclosures of Group IIC with a 3 volume greater than 2 dm . b). thermosetting or elastomeric cable which is substantially compact and circular. Group IIC) but can be due to the marked X behind the certificate number of the gland. 6). The standard is pointing to 10. this method is practically not applicable. 5) seems to be okay (both category 2G.4. Fig. 10. This means when installer follows 10. Fig. incorporating a sealing ring selected in accordance with figure 7.2.gas of group IIB and area classification is Zone 2 òr .2 he can choose from 6 options as suitable way of direct entering a flameproof enclosure with a cable. these glands are often certified Ex II 2GD EEx d IIC.2: “The cable entry system shall comply with one of the following:” a) cable entry device in compliance with IEC 60079-1 and certified as part of the apparatus when tested with a sample of the particular type of cable. d) or e) which means compound sealing devices like a stopping box or sealing chamber or even better certified flameproof line bushings with compound filling around the individual cores. terminals are under normal operation not sparking.2. 6 3 .
f) other means which maintain the integrity of the flameproof enclosure. Manufacturers for heating equipment take care for the right belonging installation material. 12). 11). 4 . Sealing devices shall be fitted at the point of entry of cables to the apparatus. the real safety depends on the quality of the installers work. 8). While connecting equipment for electrical heaters can be made with type of protection “e” .increased safety. These stopping boxes and barrier glands are certified as equipment and therefore suitable for mounting by installers. d) flameproof sealing device (for example a stopping box or sealing chamber) specified in the apparatus documentation or having a component approval and employing cable entry devices appropriate to the cables used. 9) with compound between the individual wires. e) flameproof cable entry devices incorporating compound filled seals around the individual cores or other equivalent sealing arrangements. This last option is an opportunity to use by Notified Bodies for special occasions. Although the installer has to fulfil the safety instructions in the installation manual. So. like those which are used in flameproof conduit systems (see Fig. line bushings with individual cores for connecting a junction box to a flameproof enclosure to made indirect cable entry (see Fig.In many applications the enclosure contain switchgear and terminals. Fig. 11 This fifth option means the application of factory made cable entries with compound resin filled bushings (see Fig. 9 This option means the application of stopping boxes. 8 What other options remain? c) mineral-insulated cable with or without plastic outer covering with appropriate flameproof cable entry device. practically the only way out is a group IIA / IIB in combination with area classification Zone 2. or filling chambers in so called `barrier glands´ (see Fig. Most applications exceed 3 the 2 dm (see Fig. The sealing devices such as stopping boxes or sealing chambers shall incorporate compound or other appropriate seals which permit stopping around the individual cores. It’s a type of cable appearing in heating technology. 10). Fig. Here is the explosion safety guaranteed. 10 Fig. Mineral insulated cables are not often used by general installers. not fitting under a) to e) Cable glands having a elastomeric sealing ring device obtaining a 20 mm axial height can reach the right flame path over the jacket of the cable but not the additional requirements for setting compound between the individual cores of the cable! Fig. there is no real need for this type of cable entries in flameproof enclosures.
are suitable for the application of direct cable entry systems. 13) where Ex nA: ‘non arcing’ is for the lower terminal box. Both. marked 2G (read: Zone 1). mean in daily practice? Manufacturers of flameproof electrical equipment want to have the highest possible safety level to obtain the chance to put their equipment in as much as possible applications. Manufacturers which are aware of this contradiction ask the customer already during quotation in which Zone the electrical flameproof equipment will be used. The contradiction is shown by not only the 2G marking on the enclosure but also the 2G marking on the cable gland. In 1996 when ATEX directive 94/9/EC came in to operation. 12 To have guaranteed safety for flameproof enclosures it’s important to be aware that indirect cable entries are from manufacturer completely assembled. Threaded entries. In known situations the manufacturer will apply an additional warning label on the equipment mentioning the application only suitable for Zone 2. the certification for flameproof enclosures is often suitable for category 2G (Zone 1&2) according to directive 94/9/EC. EEx m changes into Ex ma and Ex mb where Ex ma a moulded version suitable for Zone 0 and Ex mb a moulded version applicable for Zone 1. is by the selection of cable glands with elastomeric sealing rings devalued to a Zone 2 application. EEx p & EEx n some changes are to be introduced. 13 Fig. made by the manufacturer. What does clause 10. It is to be expected that Ex nL in IEC 60079-15 moves to IEC 60079-11 intrinsic safety.2. To check which European standard is harmonized under the directive you can check the Official Journal (OJ) at the website of the European Union Online at: http://europa. to mention a sentence in the special conditions for safe use. When such an enclosure is selected for housing electrical switchgear in Zone 2. 5 . From the non incendive variants IEC 60079-15 Ex nC will probably extended with Ex mc as described above and Ex nP shortly exchanged by Ex nZ will change into Ex pz where this last mentioned way of protection for pressurization will be moved from IEC 60079-15 to IEC 60079-2. So. safety level Ex ic for zone 2. Fig. selectable by end customer or installer. Group IIB according to EN-60079-14. the transition from national standards to European CENELEC standards was causing a new recognizable way of marking the equipment by using not only the Epsilon X sign but also the double EE where the first E was to show that the equipment was certified according those European harmonized standards.IV. only for EEx m. EEx p changes into Ex px and Ex py each having a certain level of protection. when CENELEC was founded. The belonging EC type examination certificate describes in such situations for example Ex II 2G EEx d IIB T5. Ex nC: ‘closed construction’ has been used to the electronic and switchgear in the upper box and [pz]: this controller is an associated apparatus necessary for safe operation of the belonging (not shown) purged enclosure. The electrical apparatus. manufacturers and installer are working in the correct way.html Nowadays. but the final solution contains an Ex marking which is not representative for the actual zone 2 (read: 3G) application. it’s possible to use flameproof cable glands with elastomeric sealing rings.int/comm/enterprise/newapproach/standa rdization/harmstds/reflist/atex.” INTERNATIONAL DEVELOPMENTS IN STANDARDIZATION COMMITTEES CAUSING A COMMOTION IN WAY OF MARKING THE EQUIPMENT th In the late seventies of the 20 century.4. to be installed in Zone 1 both having a volume that exceeds 3 2000 cm . EEx nL will change to Ex nL and it is supposed to be changed in future to Ex ic analog to the Ex ia and Ex ib variants for Zone 0 respectively Zone 1. having a marking Ex II 3G Ex nAC [pz] IIC T4 (see Fig. It should be discussed in the ATEX Standing Committee to add in future on EC type examination certificates for direct cable entry systems not fulfilling this rules. For the standards suitable for gas hazardous areas no great changes occur. The cable entries are not part of the certification.eu. Responsibility for this selection remains always at the applicable end customer. the standardization committees are often working in a way of parallel voting for European EN standards and International IEC standards. like: “the cable glands shall not be used with Group IIC enclosures. This causes a renewed use of “single E” for Ex marking. In future an Ex mc variant will occur as extension from EEx nC. As an example is shown a controller for purged cabinet for Zone 2. or Group IIB enclosures. The installation manual of the flameproof apparatus has to mention EN 60079-14 as suitable standard for the selection of a sufficient cable entry device. so not dependent from installers work. many of these European standards where renewed and harmonized under the ATEX directive 94/9/EC.
Safety for dust explosion hazards could be realised by a minimum grade of the IP (Ingress Protection) rate and a limited maximum surface temperature of the equipment. When this same way of explosion protection has been used under the IEC international standards. Ex iaD and Ex ibD are both intrinsic safe ways of protection for Dust. General about IEC Ex Scheme: on this moment 25 countries are member of IECEx. covering the production facility). The ExTR can be used to obtain a national required certification (for example FM for a European manufacturer wanting to sell his products to the USA). mechanical equipment can’t be assessed. The newest IEC 60079-0 Edition 5 which will be launched in 2008 is already as Committee Draft in de Standardization Committees. Ex iaD can be used up to Zone 20. the EN-IEC 61241-1 applies. The cohesion between Categories and Equipment Protection Levels (EPL) can be declared with table I: TABLE I Category M1 M2 1G 2G 3G 1D 2D 3D Zone 0 1 2 20 21 22 Group I I II II II III III III EPL EPL Ma EPL Mb EPL Ga EPL Gb EPL Gc EPL Da EPL Db EPL Dc Remark: preliminary (committee draft) IEC Ex Scheme is coming up which aims one single certificate for any hazardous area product recognized and accepted throughout the world. An example is a mobile computer (see Fig. Practice B calculates with Tmax = Tsmouldering(12. Material group I and II will be extended by material group III I : Mining II : Gases and vapours III : Dusts. where the relation which way of protection is suitable for application in which hazardous area has to be made by the suitable category and not the choice of a certain way of protection. Here will the Categories be replaced by Equipment Protection Levels. tD means ‘protection by enclosure for Dust’ A means ‘practice A’ 21 means ‘suitable for Dust zone 21’ The rest of the marking is identical to the EN way. Comparing to ATEX. only EN 50281-1-1 was a suitable standard to design electrical equipment. fibres and flyers This material group shall identify the most important differences between the several kinds of dusts: IIIA : combustible fibres & flyers (parts with diameter > 0. the procedures are as follows: An ExCB (Certification Body) issues an ExTR (Test Report. Ex ibD up to Zone 21. however Practice A calculates like the EN standard with Tmax = 2/3 x Tignition and Tmax = Tsmouldering(5mm) – 75°C where the lowest temperature will be the maximum allowable surface temperature. there have been several changes due to the harmonization of international standards as follows: for European harmonized standardization of electrical equipment. Currently only electrical equipment to IEC standards are applicable with IEC Ex Scheme. 13) where also the marking Ex II 3D Ex tD A22 [pD] T80°C applies. Practices A and B are both obtaining a same level of protection. This same introduction appears in the latest edition from IEC 60079-14. The Certificates of Conformity are created directly on the IECEx website. 14 6 . where nothing is mentioned about the in Europe mandatory ATEX categories! Due to the fact that IEC is international and EN only European there have to be from both sides concessions in the standardization committee during parallel voting of international and European standards. Marking is for example Ex II 2D IP 65 T80°C.For dust however. The other ways of Dust protection are not dependent from those practices. It was the standard for ‘protection by enclosure’. The way of protection is a choice of the manufacturer of the equipment.5mm) IIIC : combustible conductive dusts Last but not least there will be a change caused by the fact that EN 50014 has already been superseded by IEC 60079-0 Edition 4. With the acceptation of international standards under the ATEX directive several new ways of protection are possible to apply: Ex pD according to IEC 61241-4 is pressurization for Dust where the marking looks like Ex II 3D Ex pD 22 T135°C. where for Zone 2 no Notified Body is required. Practices A and B are only applied for Ex tD. covering the product type) and a QAR (Quality Assessment Report. Also called ‘protection by enclosure’ but using a way of marking for example: Ex II 2D Ex tD A21 T80°C.5mm) – 25°C. A control unit for such a Dust protection can be the same one as above (see Fig. General. Australia accepts certificates in their national law. Remarkable is that for European ATEX selection the marking of the right category is important.5mm) IIIB : combustible dusts (parts with diameter < 0. 14) Further on in the jungle of new markings a new material group will be introduced when IEC 60079-0 fifth edition will be released. IEC Ex Scheme is for Zone 2 requiring a certification with a Certification Body. Fig.
ACKNOWLEDGEMENTS Special thanks to Pete Connell from BARTEC UK who was willing to help me checking my written text in the English language. check the cable entry device in order to the applicable hazardous area zone and gas group. 5.and installation standards. It’s important that everybody recognize the difference between component. IECEx is possible the final goal for global harmonization in one big global market. IEC Ex Information. VITA ing. installers and end users need to be up to date how to deal with electrical equipment which have to be installed in hazardous areas.bartec.Part 15: Construction. www.0 (31/580/CD Committee Draft). The application of equipment which have to be certified in the right way is a basic requirement for your final EPD. EN 61241-1: 2004. Electrical apparatus for potentially explosive atmospheres . REFERENCES Since many standards have changed and still are changing. due to unknown contradiction of product. Since 1990 he is working for BARTEC where he started as sales engineer for explosion proof electrical equipment.fully visible for the whole world to read and check the status. He started an international successful control panel and switchgear building division with an ATEX Production Quality Assessment Notification within BARTEC.Part 2: Pressurized enclosures "p". You’ll have to check www. Electrical apparatus for use in the presence of combustible dust Part 4: Type of protection “pD”.com European Union online. Electrical installations in hazardous areas (other than mines). Karel Neleman (B Eng) graduated as Bachelor of electrical. Equipment intended for use in potentially Explosive Atmospheres (ATEX).com on a regular basis to keep informed. Today he is Business Development Manager for explosion proof Automation Technology. Electrical apparatus for explosive gas atmospheres . EN 60079-15: 2005. Ed. EN 61241-11: 2005. Where ever flameproof enclosures are to be installed or maintained. EN 60079-2: 2004. Electrical apparatus for explosive gas atmospheres . Many end users have not the right cable entry devices on their installed equipment. Electrical apparatus for use in the presence of combustible dust Part 11: Protection by intrinsic safety “iD”.nl IX. test and marking of type protection "n" electrical apparatus.iecex. A new certification scheme comes up.Flameproof enclosure "d". Electrical apparatus for explosive atmospheres . see URL link at www. Electrical apparatus for use in the presence of combustible dust Part 1: Protection by enclosures "tD". IEC 60079-0. the Netherlands who keep each other informed in the latest developments of the standards for explosion proof equipment suitable for installation in hazardous areas. NOMENCLATURE ATEX Atmospheres Explosible (French) CE Conformité Européenne (French) CENELEC European Committee for Electrotechnical Standardization EC European Community EEx d way of protection: flameproof enclosure EEx e way of protection: increased safety EEx i way of protection: intrinsic safety EEx m way of protection: moulded ecapsulation EEx n way of protection: non incendive EEx p way of protection: pressurized EN European Norm EPD Explosion Protection Document EPL Equipment Protection Level ExCB Certification Body authorised IEC Ex Ex iD way of protection: intrinsic safety for Dust Ex mD way of protection: moulded for Dust Ex pD way of protection: pressurized for Dust Ex tD way of protection: protection by enclosure ExTR Test Report according IEC Ex Scheme IEC International Electrotechnical Commission NoBo Testinstitute authorised by EC OJ Official Journal (European Commission) QAR Quality Assessment Report U incomplete component certificate X certificate with conditions for safe use Directive 94/9/EC.Part 0: General requirements. CONCLUSION [1] [2] [3] VIII. Also a word of thanks to all members of the NEC 31 in 7 . VII.and installation standard. Finally be aware that markings on explosion proof electrical equipment are changing due to international harmonization of product. Electrical apparatus for explosive gas atmospheres. He is member of the Dutch standardization committee NEC 31 and ATEX authorised contact. EN 60079-14:2003. EN 61241-4: 2001.iecex. EN 50018: 2000. [4] [5] [6] [7] [8] [9] [10] [11] VI.and equipment certificate. V.and electronic engineering (information technology) at the University of Professional Education Rotterdam in 1989.
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