2rlp Posted June 6, 2012 Report Share Posted June 6, 2012 Hi, I have to enclose a V130 33 TRA22 & a 24 V SMPS unit in an Explosion Proof Enclosure. What are the precautions that I have to take? Should I use Zener barriers? If so should I use them only for DIs & DOs, or also for the Analog I/ps & O/ps? Pl help me on this issue Thanks Ron Quote Link to comment Share on other sites More sharing options...
Walkerok Posted June 6, 2012 Report Share Posted June 6, 2012 Im sorry but I don't think your question can be answered simply. First of all what zone classification are you actually in? Class ? Div ?. Exploxion proof would indicate that there is a NEMA 7 or 9 or both cast aluminum enclosure involved. This would also indicate that the V130 is completly inside the enclosure and that you can not actually touch the V130 unless the enclosure is open. NEC has requirements about how all of these types of connection need to be done, but it is much more of an art foem and not a science. You get 20 people in a room and your lucky if 2 agree with each other on the exact requirement for all aspects of the installation. Generally if everything is in an actual Xp enclosure you just have to seal the entry and exits correctly to maintain the XP status of everything in the enclosure. The V130 is in no way ok to expose to the explosion causing atmosphere. If you are not really explosion proof and are actually a Class 1 Div 2 environment then if the V130 is exposed the only choice you have is to purge the cabinet with conpressed air using either a Z or Y purging system (depends on the actual zone) which allows items in a C1D2 zone to be treated as if they are installed in an unclassified zone. Sorry but this is much more involved than can actually be answered here completely. Keith Quote Link to comment Share on other sites More sharing options...
MVP 2014 Simon Posted June 6, 2012 MVP 2014 Report Share Posted June 6, 2012 I would get involved directly with someone who has qualifications in the field of hazardous areas. Firstly you want to be sure the design is going to be safe. Secondly you want to be sure no-one is going to blame your equipment if there is an incident. Quote Link to comment Share on other sites More sharing options...
2rlp Posted June 7, 2012 Author Report Share Posted June 7, 2012 Hi Simon, Thanks for your reply. The requirement is for ATEX Intrinsic Safety. I have not done anything like this before. Have only made straight forward panels for the indoor class. Any further insight would be welcome Ron Quote Link to comment Share on other sites More sharing options...
sgull Posted June 7, 2012 Report Share Posted June 7, 2012 Hi Ron I think you need to look at the complete installation. 1. If the instruments are in the ATEX area then they need to be intrinsically safe (IS) instruments and you will need barriers on all analog in/out and DI,DO. (some switches can be classified as "simple devices and do not require barriers but you would need to used extra low voltage) 2. If the instruments are in a safe area and the PLC is in the atex area, then the PLC needs to be in an explosion proof enclosure and you do not need barriers. 3. If both are in the same area you need an explosion proff enclosure and barriers as per 1 above. Since the HMI is useless when enclosed in an enclosure, you may need to use remote I/O in the enclosure and move the HMI to a safe area. (this you can do without a barrier). There are probably several more issues when you look at this in more detail any you should consult an expert who can visit and survey the site for you. Regards Denis Quote Link to comment Share on other sites More sharing options...
MVP 2014 Simon Posted June 7, 2012 MVP 2014 Report Share Posted June 7, 2012 Hi Ron, Based on my knowledge of the topic, I agree with Denis regarding the general configuration. However you are potentially left exposed to liability if you don't consult a qualified Hazardous Area specialist. The extent of this depends on the legal situation in your country. You could be prosecuted just for installing something without proper certification. If there was an incident, then they can really throw the book at you, even if your equipment did not cause the problem. Being able to say you discussed the issue on the Unitronics forum is far from an adequate defence. There are no doubt many installations out there that don't comply with standards, but are technically safe, and probably many that are not safe. The fact that these haven't casued an explosion (yet) is not a reason to disregard due caution. The first thing you need is the hazardous area classification. At the very least this needs to be done by a trained person, preferrably paid for directly by the end-user (either a direct employee with the relevant qualifications or a paid consultant). I hope this doesn't come across as overly alarmist, and at the end of the day, this has very little to do with me. However the photos I have seen of sites that have been levelled by exposions speak for themselves. The consequences are rare, but catastrophic. If I was in your position I would take all possible steps to get it right and also be able to prove that I took these steps. Quote Link to comment Share on other sites More sharing options...
2rlp Posted June 8, 2012 Author Report Share Posted June 8, 2012 Hi, Thank you both sgull & Simon. I have decided to take your advice & have asked for more clarifications from the concerned party. Hope they provide me with the right answers. This will help me decide if I would want to go ahead with the project. Ron Quote Link to comment Share on other sites More sharing options...
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