I'm wondering what is involved in modifying equipment that has been certified for use in explosive atmospheres, such as ATEX Zone 1 or 2.

A couple of times recently at my work we have discussed integrating some technology into a processing facility with explosive atmospheres, but the certified equipment available COTS does not quite meet the specification we need.

Rather than develop a whole new product from scratch, I'm interested in knowing whether a company can take another company's product, swap out one part (in our case typically passive parts like the lens in a security camera or the lid of a junction box) for a part that we design, and have either our part or the combination of our part and the original equipment recertified.

  • \$\begingroup\$ I guess it's more electrical design rather than electronics? In my understanding it would be the typically be the responsibility of an electrical engineer to do this work which is why I felt like this was an appropriate forum. I just assumed there would be electrical engineers who design Ex-rated electrical devices here that might help. There are also lots of other questions about certifications and regulatory standards already answered here \$\endgroup\$ – Rorxor Mar 27 at 4:40
  • \$\begingroup\$ I may be incorrect, but typically my experience has been that questions about whether doing X or building Y meets a given standard or certification are borderline (for the same reasons that legal advice is difficult to offer). \$\endgroup\$ – JYelton Mar 27 at 5:21
  • \$\begingroup\$ Searching the EE Stack for the term "certification" yielded 772 results, and most of the results that I looked at were from people asking similar questions and they were answered without any issue.I get your point about legal advice, but really for something like this, anyone who has worked with the necessary ISO standard could just reference the relevant section from it directly without implicating themselves. \$\endgroup\$ – Rorxor Mar 27 at 5:34
  • \$\begingroup\$ I've retracted my close vote. Good luck. \$\endgroup\$ – JYelton Mar 27 at 5:58
  • \$\begingroup\$ I appreciate it JYelton, thanks for the consideration! \$\endgroup\$ – Rorxor Mar 27 at 6:21

In our company we develop products for zone 1 and 2. The functional aspect does not change much compared to the conventional design, however, safety and robustness play a big role here and so does the selection of components.

There are probably companies out there, which could take up the challenge to make your device meet zone 1 and/or zone 2 requirements. They would have to be specialized in such field, because it involves meeting several complex requirements, and usually a standards expert is among the main characters in the designing loop.

Due to the stringent component selection, it is often not feasible to reuse an old design. What is done some times, is to buy small modules as black-boxes which have already been certified for zone 1 and/or zone 2 (saves time and money). If that is not possible, as it is the case with passive elements, it is up to the designer and standard expert to determine what are the implications of using such components in case of failure. Sometimes it can get a bit more complicated, if you have other companies producing a part for your design, for example a transformer. If it is not a client specific design, they also would have to change their design to meet your needs.

Below are a few examples of implications or aspects which should be considered while designing such electronics:

  1. Galvanic Isolated Power Supply: failing to regulate and monitor the output voltage / current, can lead to a unpredictable behavior, which in turn can expose energized pins to a explosive atmoshpere.
  2. Limited capacitance: Maximum stored energy in the device must be limited
  3. Fuse selection is much stringent due to lower and upper limits
  4. Temperature monitoring of the critical (if not all) components is sometimes a must

As described here, there are different types of certifications and approaches to certify your product. I believe, the best approach would be:

  1. Have your requirements predefined (where to use the device, at what conditions and so on)
  2. Have your requirements checked by a standards expert. He will then say what standards and specific requirements will have to be met
  3. Come up with a design and all counter measures.
  4. Even before you start the design, involve a certification body (who is going to certify your product) in the loop, to check whether it is even feasible to have your product certified later. Based on their experience, they might as well give your hints.
  5. Then, and only then, start with your design.

I hope it helps

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