Class 1, Div 2

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I'm working on a project that is likely going to be Class 1, div 2 certified for use in explosive gas environments. The unit has several external interfaces that will need to be conditioned to meet the C1 D2 spec to not generate a spark that could ignite the gas vapors. Basically I'm looking at RS-232, RS-422/485, Ethernet, USB, and some GPIO's that will need to be conditioned. I'm still researching all of this (just starting), but if anyone has any tips/guidelines, implementation details, it would be greatly appreciated.

Writing code is like having sex.... make one little mistake, and you're supporting it for life.

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Maybe this is of help?

I worked at a company that made equipment for hazardous areas like drilling platforms and refineries; I remember the heavy cast iron boxes with 1" thick walls, sometimes only housing a simple switch and few indicators.

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Thanks... the enclosure is not a problem here, that is already rated. The problem is the exposed I/O's. I have the actual spec's I have to meet, am researching ways to meet those requirements. Basically I need to limit the amount of energy that can be sourced from the connector by shorting any two pins of that connector. The idea is to prevent that short from generating a spark that is capable of igniting the flammable gas vapors in the surrounding environment.

Writing code is like having sex.... make one little mistake, and you're supporting it for life.

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Quote:
I'm working on a project that is likely going to be Class 1, div 2 certified for use in explosive gas environments.

So if you stop posting, we'll all know why :D

Regards,
Steve A.

The Board helps those that help themselves.

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lol, well I already have explosive gas issues... but that's another story :P

Writing code is like having sex.... make one little mistake, and you're supporting it for life.

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As far as I can remember, no connectors where used at all, everything was hard wired via cables entering the boxes with big heavy expensive brass cables glands.

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Perhaps in those applications. Ours will have connectors, hence the requirement to meet the specific standard for energy limiting. Hard-wiring is not an option, nor is it practical in this case.

but thanks again!

Writing code is like having sex.... make one little mistake, and you're supporting it for life.

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thanks for the links checking them out now.

[edit] great links, has some plain-English explanations of what is present in the official specs I have. Thanks again!

Writing code is like having sex.... make one little mistake, and you're supporting it for life.

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Glitch you should look for special connectors too, isn´t?

Good luck!

Regards,
Brunomusw

Regards,

Bruno Muswieck

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yes the connectors are specialized, ruggedized-circular hermetic connectors.

Writing code is like having sex.... make one little mistake, and you're supporting it for life.

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glitch wrote:
lol, well I already have explosive gas issues... but that's another story :P

Do you sit on it?

HM

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Take a look at:

ANSI/ISA 12.12.01

These are requirements for non-incendive and non-arcing circuits for Class 1 Div 2, etc. Your interest might be "non-incendive field wiring" in particular.

Tom Pappano
Tulsa, Oklahoma

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AFAIK, for Ex environment, it is accepted that the voltage must be limited to 8V, to avoid spark issues, so RS232 is not an option for Ex environment. RS485 should be OK, IMHO.

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Maybe you could devise a circuit that disables all power before the connector disengages fully. And no banks of capacitors directly on the power input, only being able to connect them when the connector is fully engaged, with a relay or something.

The Pepperl+Fuchs documents linked to in a previous post seems to apply only to hard wired connections.

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Even with a 8 V limit an RS232 interface is not totally out. Its just that you can't get the usuall voltage levels, but just enough to meet the specs. The Porblem could be that the other devices that someone may connect there must have the limited voltage too.

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I would to see what the produceres of PLC's have that is aproved and then either copy that or if it's small numberes use those PLC IO's inside and the AVR outside.

Jens

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Funnily enough I'm working on a oil tanker in Dubai and all my equipment is hazardous. I'm going on memory here, but I think class 1 div 2 is not quite as stringent as some others. You really need to refer to the standards. I think the PLC I'm using is to that rating and I might guess that you need to ensure surface tmperatures are not exceeded and nothing sparks in normal operation. Again, I'm going from memory as I normally work to euro ATEX requirements - North america is different.

Its one thing to design to meet the specs, its another to have it certified. Expect to spend big money. If the project is small, I'd suggest you buy off the shelf equipment that has the required certification.

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Thanks everyone. My only concern is the electrical side right now, and I think I have it all worked out.

Certification of the full unit needs to be done by the end customer, as they add their own additional boards into the chassis. As such, all I can do is design to meet the spec based on what I have in the enclosure. The cabling, or any external devices are beyond my control, so they are not on my radar either.

Thanks again everyone, got a lot more responses on this than I expected.

RS-232 is not an issue, the spec I'm working against allows for up to 30V. It's all about the energy in this case, and not exceeding the MIE (Minimum Ignition Energy) of the environment we're operating in.

Writing code is like having sex.... make one little mistake, and you're supporting it for life.

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12.12.01 does not seem to prohibit externally ("operator") accessible connectors for nonincendive field wiring. Actions that may be performed by an "operator" (as opposed to a maintenance person following proper procedures) must not cause ignition. If the connector is accessible to an operator it's associated field wiring would have to be non incendive. The graphs actually allow a quite large range of voltages, currents, etc. As one can see, in most cases less with than 12 volts in a resistive circuit you are good to go. If the field wiring may be too inductive or have too much capacitance, you can add resistance inside your equipment.

Testing is not free, but the cost is not all that high. If you are actually going to be shipping a real product, the testing costs will soon be forgotten. You do have quarterly followup inspection service costs, but there again, if you are shipping much product at all, the followup cost is no big deal. I'm currently going through hazardous location testing of some of my components and it is not that hard to meet the requirements for recognition. The main thing is to know from the start what you are going after so that redesigning and retesting can be avoided.

Tom Pappano
Tulsa, Oklahoma

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Thanks Tom. It really is pretty basic, (didn't think it was going to be that simple when I initially asked, but figured it out along the way) But also good to know that I'm probably not missing something somewhere along the way because it was so simple.

Writing code is like having sex.... make one little mistake, and you're supporting it for life.

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I've seen the Class N Div M situation be that the customer's insurance company has different policies on this than do the alliances defining these protection.

So step one is to find out what placates the insurance company.

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Quote:
So step one is to find out what placates the insurance company.

True!

All Glitch needs to do though, is keep his energy below *all* the gas curves, at the worst temps, which is easy enough to do.

Tom Pappano
Tulsa, Oklahoma