Hazardous Location IO control

I'm trying to design a motor control panel (basically pushbuttons and lights with some IO blocks in an enclosure) for use in a Class 1 Zone 1 location. In the past we had used a pre-fabricated enclosure that was UL certified as a whole. This was very expensive and used modbus communication which I'm not to fond of. I'd rather build a panel in-house and have a component-based approval.

I'm thinking if I can design and enclosure with intrinsically safe IO and EEx'e' rated components, then I can get an approval. The trick is that without a certification on the entire enclosure, I'll have to proove that everything down to the connections on the screw terminals is EEx'e'.

Since my larger parent control system is ControlNet, I'm planning on using FlexEx. But I'm no expert in intrinsically safe IO and hazardous area controls. So I have a few questions.


Are there any industrial pushbuttons and lamps that carry EEx'e' ratings on the wire terminations and power modules?

Does the FlexEx render all its outputs intrinsically safe? If so, would an EEx'd' pushbutton or LED that is rendered intrinsically safe by virtue of connection to FlexEx be approved for use in a Zone 1 area, without the enclosure or feed-throughs being EEx'd'?

Could I put the FlexEx IO blocks in a safe area, supply them with safe power, and wire to the field devices in the hazardous area, and connect to the IO with standard copper communication media?

If anyone has any experience with instrinsically safe or hazardous are IO design, your comments would be appreciated.

Thanks
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...for use in a Class 1 Zone 1 location

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I assume your are talking about a Class I, Division 1 area, flammable gases under normal operating conditions. This is a bad one to put any type of arcing or sparking electrical equipment into. The old design rule was to move every sparking device outisde the hazardous area. What the heck is EEx'd? You need to spell it out before I can understand what your are talking about. I assume your are talking about some type of rating for networked equipment?

Basically, to be intrinsically safe, the device must have limited voltage and current. But there are many devices rated for use in Class I, Division 1 that are not intrinsically safe. Usually they have an ignition-proof enclosure.

Could I put the FlexEx IO blocks in a safe area, supply them with safe power, and wire to the field devices in the hazardous area, and connect to the IO with standard copper communication media?

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Certainly you can, as long as the field devices have low voltage and current and no arcing switches, or are in a Class I, Div. 1 rated enclosure. The FlexEX IO is not your big problem here. It can be put in any convenient place, preferably in a non-hazardous location. The field devices are the dangerous components, that usually contain things like limit switches, pushbuttons, pilot lights, contactors, and so on.

If you use the proper power supply and the ControlNet barriers you can place the whole FlexEx I/O adapter and I/O modules in the hazardous area in a NEMA 12 enclosure. Just make sure you read the tech notes on designing a copper ControlNet network that uses the IS barriers (new distance and node limitations). Also, mount the explosion proof power supply right next to the node. That is the way the system is designed to be used, if your low voltage power wiring goes much over 20ft you will have strange problems.

Darren

We have a Class 1 Div 1 room in our plant. We use a PV1000 for the HMI, and don't use PB or Lamps, unless they are EXPLOSION RATED. I will write more tomorrow, my shift is done now,
Chiko everywhere, very expensive installation practices. Best to keep everything out of the room unless qualified for the room.

Also note that the EEX spec that you referenced is closely related to what in the US we would consider "Explosion Proof". Other than it looks like light weight junk to me. Next you referenced FlexEx which is for "intrinsically safe" circuits. For an IS circuit when there are non-powered devices (like push-buttons, limit switches, etc) you are able to use standard components other than it is recommended to use gold plated contacts since an IS circuit does not have enough power to "burn through" any corrosion. For prox switches you want to use NAMUR rated switches since they are designed to operate with the extrem low voltage/current limitations of an IS circuit.

Now for IS stuff, once you get past your seal-offs you are able to use standard construction in theory, but usually the hazardous area has a reason for being rated as hazardous.

Some of the gases, dust, chemicals, explosives, etc can be very corrosive. This can put limitations on your enclosure selection. Also depending on what is going on you may require an extensive grounding system, low conductivity concrete/flooring systems, etc. So if the area you are in requires this level of detail stick with stainless enclosures that you can bond properly.

For IS circuits you want to clearly mark the enclosures, raceways, conduits as containing Intrisically Safe circuits.

Wago has EEX rated terminal blocks.
Hoffman has enclosures that are rated for use with EEX installations.
Stahl has I.S. rated LED pilot lights.
TURK has IS rated proxes.
Banner has IS rated photoeyes.

Of course the basic comments above are for installation in the US, outside the US may require additional limitations.

Darren

By the way, who's standard are you trying to meet? Is this for the UL rating of the panel? If so have you contacted UL and gotten the proper spec for this?

I'm trying to design an installation approved for a Class 1 Zone 1 installation, this is an IEC classification, as opposed to Class 1 Division 1, which is an NEC classification.

The EEx 'edm' IIC T6 etc, etc, is an ATEX marking which is a European marking for the standards met by the device. A device marked EEx'e' is approved for use in a location classified as Zone 1 by IEC.

My dilemma is that I want all my components and installation to meet the EEx'e' increased safety standard by way of manufacturer approvals so that I don't have to pay to have a 3rd party lab to certify my installation. If I can show that component-by-component my installation meets EEx'e' and/or EEx'i' (intrinsically safe) standards through manufacturer's documentation (or a combination of the two), then my surveyor will approve it without requiring a 3rd party lab test.

Maybe the best way is to forget about searching for EEx'e' stuff and go straight for Intrinsically Safe. If I can get I.S. rated pushbuttons and lights, connect to FlexEx I/O, and use the proper barriers, then it looks like a good system. But I wonder if I can get this approved on a component by component basis, or will it require a 3rd party lab card before it can officially be called Instrinsically Safe.

Thanks for the comments so far.

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