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Using I.S Barriers With a Non-I.S Sensor?

05/29/2018 3:38 PM

Hello,

I want to install a discrete sensor in a class 1 div 2 area. It needs 24VDC input and will give a discrete out of 24VDC as well that goes to a PLC. It's a Keyence AI pattern matching sensor and specifically states that it cannot be used in a hazardous location.

*I know that probably means I have to look elsewhere for a suitable sensor but just looking to get a second opinion from more experienced people*

My question is this, can I simply use it along with a Pepperl+Fuchs or Allen Bradley I.S barrier and expect it to be suitable for the hazardous area?

Here's some input and output specs from the sensor manual -

https://imgur.com/VfioC2i

Thanks

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#1

Re: Using I.S barriers with a non-I.S sensor?

05/29/2018 4:05 PM

Why do think Keyence specifically states it can't be used in a hazardous area? It says "can't be used" not "can be used if you do this".

I think I would go with the manufacturers warning and not try to make a non intrinsically safe sensor by design, intrinsically safe by modification.

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#2

Re: Using I.S barriers with a non-I.S sensor?

05/29/2018 5:25 PM

Just paint them HOT PINK and you'll be fine.

Oh, and DO NOT power them up.

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#3

Re: Using I.S barriers with a non-I.S sensor?

05/29/2018 6:45 PM

Nope, only if the sensor is a simple apparatus device (like a switch for example) which doesn't have any energy storage capability, or an electronic sensor which is already certified.

If the sensor has any energy storage capability then adding an IS barrier or galvanic isolator to the output won't provide protection because the energy storage element in the sensor (for example a capacitor) could easily store enough energy to create a spark big enough to ignite the flammable gas atmosphere the sensor is stored in.

Your best bet would be to look into alternative Zone 1 certified sensors.

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#4

Re: Using I.S barriers with a non-I.S sensor?

05/30/2018 2:33 AM

No, because it is a device that stores sufficient energy to create an incendive spark; it is neither suitably certified nor "simple apparatus" under the standards. Adding an i.s. barrier will therefore not protect the circuit.

Don't do it.

Apply for training in the selection and use of electrical equipment in potentially explosive atmospheres.

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#5

Re: Using I.S barriers with a non-I.S sensor?

05/30/2018 6:54 AM

Thanks all. I wasn't planning to install the same sensor but just wanted to make sure the easy way out is not feasible.

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#6
In reply to #5

Re: Using I.S barriers with a non-I.S sensor?

05/30/2018 11:47 AM
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#7
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Re: Using I.S barriers with a non-I.S sensor?

05/30/2018 1:28 PM

Thanks for that laugh!

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#8

Re: Using I.S Barriers With a Non-I.S Sensor?

06/07/2018 8:49 AM

You guys are funny.

Anyway, just to provide an update, I am planning to use an explosion proof enclosure with the same sensor and wire it according to code.

Would have preferred I.S but couldn't find a vision sensor from any manufacturer that certifies that.

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#9
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Re: Using I.S Barriers With a Non-I.S Sensor?

06/26/2018 2:46 AM

<...an explosion proof enclosure with the same sensor...>

Two problems with that:

  1. If the enclosure is certified <...explosion proof...>, then it will not be possible to adjust or even observe the transmitter inside it while energised.
  2. The transit between the inside and the outside of the enclosure needs to be considered in the context of not transmitting a flame from inside to outside. For that, the transit needs to be correctly designed and installed, using certified equipment.

This is not a DIY job.

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#11
In reply to #9

Re: Using I.S Barriers With a Non-I.S Sensor?

06/26/2018 7:53 AM

Appreciate your concern but I know it's not a DIY job. I have certified technicians working on it. We'll be using proper conduits and fittings according to NFPA 497 and NEC 500-510.

There's a sensor head and a separate amplifier somewhat similar to a remote mounted traditional transmitter. The amplifier has the display and the buttons. My plan is to mount the sensor head inside the explosion proof enclosure where it'll remain untouched. Using a remote cable, the amplifier will be placed into a panel located outside the classified area. So the explosion proof enclosure will not be opened under normal circumstances.

If ever we have to replace the sensor head for any reason, we get a hot work permit and make sure it's safe to open the enclosure.

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#13
In reply to #11

Re: Using I.S Barriers With a Non-I.S Sensor?

10/04/2018 3:00 AM

In that case, the sensor will be measuring what is going on inside the enclosure, and not outside it.

D'oh!

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#10
In reply to #8

Re: Using I.S Barriers With a Non-I.S Sensor?

06/26/2018 5:25 AM

How did the training on Electrical Equipment in Potentially Explosive Atmospheres go?

"How we deal with death is at least as important as how we deal with life." --CAPTAIN KIRK, Star Trek II: The Wrath of Khan

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#12
In reply to #10

Re: Using I.S Barriers With a Non-I.S Sensor?

06/26/2018 7:57 AM

I requested it to my superiors and they are happy to pay for it. Now it's just down to me to figure out a suitable course nearby.

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