Pilot Lights in Intrinsically Safe circuts

It is my understanding that an LED is considered a simple device, making its use fairly simple in an IS application.

However I am running into a problem with this AB PL. Customer went digging for an IS cert, which is not needed and ended up on the phone with AB. According to AB it is not considered a simple device, I am still waiting for additional information from the customer on why.

Anyone have any insight?

The person on the phone probably doesn't understand the context. It is behind a IS barrier, right? Just print out the relevant section on IS and simple apparatus and present that to your customer.

An article form Control Engineering (January 2018).
" It is important to point out that installing a control system in a hazardous area is not a one-man show. The facility is required by law to properly classify any area that may contain an explosive atmosphere. The control-system designer must check with plant engineering, operations or safety personnel and determine the area classification. A facility that appears to be nonhazardous may have several hazardous areas, including explosive fumes or powders, so always check."

TWS said:

An article form Control Engineering (January 2018).
" It is important to point out that installing a control system in a hazardous area is not a one-man show. The facility is required by law to properly classify any area that may contain an explosive atmosphere. The control-system designer must check with plant engineering, operations or safety personnel and determine the area classification. A facility that appears to be nonhazardous may have several hazardous areas, including explosive fumes or powders, so always check."

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Not sure what you mean by this statement, but I did not get a response on how what the control drawing says for the panel mounted devices, as we are about 1yr into the project and this is just now being brought up.

all devices used in a hazardous location must be rated for the environment.
look at your led information for classifications and it should give you a listing.
the rules may have changed since my last class 1 div 1 / class 2 div 2 design.
You also have power limitations after the IS barrier.
regards,
james

mobil1syn said:

It is my understanding that an LED is considered a simple device, making its use fairly simple in an IS application.

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That device, unless it has another sticker somewhere else, isn't intrinsically safe and can't be used as part of a certified intrinsically safe circuit.

Simple apparatus would be a normal contact (like a push button) or an RTD connected to a temperature transmitter.

A simple resistance like a potmeter, for example, although simple can heat up and create an ignition hazard depending on the power rating as well so it's not always a given that something is simple apparatus.

You also don't know whether the LED has resistance or any other type of electronics within it (for protection, for example) that would create a spark hazard.

Lastly, even if it is simple apparatus, you'd have to verify that the length and type (capacitance and inductance) of your cable can be used with the barrier and device. It's never just a matter of sticking a barrier and calling it a day... and it's another world of pain if you're using Zener ones as you have to guarantee some grounding conditions too.

Edit: That device takes in AC... there aren't intrinsically safe AC circuits.

The facility is required by law to properly classify any area that may contain an explosive atmosphere. That is where you start.
The customers determines the classification level your equipment will be installed in. That determines the barrier selection.
The barrier limits the energy to the hazardous area and must be selected based upon the hazards. An oil refinery will have a different classification than say a hydrogen production facility.
Read this: https://www.mtl-inst.com/images/uploads/datasheets/App_Notes/AN9003.pdf.

That particular pilot light is AC or DC. It can be used on an IS circuit with a barrier. As cardosocea stated: "even if it is simple apparatus, you'd have to verify that the length and type (capacitance and inductance) of your cable can be used with the barrier and device. It's never just a matter of sticking a barrier and calling it a day... and it's another world of pain if you're using Zener ones as you have to guarantee some grounding conditions too."

I am an industrial OEM, so getting signals to the edge of the skid for integration in the plant wide control system is where my scope ends, beyond that is the customer which would include the IS system design and Area Classification.

The pilot light has a dual voltage input (I am using 24vdc, which might be where the problem since there has to be some sort of transformer in there ) and is rated for the provided area classification of C1,D2.

If my design is not compliant, that is fine, I just need to know WHY so I can resolve it and file this in the learning experience column.

Thanks for the input.

TWS said:

The facility is required by law to properly classify any area that may contain an explosive atmosphere. That is where you start.
The customers determines the classification level your equipment will be installed in. That determines the barrier selection.

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correct, which is where the confusion comes into the equation. all the control drawings should have been done including my equipment for them to design and build their control system.

Is your system going into a Classified area? If so I think it is your responsibility to make sure it complies with all regulations and safety requirements.

mobil1syn,

While it is true that the facility must define the classification of the plant,
it is YOUR responsibility, i repeat YOUR responsibility to design the controls to meet those specifications! you are also required to supply the control prints, a list of all component part numbers, and all component documentation to the customer so he can verify the validity of your design. the rules may have changed as i said, but i know that if something goes wrong, YOU and YOUR company Will be the scape goat and must prove the validity of the design. I would also check the po to see if the design is required to be stamped by a P.E.
this is what i have had to do in the past.
james

James Mcquade said:

it is YOUR responsibility, i repeat YOUR responsibility to design the controls to meet those specifications! you are also required to supply the control prints, a list of all component part numbers, and all component documentation to the customer so he can verify the validity of your design.
james

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maybe i am not making myself clear. i am in no way trying to sidestep that responsibility or put out a product that could cause harm to anyone. this system is doing gas compression with some serious consequences if something goes wrong. i have control of what is on my equipment, beyond that i dont not. now each project i do, i learn more questions to ask at the beginning of the project to simplify things and avoid headaches later. my goal is to learn and have each project be simpler, better, and constantly chasing that 'perfect' project.

i have a part based on my understanding acceptable for the area classification and controls scheme. i dont have access to AB like our customer does (giant mega company) so when they came back saying AB said no, i was confused and started digging. everything i could find said it was acceptable and the customer has not shared the reason (or even if one was provided) why AB said it was a no go, or if they offered an alternative. IS installations are common, so for AB not to offer a PL for an IS installation seems insane to me.

now during all of the this the local AB rep was able to provide this tech bulletin which should be sufficient evidence that the device is acceptable in its intended use.

mobil1syn,
We are on the same page, i just wanted to alert you to the heartache i had to go through on a project with a customer. may i make a suggestion, along with your documentation, advise the customer on what the barrier limits are as a safeguard. you can also do the following. use rigid conduit with myers hubs at the enclosure, a sealoff within 18 inches of the penetrating wall to the hazardous area, use nema 7,9 pushbutton enclosures, and ab 800h pb's, switches, and lights. they are class 1 div 1. this is what i had to do.
regards,
james

mobil1syn,,
Sorry, i had to run to the line before i could edit my last post.
in regards to your picture, i would not allow the device.
it says class 1, groups a, b, c. it does not say Class 1 Div 1, div 2.
AB is trying to split hairs in this regards, to get the div 1/div 2 rating, they must spend mega bucks. also look at the power limitations of an i.s barrier

regards,
james

James Mcquade said:

mobil1syn,,
Sorry, i had to run to the line before i could edit my last post.
in regards to your picture, i would not allow the device.
it says class 1, groups a, b, c. it does not say Class 1 Div 1, div 2.
AB is trying to split hairs in this regards, to get the div 1/div 2 rating, they must spend mega bucks. also look at the power limitations of an i.s barrier

regards,
james

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James, it was probably hard to read, but it is listed as C1, D2 on the label.