Intrinsically Safe Power for HMI

Hi,
I have a Class 1 Div 2 HMI and would like to supply the 24 Vdc power through an isolation barrier. I cannot seem to find any barriers out there. I even contacted Pepperl and Fuchs, who stated they did not make one.
Has anyone one done something similar? If so what did you use.
I searched the forums, but didn't see anything pertaining to my situation.

How much current does your HMI require? Isolation barriers work by limiting the current. There isn't enough current to cause a spark, usually 100mA or so is the max current available. I'm guessing your HMI draws more than that, so it's not possible.

Ken,
1.2 Amps, I've been looking at a KFD2-SL-4 from Pepperl and Fuchs. My thinking, if I can parallel the circuits to share the amperage. I cannot get a reply back from them. May have to just buy one and try it.

Ken is correct, but I think the current is much less, 10-20ma???

First thing first !
1. classification - class 1 div 2
2. hmi to be used?
is it rated for the environment - you said class 1 div 2.
can is withstand being put in a purged or pressurized enclosure?

no - stop, you are done.
most of the displays will crack / bust when pressurized and expose the
electronic components the gas in the area. doesn't matter that it's div 2,
when the area becomes div 1, we do not need things to go sideways.

there are units out there that will meet this requirement, but they aren't
cheap.
3. since you are class 1 div 2, you will need to go by NEC70, section 500-???
(hazardous locations) and NFPA 496 (Purging and pressurization of
enclosures).
IF you cannot use a nema 7 enclosure and you choose a thinner enclosure,
you must use a nema 4 / 4x enclosure which will meet the purge
requirements.

4. Get the design stamped by a PE to ensure you are covered. detail all items
and materials to be used.

I had to do this in a Class 1 div 1 and class 2 div 1/2 environment at another company.

if the rules have changed or I am incorrect, someone please correct me.
I looked at the spec sheet and in my opinion,the device you have chosen is not an intrinsic safety barrier and there is no classification on the device.
james

I would just use a Class 1 Div 2 rated Power Supply. Automation Direct has a bunch of them. James has made some good points.

You don't have to Purge the panel if you make sure that EVERYTHING in the panel is rated for the C1D2. That includes the Relays, PLC, Ethernet Switch or anything that has wires run to it. For circuit protection you can use C1D2 Circuit Breakers or Class CC Fuses. You can not use the standard "Glass" fuse types. Finally the Panel need to be placed in a Class 1 Div. 2 or unclassified area only. If the area is rated Class 1 Div. 1 rated you will need to choose a different location.

If you purge a C1D2 Panel you can then use it in a C1D1 area. That is how I remember it when I was building UL panels for Hazardous Locations.

forqnc said:

Hi,
I have a Class 1 Div 2 HMI and would like to supply the 24 Vdc power through an isolation barrier. I cannot seem to find any barriers out there. I even contacted Pepperl and Fuchs, who stated they did not make one.
Has anyone one done something similar? If so what did you use.
I searched the forums, but didn't see anything pertaining to my situation.

Click to expand...

I don't think you'll find an intrinsic safety barrier that will supply enough current to power and HMI. That would defeat the whole purpose of IS. Even if you did, unless the device is rated intrinsically safe, it's not considered an IS installation and still can go boom. Why do you want to put it on a barrier exactly?

Bullzi,

Sorry to disagree with you, but the hmi panel must be purged or pressurized, otherwise it must be the nema 7/9 bulky enclosure.

a normal enclosure that gets a hazardous gas in it and has an ignition source will bulge / blow apart where the nema 7 enclosure will withstand an internal fire / explosion.

the rules may have changed, but I would not allow this in the plant even if it were allowed.

james

forqnc said:

Ken,
1.2 Amps, I've been looking at a KFD2-SL-4 from Pepperl and Fuchs. My thinking, if I can parallel the circuits to share the amperage. I cannot get a reply back from them. May have to just buy one and try it.

Click to expand...

First of all, the KFD2-SL-4 is not intrinsically safe. So there's that... you can tell because the field terminals aren't blue (which is standard across several brands). The proof of it being IS is a certificate telling this to you. As you can see, no such certificate exists for this model.

The intrinsically safe barriers are also limited in current and will not power this power supply of yours.

Now for your problem...

Your HMI will have something stating its protection method such as Ex e, Ex nA, Ex nR, etc... that tells you the protection method and how to get it connected. Additionally, it will have a certificate number and in it there will be more information that you must follow to install said equipment.
Since that rating is equivalent to ATEX Zone 2, I'm going to say it is Ex nA or Ex e. With this type of protection, you must route your power with a SWA cable and land it with the right gland (if it's Ex e box, then it's going to be an Ex de gland). Ex nA will likely have similar requirement on the glanding.

The cable with the power, however, must not go through a zone 1 or zone 0 or whatever the equivalent is in the US.

James Mcquade said:

Sorry to disagree with you, but the hmi panel must be purged or pressurized, otherwise it must be the nema 7/9 bulky enclosure.

Click to expand...

If that is the case, the HMI would have that specified in its IECEX rating as Ex p... for that area, I doubt that it is Ex p and as such that it requires purging or pressurisation. Hopefully op can enlighten us with the model number.

cardosocea,

I agree, the hmi MUST have the class / div rating on it.
But the unit still must meet the purge / pressurization requirement in regards to the display.

as I said earlier, the enclosure must be one of the 2. purged or pressurized to keep the gas out of the enclosure to prevent an incident. rigid conduit is required and seal offs also. if the rules have changed, I still would not allow it, ever. I worked in a class 1 div 1/2 area for years and that was the rules.

james

James Mcquade said:

I agree, the hmi MUST have the class / div rating on it.
But the unit still must meet the purge / pressurization requirement in regards to the display.

as I said earlier, the enclosure must be one of the 2. purged or pressurized to keep the gas out of the enclosure to prevent an incident. rigid conduit is required and seal offs also. if the rules have changed, I still would not allow it, ever. I worked in a class 1 div 1/2 area for years and that was the rules.

Click to expand...

Again, we don't have enough information for that. If the HMI is a pressurised unit, it will be stated in the IECEX rating as Ex p. If it is an Ex n or e and is installed in a Class 1 Div2 area, then it does not require pressurization.

However, if you must install said HMI (and it's not a touch screen one) in a class 1 div 1 area, then you must put it in a pressurised/purged cabinet.

If your purged/pressurised cabinet is Ex px, it changes the internal of the cabinet from Class 1 Div 1 to non-hazardous, if you do with py, it turns the inside of the cabinet from class 1 div 1 to class 1 div 2.

In this situation, you are right that it must have pressurised/purged cabinet... but OP hasn't given us any information about this so we cannot say for sure which is which.

James,
I understand what you are saying but you need to take into account the classification definitions themselves. Sounds like you may be thinking of a Class 1 Division 1 area where Explosive vapors exist all the time. Class 1 Div. 2 is for areas that will see hazardous vapors only in abnormal conditions. So vapor would only exists if there was a spill or upset.

For any component to get C1D2 approval it must be able to be in that kind of environment and not ignite a fire. These types of components are designed to not get to hot and have some kind of seal that would keep a sparking device (relay) from allowing vapor to get into it and cause a fire. They are built and tested for just this type of environment.

I sell many different devices that are in NEMA 4/4X Enclosures that are Class 1 Div. 2 rated and are able to be installed in the field exactly the way they are built. No pressurization or NEMA 7 enclosures required. I do sell a lot of C1D1 rated devices too. Most of the time this is because the manufacture just make one piece of equipment that can be put anywhere so they just make the C1D1 version.

In all the plants I have worked in (Refineries, Loading Racks, Crude Facilities) about 90% of the areas fall into C1D2 or unclassified. I think that sometimes just to be "Extra Safe" they will use C1D1 NEMA 7 enclosures (even when it is just full of terminal blocks) and that is fine. Also when they come to me and ask for a piece of equipment and I give them 2 prices, one for C1D1 and one for C1D2 they almost always take the much lower cost D2 option.

Agreed.

we need more information.
james

Bullzi said:

Also when they come to me and ask for a piece of equipment and I give them 2 prices, one for C1D1 and one for C1D2 they almost always take the much lower cost D2 option.

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This is downright scary... isn't there any regulation in the US demanding a hazardous area risk assessment that outlines where you have C1D1 or D2 before you install gear in it?

I do find it interesting how the american system only separates the vapours into 2 zones instead of the 3 ATEX ones.

cardosocea,

yes there is.

the first step in what is trying to be done is find am hmi that will meet the requirements. Allen Bradley makes several panelview terminals, but their issue several years ago was pressurization of the unit, the display would crack according to AB.

there is a hmi terminal that meets his requirements that's about $10k I cannot remember the name.

once this is figured out, you do the piping, then do the risk assessment, finally get the project stamped by a PE. this is what I had to do at my former worksite that moved north and I was let go.

james

WOW, lots of good information from everyone. Thank you

Sorry for not including the model HMI, in OP, to avoid confusion.
It's an AB Panelview Plus7 mod. 2711P-T7C21D8S.

This is on a simple push button station, Stop, Start, Jog, Speed pot and E.stop. All push buttons go through IS (Blue terminals) barriers to the PLC. This is in a nema 1 enclosure which is installed in a safe/unclassified area. Push button panel is a nema 4X SS, all connections to PB station are sealed after final testing.

I realize Class 1 Div 1 is a whole different subject. We have Class 1 Div 1 rated tablets for that. But that's another project when I get to it.

The question was raised regarding the power supply to the HMI. As I have learn't from research, and now here, IS barriers are not for this purpose.
So is the solution just to use a Class 1 Div 2 power supply?