PLC and HMI in a Explosion Proof Enclosure

[trolex]

Hi everyone,

Can someone tell me if there is a way to use a PLC+HMI in a NEMA 7 enclosure (explosion-proof enclosure)?

Hazardous Location is Class I, Division 2, Group D.

I have read many posts but not sure they usually suggest using a purge system which is not my case since I don't have the possibility to provide purged air to the enclosure.

Also, I have also read that "a window kit with interfacing pushbuttons could be used but HMI shall be able to use a PLC register for the screen selector. But not all HMI has the ability to reference a pointer register within the PLC for screen navigation and that is to be taken into account when selecting PLC/HMI brands."

Although I understood the main point I am not very familiar with this solution. If that is possible, how is a window kit with interfacing pushbutton? I could not find anything about that.

Also, I need to use Allen Bradley Compact Logix PLC with the 7" Panel view from Allen Bradley as well.

However, I don't know if Allen Bradley HMI has the ability to reference the pointer register mentioned before.

If any other method available, I would be happy to read any possible suggestions.

 

[thebard3]

Class 1 Div 2 does not require the use of explosion proof enclosures. Lots of PLC and other automation equipment including pushbutton and relay contacts are classified for C1D2 area. If everything is so rated, then no other design considerations need to be employed. Usually though, you'll find that something you use, (terminal, power supply, relay, etc.) isn't rated so then you have to purge the enclosure. Also wireways have to be sealed and there are some very specific code requirements on how that's to be done.
Some HMI terminals are also rated for C1D2 area. If it's not, you cannot use a cover/window kit unless it is designed and rated for the area classification. I've seen it done but it's not kosher.

Brad Waybright

It's all okay as long as it's okay.

 

[thebard3]

So far as referencing 'pointer register', I think you're right that the PanelView 7 doesn't include that organically like an old panelview terminal. There are a number of ways you can mimic that, though. I would probably use the navigation buttons to set a register value based on what screen selection was last made. You can also use that value for visibility animation to display whatever particulars are required for the screen selected if you'd like.
BTW, I think that PanelView Plus 7 terminal is rated for C1D2 area, but not for a purged enclosure. Vartech makes a touch monitor and panel PC that is so rated. This won't run the *.mer file that you'd use for a PanelView terminal. We have FTView distributed system and that requires a client license for each terminal. However you will also need licenses for the rest of the FTView services too. If you only have one HMI then this is definitely not the best option. You can also use FTView stand-alone application but again, the licenses are pricey to say the least.

Brad Waybright

It's all okay as long as it's okay.

 

[trolex]

Thanks, thebard3 for your response.

Regarding the first comment, you mentioned "If everything is so rated, then no other design considerations need to be employed". Then what about the enclosure, Can I put everything in a NEMA 4X one? Or still, need to use another kind of enclosure (increased safety for example)?

About this comment: Usually though, you'll find that something you use, (terminal, power supply, relay, etc.) isn't rated so then you have to purge the enclosure. Is there a way to make sure these elements are also rated for the area so that I won't need a purge system. As I mentioned, no air is available for me to use.

PD: Both the PLC and HMI are Class I, Div 2 Rated in this case.

 

[djs]

If everything going into the enclosure is rated Class 1 Division 2, there there is no restrictions on the enclosure rating. You can even use type 1. The point here is that everything, and I mean everything going into the enclosure must have the C1D2 rating.

 

[buzzp]

I responded but in the other thread...at least I thought. Cross posting causes mass confusion...

 

[trolex]

Sorry for the confusion buzzp and thanks for the reply djs.

Actually, I did not notice it was also you from the previous post.

In any case, I can find different opinions on if a NEMA 4x enclosure can be used or not. Someone also told me that if everything is rated, less restricted enclosure could be used as well. But I cannot find any statement in electrical codes where this is mentioned.

Ideally, I would prefer to use the Explosion-proof enclosure but as mentioned I found it quite complicated and need more advice on it. Also, I left an unanswered question in another post for you. If you know something let me know.

 

[thebard3]

C1D1 and C1D2 requirements are very different. We always use Nema 4X enclosures for C1D2 classification. If any equipment contained is not rated, then we purge the enclosure. We typically only have problems with solenoid valve manifolds. Most everything else is available to meed that classification. Manufacturer's specification sheets will indicate if it meets the requirement or not.

Classified area rules are complex, specific, and change regularly. I'm sure they also vary by locale. You should have your design reviewed and approved by a registered Professional Engineer.

Brad Waybright

It's all okay as long as it's okay.

 

[thebard3]

One other item to consider- If you punch a hole in an explosion proof enclosure to install something that is not rated for C1D1 area, the enclosure no longer meets that specification. In other words, if your C1D2 HMI penetrates the enclosure, then the XP rating is lost.

Brad Waybright

It's all okay as long as it's okay.

 

[danw2]

Like the others say, all the bits and pieces have to be C1D2.

When we have C1D2 panels made for our customers, the panel shop first has to build them to UL 508A as a precursor to C1D2.

If the end user does not wants or needs a UL cert/label for C1D2, the panel shop signs the drawing as C1D2 based on all the documentation from the component vendors citing C1D2.

If the end user wants or needs a UL cert/label for C1D2, then they pay the premium for the UL guy to actually go out and look at the collection of panel's component docs to confirm that all the bits and pieces are all C1D2 rated. In our area that's about $600 for the trip.

It costs more for 508A and more again for C1D2, but it's far less expensive than XP.

Talk to your panel shop.

 

[buzzp]

I believe MSHA requires XP and I fall under their regulations, including the 1968 version of the NEC (no joke). I'll try to find some time to revisit the page turner suggestion, etc. that I told you about in the other thread and give you some more details...its been 6 years since I did this.

 

[jraef]

Just FYI, CompactLogix 5380, 5370 and 1768 controllers ARE UL listed for Class 1, Div. 2, Groups A-D. But the 5480 controllers are NOT so listed.

The PanelView 5000 5510 series are Cl1 Div2, the 5310 are not. But if this is outdoors, the 5510 is only rated for N4x if it is indoors. As a general rule, outdoor HMIs are never that good of an idea without significant sun shading.

The PanelView Plus 7 ArmorViews (2711P) are both Cl1 Div2 and not restricted to indoor N4X.


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