Epoxy on floor hazardous floor question.

[powerpete69]

I received the question below in a kind of vague fashion. But can one of you hazardous gurus weigh in on this and possibly quote the code?
I guess the question is: does the floor need to be conductive to keep things grounded...perhaps?
Any help would be great.

PowerPete69,
I am working on a project, which will include repair of the floor in extrusion and weighing areas. One possible solution for the repair is to cover the old concrete with epoxy resine. However, in this case the floor will not be conductive any more. I am wandering if there is any Avient requirement or guideline to have conductive floor in Hazardous (Classified) Area to reduce the risk of dust explosion. If yes, could you please send me detailed desciption about the requirements.

 

[gadfly56]

I received the question below in a kind of vague fashion. But can one of you hazardous gurus weigh in on this and possibly quote the code?
I guess the question is: does the floor need to be conductive to keep things grounded...perhaps?
Any help would be great.

PowerPete69,
I am working on a project, which will include repair of the floor in extrusion and weighing areas. One possible solution for the repair is to cover the old concrete with epoxy resine. However, in this case the floor will not be conductive any more. I am wandering if there is any Avient requirement or guideline to have conductive floor in Hazardous (Classified) Area to reduce the risk of dust explosion. If yes, could you please send me detailed desciption about the requirements.

If the floor was previously conductive to reduce the hazard of static electricity, any alteration should preserve whatever the design conductivity is. When I worked at Hercules, we solved this problem by installing lead floors.

 

[powerpete69]

If the floor was previously conductive to reduce the hazard of static electricity, any alteration should preserve whatever the design conductivity is. When I worked at Hercules, we solved this problem by installing lead floors.

I would think having a conductive floor would remove any potential static electricity from your body. Ignition sparks not good in explosive areas.
Why did you use lead as opposed to something else? Is there any way to repair concrete without removing conductivity?

Hoping that rbalex weighs in here.

 

[gadfly56]

I would think having a conductive floor would remove any potential static electricity from your body. Ignition sparks not good in explosive areas.
Why did you use lead as opposed to something else? Is there any way to repair concrete without removing conductivity?

Hoping that rbalex weighs in here.

We used lead because it was conductive enough, and it would deform if you dropped a tool, reducing the possibility of an impact ignition if there happened to be a drop or two of errant nitroglycerin, nitrocotton, or gunpowder on the floor.

Concrete itself doesn't have very good conductivity.

These guys do installs:

Conductive Epoxy Flooring | Anti Static Solutions for Manufacturing Plants

Conductive floor systems; Specialists in epoxy/urethane for electronics, hazardous processing, storage, munitions. Nationwide installation.

epfloors.com

Looks like you can go to Sherwin Williams for a product:

Static Control | High Performance Flooring | Sherwin-Williams

Is your facility sensitive to electro-static discharge? Static control epoxy flooring and coatings can help you safely dissipate electro-static discharge.

industrial.sherwin-williams.com

These are complicated flooring systems, and I would not recommend you trying to do it yourself.

 

[petersonra]

It does not take much in the way of conductivity to eliminate static electricity. Concrete is a lot more conductive than you think. You can easily trip a GFCI via concrete and that is only 5 mA.

It seems to me that if the previous risk analysis suggested the need for special coating to make the floor more conductive, then it would seem appropriate to continue that approach.

 

[gadfly56]

It does not take much in the way of conductivity to eliminate static electricity. Concrete is a lot more conductive than you think. You can easily trip a GFCI via concrete and that is only 5 mA.

It seems to me that if the previous risk analysis suggested the need for special coating to make the floor more conductive, then it would seem appropriate to continue that approach.

More properly, I would say "can be" more conductive than you think, depending on the moisture content. If static dissipation is the goal, I don't think you want to be depending on uncontrolled variables as part of your safety plan.

 

[zbang]

https://www.arpnjournals.org/jeas/research_papers/rp_2016/jeas_0516_4215.pdf

This literary study indicates that moist concrete behave as a semiconductor with resistivity of the order of 10⁵ ohm-mm while oven-dried concrete behaves as an insulator with resistivity of the order of 10¹² ohm-mm.

Add some rebar and it gets pretty conductive.

IIRC, you only need a few meg-ohms to dissipate a static charge.

 

[petersonra]

More properly, I would say "can be" more conductive than you think, depending on the moisture content. If static dissipation is the goal, I don't think you want to be depending on uncontrolled variables as part of your safety plan.

Did you read what I said in the second paragraph of my response?

 

[powerpete69]

Ahhhh....thank you.
I will suggest the two conductive epoxy's listed above.

 

[gadfly56]

Did you read what I said in the second paragraph of my response?

Yes I did, and I agree. I just didn't want some casual reader to conclude that bare concrete was just fine under every circumstance. It happens; the TLDNR limit for some folks is amazingly short.

 

[powerpete69]

I just received the following question in regards to hazardous/conductive rating epoxy.
Hoping one of my super smart colleagues can add some insight to the question.
I should probably ask if there is an area classification drawing as well.
But here is the question:

"Should we cover the whole production floor with conductive epoxy? Or is there a defined distance around the Hazardous (Classified) Area, where we need the conductive floor? I mean when the person walking in the nonconductive part, he can potentially charge himself with electricity. Does this electricity discharge shortly after he walks a few steps on the conductive floor? Is there any practical guideline for that?"

 

[powerpete69]

To answer my own question, I would think we want to extend the conductive floor beyond the area classification zone. That way if someone is electrically charged coming from elsewhere, it would spark outside of the area classified zone. But how far out....don't recall seeing that in the NFPA 497 or 499.

 

[rbalex]

To answer my own question, I would think we want to extend the conductive floor beyond the area classification zone. That way if someone is electrically charged coming from elsewhere, it would spark outside of the area classified zone. But how far out....don't recall seeing that in the NFPA 497 or 499.

That's because it isn't there.

I'm surprised no one mentioned Section 500.4 IN No. 2 or Section 501.3. You are not really dealing with equipment, but rather grounding and bonding.

 

[powerpete69]

That's because it isn't there.

I'm surprised no one mentioned Section 500.4 IN No. 2 or Section 501.3. You are not really dealing with equipment, but rather grounding and bonding.

Thanks. I looked thru the 80 pages of NFPA 77-2019 from 500.4 Informational note 2. It talks a great deal about static electricity, but does not mention how far past the area classification line you should go with conductive floor.

I could not find 501.3. My NFPA 70 NEC code book 2020 only has sections 501.1 and 505.5?

I did request an area classification drawing from them if possible. So we can at least know what we are talking about.

 

[gadfly56]

Thanks. I looked thru the 80 pages of NFPA 77-2019 from 500.4 Informational note 2. It talks a great deal about static electricity, but does not mention how far past the area classification line you should go with conductive floor.

I could not find 501.3. My NFPA 70 NEC code book 2020 only has sections 501.1 and 505.5?

I did request an area classification drawing from them if possible. So we can at least know what we are talking about.

That should really have been step 1.

It sounds like there isn't any real demarcation for the explosion hazard area, like a wall. Is that the case? It's more like an area inside a much larger open plan production floor?

 

[powerpete69]

That should really have been step 1.

It sounds like there isn't any real demarcation for the explosion hazard area, like a wall. Is that the case? It's more like an area inside a much larger open plan production floor?

We won't know until they provide drawing or at least some sort of sketch of the room. I guess the short answer would be to cover the entire concrete floor with conductive epoxy. But would prefer the exact solution.

 

[rbalex]

Oops-Sorry Section 501.30. There’s more or less a hint at the end of Section 501.30(B)(1)(b)with respect to how far the bonding system needs to be. Essentially you need a static drain bond all the way to the boundary(s).

“How far past the boundary?”, you may ask. Just right up to the edge. In my early days of learning we would question how far past the boundary must we install arc-making equipment? The answer is you can put it just outside in unclassified location at the edge of the boundary. “You got to draw the line somewhere.”

 

[gadfly56]

Oops-Sorry Section 501.30. There’s more or less a hint at the end of Section 501.30(B)(1)(b)with respect to how far the bonding system needs to be. Essentially you need a static drain bond all the way to the boundary(s).

“How far past the boundary?”, you may ask. Just right up to the edge. In my early days of learning we would question how far past the boundary must we install arc-making equipment? The answer is you can put it just outside in unclassified location at the edge of the boundary. “You got to draw the line somewhere.”

You might want to go at least slightly over the minimum, just to keep the lawyers happy.

 

[rbalex]

You might want to go at least slightly over the minimum, just to keep the lawyers happy.

Possibly, but they wouldn’t be able to come up with any standard to justify it.

 

[gadfly56]

Possibly, but they wouldn’t be able to come up with any standard to justify it.

The process is the punishment. Do a little extra work up front to avoid giving a deposition later.