Classified Receptacle

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rbalex

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I’ve been trying to figure out how to address this thread without offending some people that I have a high regard for. Still it seems several commenters are “shooting from the hip.” Hazardous locations aren't "rocket science" but they aren't "just common sense" either.

My initial response (post # 6) was the forum can’t do the electrical area classification for the OP and someone familiar with the process should do it and the rules for Class II receptacles and attachment plugs are found in Section 502.145. Maybe I should have said “someone familiar with the process and qualified to do so should do it.” Otherwise it is still correct.

Since then there have been several comments that have been in error or misleading, usually by trying to apply purely Class I concepts to Class II or by defining who is qualified to do the electrical area classification.
  • During my term on them, both the API Subcommittee on Electrical Equipment’s Task Force for API RP-500 & 505 and the NFPA Technical Committee for Electrical Equipment in Chemical Atmospheres (NFPA 496, 497 & 499) were made up entirely of the electrical discipline.
  • Class II, Division 1 is effectively defined as any Group E; and for Groups F & G, it is a moderate to dense dust cloud or a dust layer of 1/8” or greater. Class II, Division 2 for those Groups is no visible cloud, but a visible dust layer less than 1/8”. Dust collecting techniques can affect the envelopes as well. The general envelopes are shown in NFPA 499.
  • LEL is undefined in Class II.
  • One concept common with Class I and Class II is "close" to a classified location source isn't enough - you have to draw the line somewhere.
  • At one time the NEC required Zone classified locations to be done by a PE; the NEC no longer does but FedOHSA still requires it. It can be done by anyone qualified to do so, no matter what the discipline.
  • I definitely consult with other disciplines; but, in the end, it is has always been my name and seal on the electrical area classification drawings.
 
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kwired

Electron manager
Location
NE Nebraska
I?ve been trying to figure out how to address this thread without offending some people that I have a high regard for. Still it seems several commenters are ?shooting from the hip.? Hazardous locations aren't "rocket science" but they aren't "just common sense" either.

My initial response (post # 6) was the forum can?t do the electrical area classification for the OP and someone familiar with the process should do it and the rules for Class II receptacles and attachment plugs are found in Section 502.145. Maybe I should have said ?someone familiar with the process and qualified to do so should do it.? Otherwise it is still correct.

Since then there have been several comments that have been in error or misleading, usually by trying to apply purely Class I concepts to Class II or by defining who is qualified to do the electrical area classification.
  • During my term on them, both the API Subcommittee on Electrical Equipment?s Task Force for API RP-500 & 505 and the NFPA Technical Committee for Electrical Equipment in Chemical Atmospheres (NFPA 496, 497 & 499) were made up entirely of the electrical discipline.
  • Class II, Division 1 is effectively defined as any Group E; and for Groups F & G, it is a moderate to dense dust cloud or a dust layer of 1/8? or greater. Class II, Division 2 for those Groups is no visible cloud, but a visible dust layer less than 1/8?. Dust collecting techniques can affect the envelopes as well. The general envelopes are shown in NFPA 499.
  • LEL is undefined in Class II.
  • One concept common with Class I and Class II is "close" to a classified location source isn't enough - you have to draw the line somewhere.
  • At one time the NEC required Zone classified locations to be done by a PE; the NEC no longer does but FedOHSA still requires it. It can be done by anyone qualified to do so, no matter what the discipline.
  • I definitely consult with other disciplines; but, in the end, it is has always been my name and seal on the electrical area classification drawings.

I was not in any way attempting to classify the OP's location, but if anything give him some food for thought that may help understand why his application is or is not classified in a particular way. Op should either have it classified by someone qualified to do so or do his install for worst case conditions. I think it is fairly obvious it will be a class II location if it is classified, and worst case would be treat it as if it were class II div 1. Hard part about his outdoor installation may be where do you set a boundary? If you have been around grain handling facilities there is chaff and other particles floating in the air several hundred feet away sometimes, but it is not at a hazardous location level either.
 

don_resqcapt19

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If that were the case then there would likely be no self service gas stations, and the attendants would be wearing this equipment.
No...very few of the areas that are classified as Division 1 have levels anywhere near LEL under normal conditions. Take a look at some of the MSDS for any flammable product. An example would be gasoline. The LEL is 1.4%, the Short Term Exposure Limit is 0.05%.

I have never been in a grain elevator or feed mill where the environment was that bad, yet it was deemed a hazardous location and we used HL wiring methods.
Yes, the areas are required to be classified because it is possible that there would be a concentration of dust high enough to be in the ignitable range, or because of house keeping, a dust hazard area automatically becomes a Division 1 area if dust is allowed to accumulate to 1/8" or more.
 

iceworm

Curmudgeon still using printed IEEE Color Books
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EE (Field - as little design as possible)
... Since then there have been several comments that have been in error or misleading, usually by trying to apply purely Class I concepts to Class II or by defining who is qualified to do the electrical area classification.
...
Yes, I did that. In my defense, I did note my experience and bias in the first sentence my comments. In retrospect my comment about getting a %LEL meter for a class 2 area, probably does not apply - I've never seen one - don't even know if one is made.

ice
 

don_resqcapt19

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retired electrician
I could not find the reference to the MEC (minimum explosive concentration) for combustible dusts being not able to see you hand with your arm extended, but did find a number of references saying that, in general, the MEC is enough dust in the air that you cannot see a 25 watt light from 6 feet away.
 

iceworm

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If the atmosphere is above LEL you are probably not doing any work....many flammable vapors are IDLH (Immediately Dangerous to Life and Heath) at about 10% of LEL. It is my opinion that no one should ever enter a Class I, Division 1 location unless they have respiratory PPE suitable for the product(s) used in the area.

kwired said:
... If that were the case then there would likely be no self service gas stations, and the attendants would be wearing this equipment. ...

No...very few of the areas that are classified as Division 1 have levels anywhere near LEL under normal conditions. ...
Don -
Your two comments don't match.

When I was doing this for a living, one would take a %LEL meter, sniff the area, if clear, go to work, meter stays running right next to the tech. No escape bottle unless also a confined space. Confined space changes the rules alot.

I don't do much tool work these days, but the current crop of techs and safety practices have not changed much - alot better meters though.

I do not intend this comment to apply to Class2 areas.

ice
 

don_resqcapt19

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Don -
Your two comments don't match.

When I was doing this for a living, one would take a %LEL meter, sniff the area, if clear, go to work, meter stays running right next to the tech. No escape bottle unless also a confined space. Confined space changes the rules alot.

I don't do much tool work these days, but the current crop of techs and safety practices have not changed much - alot better meters though.

I do not intend this comment to apply to Class2 areas.

ice
While most Division 1 areas don't normally have concentrations anywhere near LEL, there is no way an employeer could ever defend a death or injury of an employee working in a Class I, Division 1 area without PPE for the hazard.

I know that my friend Robert, who is an expert on these things does not agree with me on this, but I just don't see how you could defend classifing an area as Division 1 and then sending someone it that area without PPE for the known hazard.
 

iceworm

Curmudgeon still using printed IEEE Color Books
Location
North of the 65 parallel
Occupation
EE (Field - as little design as possible)
No...very few of the areas that are classified as Division 1 have levels anywhere near LEL under normal conditions. ...

... An example would be gasoline. The LEL is 1.4%, the Short Term Exposure Limit is 0.05%. ...

While most Division 1 areas don't normally have concentrations anywhere near LEL, ....
I suggest going a bit further. Most Div 1 areas don't normally have a percentage anywhere near the STEL.. It only takes 1 hour is 8000 to be classified as Div 1 (I likely got the number of hours wrong. I don't remember exactly. APIRP 500 - I think and it is about that number)

... there is no way an employeer could ever defend a death or injury of an employee working in a Class I, Division 1 area without PPE for the hazard. ....
That's true. But I don't think that one could defend a death or injury even if they did have an escape bottle

What one could defend is not putting anyone in harm's way by providing continuous monitoring. The trick is not being able to work while the %LEL is up, but monitoring and not working if the %LEL is up - rather ventilate, clear, then work (if the %LEL is up). Div 1 doesn't matter. One does not work if the concentration is other than below (what ever the acronym is for long term exposure). Does not apply to in-and-out work like reading a meter, or operating a valve .

Remember your service station comment. While you are filling your car you are likely in the Div 1 envelope. If not today because of vapor recovery - you likely were yesterday.

ice
 

kwired

Electron manager
Location
NE Nebraska
No...very few of the areas that are classified as Division 1 have levels anywhere near LEL under normal conditions. Take a look at some of the MSDS for any flammable product. An example would be gasoline. The LEL is 1.4%, the Short Term Exposure Limit is 0.05%.


Yes, the areas are required to be classified because it is possible that there would be a concentration of dust high enough to be in the ignitable range, or because of house keeping, a dust hazard area automatically becomes a Division 1 area if dust is allowed to accumulate to 1/8" or more.
I know the dust hazard area really depends on the present mixture and that good housekeeping may change the classification in some cases.



Remember your service station comment. While you are filling your car you are likely in the Div 1 envelope. If not today because of vapor recovery - you likely were yesterday.

That is kind of what I was thinking with the filling station comment, everything in vicinity of dispenser is CL1 D1 (need to look up exact distances, but we have thousands of self service stations all over the place and nobody (especially self serve customers) is wearing any protective equipment while they are in this classified area.
 

rbalex

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...
That is kind of what I was thinking with the filling station comment, everything in vicinity of dispenser is CL1 D1 (need to look up exact distances, but we have thousands of self service stations all over the place and nobody (especially self serve customers) is wearing any protective equipment while they are in this classified area.
Yes you definitely do. See Diagram 514.3. The aboveground external to the dispenser hasn't been Division 1 for ages; in fact, I can't remember when they ever were. My disagreement with Don has simply been that not all Division 1 locations are toxic, but he's right that most are.
 

kwired

Electron manager
Location
NE Nebraska
Yes you definitely do. See Diagram 514.3. The aboveground external to the dispenser hasn't been Division 1 for ages; in fact, I can't remember when they ever were. My disagreement with Don has simply been that not all Division 1 locations are toxic, but he's right that most are.
That is what happens when I try to go off of memory, especially on something I don't do very often. I could have sworn there was a DIV 1 area that extended at least where the dispensing hose reaches. I did know that it was DIV 1 inside the unit or inside pits, etc.
 
Yes you definitely do. See Diagram 514.3. The aboveground external to the dispenser hasn't been Division 1 for ages; in fact, I can't remember when they ever were. My disagreement with Don has simply been that not all Division 1 locations are toxic, but he's right that most are.

Without examining the specific parameters of the chemical, such as LEL and related toxicity levels, a definitive statement can not be made. The two has no direct relationship to each other, albeit overlapping areas may exist. It is also possible that toxicity level exist BEFORE LEL is even reached.

Having said that, I've heard Don's stipulation a long time ago and it seems to persist as an 'urban myth' within the general technical community, but certainly not at the level of people with Bob's experties.
 
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don_resqcapt19

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...
That's true. But I don't think that one could defend a death or injury even if they did have an escape bottle ...
I would agree...having an escape bottle would not be good enough...in my opinion, if you are in a Class I Division 1 area you need to be using PPE suitable for the hazard...not just have it available. In the case of flammable products that may also require PPE to protect you from fire as well as inhalation hazards.
 

don_resqcapt19

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Without examining the specific parameters of the chemical, such as LEL and related toxicity levels, a definitive statement can not be made. The two has no direct relationship to each other, albeit overlapping areas may exist. It is also possible that toxicity level exist BEFORE LEL is even reached.

Having said that, I've heard Don's stipulation a long time ago and it seems to persist as an 'urban myth' within the general technical community, but certainly not at the level of people with Bob's experties.
Pick a MSDS and look at the IDLH or STEL and compare it to the LEL...in many many cases you are above IDLH or STEL at less than 10% of LEL.
Styrene...LEL 1.1%, STEL 100ppm (0.01%)
Acetone...LEL 2.6%, STEL 750ppm (0.075%)
Ammonia...LEL 16%, STEL 35ppm (0.0035%)
1,3-butadiene...LEL 2%, STEL 5ppm (0.0005%)
Methyl ethyl ketone...LEL 1.8%, STEL 300ppm (0.03%)

When I did my HazMat training for the fire service, I don't think we ever looked up a flammable product that had a STEL that was even close to the LEL...they were always much lower.
 

hurk27

Senior Member
Pick a MSDS and look at the IDLH or STEL and compare it to the LEL...in many many cases you are above IDLH or STEL at less than 10% of LEL.
Styrene...LEL 1.1%, STEL 100ppm (0.01%)
Acetone...LEL 2.6%, STEL 750ppm (0.075%)
Ammonia...LEL 16%, STEL 35ppm (0.0035%)
1,3-butadiene...LEL 2%, STEL 5ppm (0.0005%)
Methyl ethyl ketone...LEL 1.8%, STEL 300ppm (0.03%)

When I did my HazMat training for the fire service, I don't think we ever looked up a flammable product that had a STEL that was even close to the LEL...they were always much lower.

This has been the results of much of the training at work, since CO is one of the major gas's we deal with we will never see the LEL/LFL levels before the IDLH is way over the safe limit, in general CO has a 12% LEL with a UEL of 75% our LEL meters are set to alarm at 10% LEL I think, so a mixture of 120,000ppm LEL is going to be way above the 75ppm first alarm our CO Toxi-Pro's are set to warn us with a get out setting at 200ppm.

Also what I find strange is very little is mentioned about the temp at which the LEL rating is at, we see Diesel fuel has a LEL of .6 but Gasoline has an LEL of 1.4, but how is this possible without the temperature of the LEL rating also put in to the equation, this part I do not understand?

If we have a fuel that is non-explosive such as Diesel at room temperature, how can it have a lower LEL then gasoline?, is this why we can't use the LEL ratings of the combustible mixture for classification of the zone?

To me determining the classified area would be more better served by a chemist as fire and explosions are a chemical reaction that most would not understand such as myself, does a P.E even get this kind of training?

Also many metals mainly oxides are self oxygen suppliers when the metal has reached a temperature over it's combustible level, we find that metals such as iron oxide and magnesium both are just a few that many deal with in the industry that can catch fire and are very hard to put out, while I don't think there is an explosive level in most cases, I have seen fires as a result of hot work being done in areas where the iron dust has collected on beams or other flat surfaces.

We have two plants that remove the iron oxide from the pickeling juice from the steel industry to be used in making magnets and or the iron particles for recording medium, both plants seem to have iron fires at least once a year, but since the fires are in areas that can cause little damage to the building they are in most cases just left to burn themselves out, as far as magnesium goes at an aluminum plant I worked at back in the seventies, we had a pallet of magnesium that was set too close to the scrap remelt furnace that cought fire because of a splash out, the fork lift driver grabed it and dumped it into a cooling pond not far away, and it continued to burn under water, but I have never seen any LEL rateing of metals?
 

GoldDigger

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... but I have never seen any LEL rateing of metals?
That is because LEL by definition only applies to vapors or gasses, in which the material is uniformly mixed in with the air.
For solid particles the explosive mixture is not determined simply by the concentration. It also depends critically on the particle size, since the surface area is more important that the mass.
A room with 5 lbs or coal mixed into the air in the form of charcoal briquets is no hazard. The same room full of very fine dust made from grinding up the charcoal is an explosion hazard. LEL is too simple a ratio measurement to account for that difference.
 

don_resqcapt19

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...
Also what I find strange is very little is mentioned about the temp at which the LEL rating is at, we see Diesel fuel has a LEL of .6 but Gasoline has an LEL of 1.4, but how is this possible without the temperature of the LEL rating also put in to the equation, this part I do not understand?

If we have a fuel that is non-explosive such as Diesel at room temperature, how can it have a lower LEL then gasoline?, is this why we can't use the LEL ratings of the combustible mixture for classification of the zone? ...
The LEL is just the percentage of flammalble vapors in the air. If the liquid product that will give off the flammlable vapors has a temperature too much below the flash point, you will never reach the LEL as there will not be enough vapors given off. I am not sure how much below, before you can have enough flammable vapors to reach the flash point.

...Also many metals mainly oxides are self oxygen suppliers when the metal has reached a temperature over it's combustible level, we find that metals such as iron oxide and magnesium both are just a few that many deal with in the industry that can catch fire and are very hard to put out, while I don't think there is an explosive level in most cases, I have seen fires as a result of hot work being done in areas where the iron dust has collected on beams or other flat surfaces.

We have two plants that remove the iron oxide from the pickeling juice from the steel industry to be used in making magnets and or the iron particles for recording medium, both plants seem to have iron fires at least once a year, but since the fires are in areas that can cause little damage to the building they are in most cases just left to burn themselves out, as far as magnesium goes at an aluminum plant I worked at back in the seventies, we had a pallet of magnesium that was set too close to the scrap remelt furnace that cought fire because of a splash out, the fork lift driver grabed it and dumped it into a cooling pond not far away, and it continued to burn under water, but I have never seen any LEL rateing of metals?
Flammable metals will have an ignition temperature and in the case of powered metals there will be a MEC, (minimum explosive concentration) and a MIE, (minimum ignition energy).
 

Strathead

Senior Member
Actually, when you read NFPA 497 it talks about a multidiscipline team who should determine the area classification by contributing their individual experties necessary for the machinery, materials, mode of operation. Architects would have VERY little to contribute. Process engineer, Operations, Maintenace, Chemical Engineers, Safety Experts and E&I engineers or individuals having expereince and knowledge in those fields should particiapte in the work.
Thank you Lazlo. The classification of areas that are not distinctly designated in the NEC are very hard to nail down. Getting someone to take responsibility is like pulling teeth.
 

Strathead

Senior Member
  • At one time the NEC required Zone classified locations to be done by a PE; the NEC no longer does but FedOHSA still requires it. It can be done by anyone qualified to do so, no matter what the discipline.
  • I definitely consult with other disciplines; but, in the end, it is has always been my name and seal on the electrical area classification drawings.

I have personally experienced two situations where the Electrical Engineer of record passed the buck and wouldn't provide the classification of an area.
 

iceworm

Curmudgeon still using printed IEEE Color Books
Location
North of the 65 parallel
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EE (Field - as little design as possible)
I would agree...having an escape bottle would not be good enough...in my opinion, if you are in a Class I Division 1 area you need to be using PPE suitable for the hazard...not just have it available. In the case of flammable products that may also require PPE to protect you from fire as well as inhalation hazards.
Don -
I think you are stuck in fire-fighter mode. And I highly suspect you don't do work in these areas.

My first questions are:
Q1: What danger of fire?
Q2: What danger of inhalation hazard?

The area is sniffed clear and monitored - remember?

Here is an example: Cutting and welding inside of a tank yard - products with a flashpoint less than 100F. Yes, people actually do this stuff. I picked this one because it's somethng I did in a previous life - so it is not contrived.

Inside the tankyard, below the berm is DIV 1 - as I recall (API RP 500) Now, how do you suspose that one does this with a 1,000,000 gallons of Av-gas or Jet-B staring at you over your shoulder. The ppe consists of treated cotton fire resistant coveralls. Nomex gets ate up from the welding splatter - its useless. There are no escape bottles, or in-use SCBA - that's riduculus. Provided you bothered to read my posts, you already know how one does this safely - with a couple of extras:
Isolate and clean up the piping.
No tank loading while work is on-going - don't want any venting
Post a fire watch - with an extinguisher or two, and a shovel

Now that you are working up a good case of indignant righteousness - I have a couple of questions:
Q3: This ppe that you insist is needed for work in a C1D1 area (non-confined space), just what standard are you using to select the protection level?

Q4: Once a day the company sends the yardman to record the mechanical level gauges. Do you expect her to wear the same gear as the welded plumbers?

ice
 
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