Classified Receptacle

[PapaGreg]

I need to install convenience receptacles on the tops of outdoor grain bins that are fed with a drag conveyor. These receptacles will be near the dust, when the conveyor is in operation. There is a walkway along the conveyor that will connect the bins together. Do these receptacles need to be rated for Class 1 Division 2 Groups E, F, G? These receptacles need to be GFCI protected, also.

 

[GoldDigger]

I need to install convenience receptacles on the tops of outdoor grain bins that are fed with a drag conveyor. These receptacles will be near the dust, when the conveyor is in operation. There is a walkway along the conveyor that will connect the bins together. Do these receptacles need to be rated for Class 1 Division 2 Groups E, F, G?

A couple of thoughts, without the answers:
Can you ever safely plug portable equipment into an already energized receptacle inside a classified area?
To what extent is the open air space adjacent to the conveyor classified? When operating? When not operating?

 

[PapaGreg]

Those are the reasons for the post. Guess I will bite the bullet.

 

[GoldDigger]

Those are the reasons for the post. Guess I will bite the bullet.

Wait awhile for some others to chime in with their answers.....
Another question: What will these convenience receptacles be used for? Or is that unknown?

 

[petersonra]

I need to install convenience receptacles on the tops of outdoor grain bins that are fed with a drag conveyor. These receptacles will be near the dust, when the conveyor is in operation. There is a walkway along the conveyor that will connect the bins together. Do these receptacles need to be rated for Class 1 Division 2 Groups E, F, G? These receptacles need to be GFCI protected, also.

why would they need to be class I if it is a dust issue?

in any case, EFG are class II designations.

It seems to me it is entirely dependent on the area classification.

i don't know much about Class II areas but I am pretty sure the receptacles used won't fit a normal plug like might be found on a typical trouble light or a portable tool.

Grain elevators are scary to me anyway. Glad I don't deal with them.

 

[rbalex]

"Near the dust" is one thing; in the dust is another. Unless the receptacles are "in the dust" there is nothing to consider. You?ll need someone familiar with the process to do the actual electrical area classification; we can?t do it for you here.

As Bob pointed out this is a Class II, Group G application. Group E can only be Division 1, and Group F is basically coal.

The requirements for receptacles in Class II, if necessary, are in Section 502.145.

 

[heavyaslead]

Classification

Classification

Get clarification from the Owner what classification this is. Otherwise a licensed Chemical Engineer is the only truely qualified to classify materials in the area and assertain boundaries.

 

[don_resqcapt19]

Get clarification from the Owner what classification this is. Otherwise a licensed Chemical Engineer is the only truely qualified to classify materials in the area and assertain boundaries.

I don't see how a chemical engineer would be needed to classify a dust hazard area. The classification would be based on how much dust is in the air around the equipment or how much is on the equipment. Seems like a mechanical engineer would be a better choice.

 

[GoldDigger]

Seems like a mechanical engineer would be a better choice.

As long as the MechE consults the MSDS or other references to figure out what concentrations are cause for concern. He may not have it on the top of his head, but he should be able to find the answers. A Civil Engineer, on the other hand..

 

[Strathead]

Get clarification from the Owner what classification this is. Otherwise a licensed Chemical Engineer is the only truely qualified to classify materials in the area and assertain boundaries.

I actually think that classification is ultimately the responsibility of Architects, basically Life Safety plan stuff. I can tell you that getting anyone to really make that determination is like pulling teeth, but no electrician should be willing to do it withe their license. They may depend on information from chemical, electrical mechanical engineers etc.

 

[Strathead]

A couple of thoughts, without the answers:
Can you ever safely plug portable equipment into an already energized receptacle inside a classified area?
To what extent is the open air space adjacent to the conveyor classified? When operating? When not operating?

There are receptacles rated for various classified levels, or more accurately receptacle and plug combinations. Look them up in Appleton or Crouse Hinds. Basically though, the design interrupts voltage to contacts exposed to the environment, and insertion of the plug when completed, (twisting, dropping the cover etc.) makes contact in a confined area isolating the spark.

NFPA publications 497, 499 deal with the guidelines to classify various locations for electrical purposes. Again though, not our job to interpret them. Not a bad idea to have them though, if you are going to do work in these locations often.

 

[GoldDigger]

There are receptacles rated for various classified levels, or more accurately receptacle and plug combinations. Look them up in Appleton or Crouse Hinds. Basically though, the design interrupts voltage to contacts exposed to the environment, and insertion of the plug when completed, (twisting, dropping the cover etc.) makes contact in a confined area isolating the spark.

Because of the requirement for the matching plug on the portable equipment, I would have a hard time calling these "convenience" receptacles. But safe just the same.
Would it be OK to carry around adapter cords so that you could plug the equipment into the adapter and then adapter into the classified receptacle? Or would jus the presence of the normal receptacle on the adapter and tool make use of the adapter prohibited?
I guess that using such an adapter would be OK if the area is not actively dusty at the time of use (that is, conveyor shut down and dust settled.)

 

[Strathead]

Because of the requirement for the matching plug on the portable equipment, I would have a hard time calling these "convenience" receptacles. But safe just the same.
Would it be OK to carry around adapter cords so that you could plug the equipment into the adapter and then adapter into the classified receptacle? Or would jus the presence of the normal receptacle on the adapter and tool make use of the adapter prohibited?
I guess that using such an adapter would be OK if the area is not actively dusty at the time of use (that is, conveyor shut down and dust settled.)

second one, because don't forget, the tool needs to be rated as well. These type areas need to be taken seriously, and the shut down suggestion is the "best" solution, but Doesn't change the overall classification of the area, it establishes safe working procedures. I compare it to a huge fuel tank. You know they often have to weld inside one. Well that is certainly a Class 1 Division 1 area, but not while they are welding. The potential for explosion is what is used to rate an area. That potential can be removed by any of a number of different methods, including, ventilation, barricades, or even removal of oxygen.

 

[weressl]

I actually think that classification is ultimately the responsibility of Architects, basically Life Safety plan stuff. I can tell you that getting anyone to really make that determination is like pulling teeth, but no electrician should be willing to do it withe their license. They may depend on information from chemical, electrical mechanical engineers etc.

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.

 

[iceworm]

Note: Following baised on previous lives working for a general contractor, piping and maintenance, hydrocarbon facilities.

...Would it be OK to carry around adapter cords so that you could plug the equipment into the adapter and then adapter into the classified receptacle?

If you didn't have one, you would be the only maintenance tech (mechanical or electrical) in the area that didn't.

...I guess that using such an adapter would be OK if the area is not actively dusty at the time of use (that is, conveyor shut down and dust settled.)

uhhhh Yeah!

Personal Opinion:
For a tech to perform work in area potentially above the LEL requires equal parts insanity and moron. For a foreman to consider sending a tech into an area potentially above the LEL is worse - total insanity, total moron.

For any work potentially capable of producing a spark of suficient energy to ignite: Get a meter, check %LEL, ventilate till clear, shut down process if needed. No exceptions.

I don't even like the idea of buying copper/berillyum (I'm sure I didn't spell that right) tools. It sends the message that it is okay to do work in an atmosphere above the LEL. It isn't.

So sayeth the worm

 

[kwired]

Considering this is outdoors, one needs to ask if the location is even classified. Part of what makes dust from grain handling explosive is fine airborne combustible particles in an enclosed area. Same particles all settled and out of the air are not much of a threat. Same particles in a non confined area are also not as much of a threat. Outdoors you don't normally get as potent of a concentration and have no walls to contain pressure if combustion should occur. It is the failure of walls to contain the pressure that causes the major disasters in an elevator explosion more so than the combustion itself.

As much grain bin wiring as I have done, I can't recall ever installing classified location methods on anything located outdoors, dust concentration is just not same as it is when enclosed.

 

[don_resqcapt19]

Note: Following baised on previous lives working for a general contractor, piping and maintenance, hydrocarbon facilities.


If you didn't have one, you would be the only maintenance tech (mechanical or electrical) in the area that didn't.


uhhhh Yeah!

Personal Opinion:
For a tech to perform work in area potentially above the LEL requires equal parts insanity and moron. For a foreman to consider sending a tech into an area potentially above the LEL is worse - total insanity, total moron.

For any work potentially capable of producing a spark of suficient energy to ignite: Get a meter, check %LEL, ventilate till clear, shut down process if needed. No exceptions.

I don't even like the idea of buying copper/berillyum (I'm sure I didn't spell that right) tools. It sends the message that it is okay to do work in an atmosphere above the LEL. It isn't.

So sayeth the worm

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.

 

[don_resqcapt19]

Considering this is outdoors, one needs to ask if the location is even classified. Part of what makes dust from grain handling explosive is fine airborne combustible particles in an enclosed area. Same particles all settled and out of the air are not much of a threat. Same particles in a non confined area are also not as much of a threat. Outdoors you don't normally get as potent of a concentration and have no walls to contain pressure if combustion should occur. It is the failure of walls to contain the pressure that causes the major disasters in an elevator explosion more so than the combustion itself.

As much grain bin wiring as I have done, I can't recall ever installing classified location methods on anything located outdoors, dust concentration is just not same as it is when enclosed.

That is a very good point...there are documents that suggest that if you can fully extend your arm and still see your hand, the dust concentration is less that what is required for a fire or explosion.

 

[GoldDigger]

That is a very good point...there are documents that suggest that if you can fully extend your arm and still see your hand, the dust concentration is less that what is required for a fire or explosion.

I would think that might depend pretty heavily on what the dust is and the particle size. Coal dust, grain dust, aluminum dust, magnesium dust.

 

[kwired]

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.

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

That is a very good point...there are documents that suggest that if you can fully extend your arm and still see your hand, the dust concentration is less that what is required for a fire or explosion.

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.