static grounds

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mickeyrench

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When a flamable cabinet has to be grounded that contains solvents , paint , alchols, at a commercial business is this to prevent static electricity ? Can this be done by connecting the cabinet to the I beams in the building?
 
mickeyrench said:
When a flamable cabinet has to be grounded that contains solvents , paint , alchols, at a commercial business is this to prevent static electricity ? Can this be done by connecting the cabinet to the I beams in the building?
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Yes it's to discharge static electricity. Bond the cabinets to the steel
or cold water pipe.
 
brian john said:
If you know the steel is grounded.
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That is a good point. I know that the steel of all the buildings I
service are bonded. It is a habit of mine to check the bonding jumpers
cold water,building steel, ufer, etc. everytime I enter a main electrical
room,yes I'm a geek .

This leads me to a question. If Table 110.26 (A) (1) Condition 2 says that
"Concrete,brick,or tile walls shall be considered as grounded."
Why wouldn't a steel structure attached to concrete in multiple
locations be automatically be "Considered grounded" without a
bonding jumper? This is purely a hypothetical question.
Concrete walls are typically part of a concrete foundation.
Steel structural beams are typically attached to the footings
of a concrete foundation.
 
Karl H said:
This leads me to a question. If Table 110.26 (A) (1) Condition 2 says that
"Concrete,brick,or tile walls shall be considered as grounded."
Why wouldn't a steel structure attached to concrete in multiple
locations be automatically be "Considered grounded" without a
bonding jumper? This is purely a hypothetical question.
Concrete walls are typically part of a concrete foundation.
Steel structural beams are typically attached to the footings
of a concrete foundation.
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Because Concrete, Brick or Tile Walls are not in 250.52(A)(1)-(A)(7) as suitable for GECs. ;)
 
I have never understood the technical reason for bonding the storage cabinet. I don't see how that makes any difference. The static spark would be between the items stored with in the storage cabinet and the cabinet itself. The only bond that will prevent that spark would be between the internal containers and the cabinet would be one that connects those two items. I don't see any purpose to bonding the cabinet to earth.
 
don_resqcapt19 said:
I have never understood the technical reason for bonding the storage cabinet. I don't see how that makes any difference. The static spark would be between the items stored with in the storage cabinet and the cabinet itself. The only bond that will prevent that spark would be between the internal containers and the cabinet would be one that connects those two items. I don't see any purpose to bonding the cabinet to earth.
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What about the person opening the cabinet? The cabinet can contain
flamable vapors.
 
Karl H said:
What about the person opening the cabinet? The cabinet can contain
flamable vapors.
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Sure it can, but I don't see how bonding the cabinet changes that or reduces the possibility of a spark between the person and the cabinet.
 
don_resqcapt19 said:
Sure it can, but I don't see how bonding the cabinet changes that or reduces the possibility of a spark between the person and the cabinet.
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I have an idea or ideas to answer your question but, I cannot back it up
with scientific facts either. I want to compare an object in a conditioned
space and how would it hold a charge with a refference to Earth,then I think of a tree in contact with Earth and steadily holding a charge. So ,for the time
being, I'm forced to "Punt". I will do more research and address this in
the second half. Maybe the only true way to isolate a flammable cabinet from static
is to not connect it to Earth ,but to put a humidifier in the room that contains
a flammable cabinet.
 
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If the cabinet is grounded, then you dis-charge yourself when you touch the cabinet's handle when opening the door.
 
Speedskater said:
If the cabinet is grounded, then you dis-charge yourself when you touch the cabinet's handle when opening the door.
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Even if it is not grounded you equalize the charge between yourself and the cabinet when you touch the cabinet and eliminate the spark from occurring after you open the door.
 
From Laboratory Safety Fact Sheet Flammable and Combustible Liquid
Storage and Dispensing.
.

Grounding eliminates the difference in static potential charge
between the conductive object and ground. Grounding is accomplished
by connecting the conductive object directly to the earth,usually
using cold water pipes,building steel or grounding bus/bar.

The flow of flammable and combustible liquids can cause the build up
of static electricity. When enough of a charge is built up a spark
can result and potentially cause a fire or explosion. The likelihood
of this happening is dependent upon how well the liquid conducts
electricity, the flash point and the capacity to generate static
electricity.

Static electricity can be generated when liquid is transferred from one
metal container to another. Liquids have the ability to generate static
electricity when they move in contact with other materials during
pouring,pumping or agitating. The build up of this static electricity
can cause a spark to form where the solvent exits the container.
This could result in a fire or explosion.
 
Karl,
I see nothing there that tells me that the bonding the cabinet will really accomplish anything. Even if the cabinet has a charge above earth how does that create an ignition source inside of the cabinet?

I fully agree that bonding between containers when transferring liquids is important and effective.
 
don_resqcapt19 said:
Karl,
I see nothing there that tells me that the bonding the cabinet will really accomplish anything. Even if the cabinet has a charge above earth how does that create an ignition source inside of the cabinet?

I fully agree that bonding between containers when transferring liquids is important and effective.
Click to expand...

I'm sorry to answer a question with a question. Why then,do
the manufactures,OSHA,and NFPA require it? I've bonded at least
50 flammable cabinets and every one of them had an external
bonding lug or tap for a bond from the manufacture.
 
Karl H said:
I'm sorry to answer a question with a question. Why then,do
the manufactures,OSHA,and NFPA require it? I've bonded at least
50 flammable cabinets and every one of them had an external
bonding lug or tap for a bond from the manufacture.
Click to expand...
I have no idea why, and there may or may not be a technical reason that supports this rule. If there is a technical reason I would like to know it.
It seems with a lot of grounding and bonding things there is no real technical reason behind the rule. I expect in many cases the rules were made by people or groups that do not understand the physics of the installation.
 
don_resqcapt19 said:
Even if it is not grounded you equalize the charge between yourself and the cabinet when you touch the cabinet and eliminate the spark from occurring after you open the door.
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This may not be helpful but I think of it like creating an equipotential plane.

If the cabinet is not grounded (and isolated) then when you touch it you equilize the charge between yourself and the cabinet, but not ground.

Thus it is still possible for a spark to occur between either you or the cabinet and ground?

When the cabinet is grounded and you touch it , now all three are at the same potential.
 
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