Puzzling Scenario

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AdamLandry

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Lake Charles, La, USA
I had a question presented to me today that really stumped me, so I am wondering if anyone has come across this and would know the nature of this phenomenon.

About twenty-eight years ago an electrician drove a copper ground rod at a 600A 120/240 single phase service servicing multiple structures on the property. The service was placed within a structure specifically for the electrical gear and other components for the facility's phone lines. The GEC was located in the MDP and was attached to one ground rod that had approximately 6" above the ground. The acorn was located at the very top of the rod.

It was explained to me that approximately five years after the rod was driven he was called back by the owner. Approximately 3" from the acorn and 2" from the ground the rod had broken off. He expressed that the rod was in a cone type shape at the location where it had broken off.

He drove another copper rod, and approximately five years after he was called back again. The exact same phenomenon had occurred. He attempted to figure out why this was taking place but could not get any answers. He was advised to drive multiple ground rods around the small structure housing the equipment, but with no real explanation why. He drove 5 ground rods and connected them. To this day there have been no issues of this sort with the facility.

Can anyone give me a physical, chemical, electromagnetic reason why or how this would/could occur? I don't have any reason to believe that this individual is being dishonest with his inquiry. I have just exhausted my mental resources with the situation and am wondering if any of you have some thoughts regarding this.
 
AdamLandry said:
I had a question presented to me today that really stumped me, so I am wondering if anyone has come across this and would know the nature of this phenomenon.

About twenty-eight years ago an electrician drove a copper ground rod at a 600A 120/240 single phase service servicing multiple structures on the property. The service was placed within a structure specifically for the electrical gear and other components for the facility's phone lines. The GEC was located in the MDP and was attached to one ground rod that had approximately 6" above the ground. The acorn was located at the very top of the rod.

It was explained to me that approximately five years after the rod was driven he was called back by the owner. Approximately 3" from the acorn and 2" from the ground the rod had broken off. He expressed that the rod was in a cone type shape at the location where it had broken off.

He drove another copper rod, and approximately five years after he was called back again. The exact same phenomenon had occurred. He attempted to figure out why this was taking place but could not get any answers. He was advised to drive multiple ground rods around the small structure housing the equipment, but with no real explanation why. He drove 5 ground rods and connected them. To this day there have been no issues of this sort with the facility.

Can anyone give me a physical, chemical, electromagnetic reason why or how this would/could occur? I don't have any reason to believe that this individual is being dishonest with his inquiry. I have just exhausted my mental resources with the situation and am wondering if any of you have some thoughts regarding this.
Click to expand...

Unrelated and not what you asked but if there is high current flow over copper water pipes, you could see green water when flushing the toilets. Seen this with misplaced neutral currents on the grounding water pipe paths.

Also dissimilar metal types in contact, in the presence of water, will cause galvanic action and the plating of one metal onto the other.

Some mineral or salt contents in drinking water can cause accelerated corrosion of the metal piping.

Never seen anything that could sever a ground rod, which are typically copper plated steel.

However, what to look for is certainly in view. Possible causes would be unusually corrosive minerals or salts in the surrounding soil and current flow over the ground rod caused by multiple (more than one) neutral to ground system bonding jumper connections.

The supply transformer would have only one neutral to ground system bonding jumper connection. If the surrounding powered structures also have a neutral to ground connection on the same supply transformer, there would be the possibility of some neutral current flow occurring over the paralleled earth path, down one ground rod and up the other, accelerating any corrosion caused by aggressive soil types.

Amp clamping the grounding electrode conductors and looking for stray neutral current would be the first step. If that's clean, next step would be installing an electrode system that can withstand the locally occurring aggressive corrosive action (which you state has been done).
 
FWIW, corrosion of that extreme sort is more usually associated with DC than AC voltages.
Some non-linear loads or really odd soil chemistry might be causing a DC voltage offset between the driven ground rod and remote earth.

Do not be satisfied looking only for AC voltage offsets or AC current in the Ground Electrode System (GES).
If there is municipal water or gas, they may deliberately put a DC voltage (small DC current) on their pipes to protect them from corrosion and the ground rod would be left with the short end of the stick.
 
Sounds like really nasty beavers:D

Seriously - 2-3 inches above grade, sounds like lawn mower maybe could be rubbing against it, removing the copper cladding therefore exposing the steel which will corrode faster then the copper will. (rods typically are steel rods with copper cladding on them, pure copper rods would be too soft to drive into most soils)

Why not drive rods below grade in the first place?
 
kwired said:
Sounds like really nasty beavers:D

Seriously - 2-3 inches above grade, sounds like lawn mower maybe could be rubbing against it, removing the copper cladding therefore exposing the steel which will corrode faster then the copper will. (rods typically are steel rods with copper cladding on them, pure copper rods would be too soft to drive into most soils)

Why not drive rods below grade in the first place?
Click to expand...

Driving rods below grade is common practice now. As early as 7-10 years ago it was not, and still is a problem we are daily trying to address with the "this is always how we've done it" mindset.

I was thinking along the same lines but with a weedeater/trimmer. I thought that perhaps the continued whipping of the cutting string could potentially expose the inner steel core. My only dilemma with this line of thought was the coning effect. Couldn't fully explain that aspect of the situation.


Sent from my iPhone using Tapatalk
 
AdamLandry said:
Driving rods below grade is common practice now. As early as 7-10 years ago it was not, and still is a problem we are daily trying to address with the "this is always how we've done it" mindset.

I was thinking along the same lines but with a weedeater/trimmer. I thought that perhaps the continued whipping of the cutting string could potentially expose the inner steel core. My only dilemma with this line of thought was the coning effect. Couldn't fully explain that aspect of the situation.


Sent from my iPhone using Tapatalk
Click to expand...
Repeated removal of surface rust at about the same position would make it get narrower in that position over time.
 
GoldDigger said:
FWIW, corrosion of that extreme sort is more usually associated with DC than AC voltages.
Some non-linear loads or really odd soil chemistry might be causing a DC voltage offset between the driven ground rod and remote earth.

Do not be satisfied looking only for AC voltage offsets or AC current in the Ground Electrode System (GES).
If there is municipal water or gas, they may deliberately put a DC voltage (small DC current) on their pipes to protect them from corrosion and the ground rod would be left with the short end of the stick.
Click to expand...

Why would DC voltage from the gas/water company not do harm on their system but a DC on the ground rod will?
 
edward said:
Why would DC voltage from the gas/water company not do harm on their system but a DC on the ground rod will?
Click to expand...

They design the protective system to suit the needs of what is being protected vs just putting random voltage on the item being protected. Polarity might be reversed in some applications vs others, sacrificial anodes might be used...
 
AdamLandry said:
I had a question presented to me today that really stumped me, so I am wondering if anyone has come across this and would know the nature of this phenomenon.

About twenty-eight years ago an electrician drove a copper ground rod at a 600A 120/240 single phase service servicing multiple structures on the property.
Click to expand...
Copper or copper clad steel?
 
Was the rod located in an area where a pdfle would form?
standing water a few inches deep?
a low spot/depression?

the other rods may do the same
but since you have 5 may take 5 times as long, 25 years, lol
 
It would be nice if we had a picture but since this was so long ago I can understand why. I'm still not clear on the exact shape of the damage other than it was cone shaped- like this =><= ? Since in both cases it was 5 inches above the soil the only logical conclusion is mechanical damage, maybe even intentional.

-Hal
 
My theory:
A dog is repeatedly lifting his leg on that ground rod, they like to keep re-marking their favorite spots. Left uncleaned, the resultant ammonia is removing the oxide layer on the copper cladding, which is what protects it from the elements. Once that happens, time, rain, pollution etc. corrode away the copper, then the steel beneath it, which corrodes much faster, forming the cone shape.
 
Install a test well around the rod, flush with finished grade, rod driven below grade, to eliminate the weed whip factor. Is this a farm or similar type facility?
 
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