Steel Tank Grounding

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FaradayFF

Senior Member
Location
California
Hi guys,

[FONT=Tahoma, Arial, Helvetica, sans-serif]Have you in your practice ever grounded a steel water storage tank? If the steel tank rests on a concrete pad, then the tank is considered grounded by UL 580 standard. I'm not sure how the static electricity is discharged into the ground if the tank is not bonded to ground. I can see how the lightning will be "transferred" into ground if the unit is hit by lightning due to the steel tank acting as a lightning rod and concrete pad acting as Ufer ground.[/FONT]

Thoughts?
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
I know it's not the same thing, but I once wired a cellular site (only the stuff on the ground!) and put in a ground ring cad-welded to rods every 10' (if I remember correctly) with a stub cad-welded to every platform post, power-pedestal post, etc., everything metal nearby.

You could probably do a great job with one rod clamped with a wire bolted to each corner or to be leg. Even that is probably overkill. As you said, you may not need anything. Who is asking for it? What are their expectations? Is there any associated electrical equipment?
 

oldsparky52

Senior Member
In the fuel business, we would install an isolating material between the concrete and the bottom of the tank or the tank manufacturer would coat the bottom of the tank (vertical) or saddles (horizontal) with something that would isolate it from the concrete (corrosion protection).

I had read once (don't remember what publication) that the tanks needed to be grounded at opposite corners of the tank (we mostly used horizontal tanks). I think they were looking for a #8 minimum conductor. I think the tanks now are shipped with ground lugs on them for this purpose.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
I don't think it matters much for static or lightning. Do what is the code minimum or what the customer wants you to do and is willing to pay for and be done with it. I'm not 100% sure but I think the code minimum is nothing.

Lightning is not going to care whether it is grounded or not. If it is sitting on a concrete pad it is highly unlikely you will have any static build up between the concrete pad and the tank. It's not like it would matter any if you had static buildup anyway.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
On industrial sites, at least around her, steel tanks, both indoor and outdoor, are connected to the plant grounding grid at two locations.
 
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