Welding Tanks to Foundation

[cwigg66]

I recently inspected three fuel storage ASTs in Florida, and found that all three tanks were welded to their foundation. That is, the concrete pedestal on which they stood had steel plates (probably small I beam pieces) cast into it, and the tanks were welded to those plates directly. Has anyone ever seen this, and wouldn't it be better to weld tabs to the tanks and bolt them down that way. The welded areas were poorly coated due to clearance issues and had already begun to corrode after only two months of service.

If anyone can point me in the right direction as to what Florida regulation requires tanks to be anchored, it would be helpful.

FYI, the tanks are 30K vertical tanks, covered with a metal pole barn, and surrounded with a concrete containment structure. Tanks are UL rated. Thanks

Chris

 

[TankDude]

I have seen this in the past. Typically the embedded members are channel (or I beam possibly). The arrangement that I have seen in the past had only the tank shell welded to the member with no steel bottom. I honestly couldn't tell you the advantages/disadvantages, aside from possibly avoiding prolonged concern with bottom corrosion. Depending upon where in Florida this could be a major concern due to the salt in the air. This connection does obviously help to resist uplift and sliding, however the welded area must be properly designed. As for a Florida regulation for anchoring, I don't know of one specifically. I always reference API 650 which not referes to the ASCE 7 (and subsequently the IBC).

 

[JStephen]

I'm not sure if you are talking about the same things. TankDude, you're thinking of a tank with embedded channel, continous around the tank, but with no floor? I've seen this done with water tanks, but never with a fuel tank of any kind. And Chris, sounds like your tank has a regular steel floor, and it is just welded to bits of steel that are embedded in the foundation?

I can see corrosion being a problem here. This seems like a week connection, as it seems the uplift force could bend the tank bottom chime down. The only way I can see this working would be if uplift forces were very minimal- which is what you have with a 30,000 gallon tank.

Generally, I think building codes would require construction per the tank codes. For a UL tank, you'd need to refer to the UL standards to see if that is permitted. I don't think it would meet API-650.