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Stainless storage tank fabrication

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Ivan Silva

Industrial
Dec 13, 2019
45
BR
I recently was moved on to a project which demands to reverse engineering an tank in order to fabricate another equal ones. Until now I had only worked with automation machines so I’m quite inexperience with tank fabrication so I have some question about it.

The tank main body has 700 mm external diameter and 2 mm stainless steel thickness. In its top there is an 760 mm external diameter flange weld on it. About this flange what’s the common way of locating in the tank? I mean the flange internal diameter must be larger than the tank external diameter in way the main body fits inside the flange? Like in tube and flat flanges fittings?

Considering the flange is a flat bar which will rolled round and welded closed does the process of rolling guarantee certain level of roundess to the internal and external diameter or normally after the roll process the flange is turned in lathe to properly set the internal and external diameter?

Another question the flange has 16 holes in it. Normally does this holes are drilled before the roll process (when the flange is flat bar) or after it was rolled?

 
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There are standards and standard details for large tanks as commonly used for water storage, petroleum storage, etc. I am not aware of any such standard for small tanks like this.
On the flange- I would expect either a corner-to-corner weld or the tank body inserted partway through the flange. If the fabricator had the equipment to do it, the flange could have a lip butted onto the body, or could be formed from the body.
I would expect the flange to be rolled to radius, or cut in one or more pieces from plate, and not turned on a lathe. As-fabricated roundness might not be perfect, but the cylinder it fits on won't be perfect, either.
I would expect holes to be drilled after forming, if rolled from bar. Normally, the two pieces would be clamped or tacked together and drilled together. If layout was by hand, it may not be possible to rotate the flange and still bolt it up.
I would say on each of these issues, it would be more important to fabricate something workable for you rather than trying to match the existing construction.
Talking to a fabricator that routinely does this type of work would be informative.
One big item is to confirm what kind of finish is needed on all surfaces and on welds, whether polished or what.
Confirm if the tank is or can be pressurized.
If this is for food products, that is kind of a specialty field, so look for someone normally doing that.
 
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