Top Angle Minimum Weld to Shell

[Ganolli]

Hi !

I have several individuals telling me differents things here, and I can't find a clear statement anywhere in the API.

What is the minimum fillet weld I can use when welding a top angle to a shell plate ?

For example here, if I'm using detail b from figure F-2 of the API650, and I have an angle 3x3x3/8 on a 1/2in thick shell.

Thanks guys !

Oli

 

[EISI]

In the past we have always used a full fillet weld. I am curious as to why the top shell course would be 1/2" thick as usually it is only 1/4" as there is virtually no hydrostatic head and a thicker course is not required.

 

[Ganolli]

The tank is 72ft high, it has a C.A., and it must be calculated to sustain wind load in the corroded condition....Things get pretty nasty...

 

[IFRs]

If this is an open top tank with a wind girder a couple of feet down, you don't need the top angle. Otherwise, I'd use 3/8 fillet welds. If you go smaller, you'll have to justify using less and that could get time consuming.

 

[Duwe6]

Use a 'Full Fillet' if the angle is the same thickness as the shell. If the shell is thinner, use a fillets the size of the shell thickness.

Doing this will give more weld strength than the shell strength, so the quantity and strength of weld is unassailable. With fillet welds, sometimes more weld causes problems. When you are as strong as your weakest member, extra weld just wastes time & money, and causes extra distortion.

 

[JStephen]

As best I can tell, this would fall under the minimum fillet requirement of 5.1.3.3.

Note that in figure 5-2, the upper fillet is shown smaller than the thickness of either member.

The required strength could be evaluated based on pressure uplift and will likely produce a very small required fillet in most cases.