Baffle Design in an API 650 tank

[marcleblanc12]

I need to design a baffle in an API 650 tank. The tank is 47' Dia X 24' High. There is a baffle inside the tank which is 20' high by 38' long welded to the bottom plates and on one side against the inside of the tank shell. The baffle will never hold all the liquid on one side, but will instead make the liquid flow from one side of the tank to the other through the opening between the end of the baffle and the shell.

The question is, how does one go about determining what forces will be acting on this baffle? It will see a hydrostatic pressure as the tank fills, but equal and opposite on both sides.

I have found some methods of calculating baffles in a pressure vessel design handbook, however they are based on the baffle holding liquid on one side of the tank. I could go about it this way, but it would be extremely overkill since this baffle I'm trying to design will not hold liquid to one side, but merely direct the flow from one side to the other as it fills or empties.

Has anyone encountered this before?

Marc

 

[JStephen]

Treat the flow path around the baffle like it was a pipe, calculated pressure loss along the length, and it will give you a (very small) pressure differential across the baffle.

Seismic sloshing is a different issue. It may be reasonable to treat the baffle as expendable in that case.

Note that they do make fabric curtain baffles also.

 

[marcleblanc12]

Interesting notion, I'll give that a try. I do know the maximum filling and emptying rate and I also do have the seismic sloshing values in my tank design calculations.

I'll see what type of results that gives me.

Thanks,

Marc

 

[MJCronin]

Why is the baffle there ? Perhaps I am missing something ....

What is the liquid in the tank ????

MJCronin
Sr. Process Engineer

 

[IFRs]

It sounds like this is a partition that runs across the bottom of the tank and sticks up in the air 20 feet but stops short of the tank shell by 9 feet on one side.

If there is flow perpendicular to the baffle, figure the stagnation pressure and treat it as a cantilevered beam or plate with supports on two sides and some two dimensional pressure gradients.

If the foundation under the bottom is not concrete, there may be forces the plate as it supports the bottom.

 

[MJCronin]

IFR brings up a good point......

Does the tank design include anchor bolts ? Anchor bolts and a concrete ringwall or pad should be included in the design.

There will be unbalanced loads on the anchorage and these should be evaluated by calculation.

MJCronin
Sr. Process Engineer

 

[marcleblanc12]

The liquid in the tank is oily water (S.G.=1.0). There are actually 5 baffle plates in the tank and they don't cross the entire tank. They're all 9' short of the opposite side of the tank shell. Therefore they are never going to contain all the liquid on one side of it. They merely direct the flow in and out.

The inlet and outlet nozzles are parallel to the outer most baffles, therefore they will not spray directly onto the baffle plates.

Yes, the tank is anchored.

From what I can tell the greatest possible force acting on the baffles are the Impulsive and Convective forces due to seismic. Based on my calculations I get an equivalent of 0.45 psi that could potentially act on the baffles. I have a method of calculating the plate thickness, and stiffeners from a pressure vessel design handbook. I'm in the process of designing them now and it looks as though I'll be getting some reasonable results. (not ridiculously overkill)

Feel free to share your thoughts, if you've come across something like this before.