Rating Day Tank w/ Stiffeners and conical bottom

[stuarbc]

I have been asked to calculate the ratings (internal and external pressure) of two existing, UNSTAMPED day tanks.

I am trying to figure out which code to apply...but the tanks do not seem to fit any of them

they are small 100 gallon vessels....lug supported....have a conical bottom....welded plate top...supported by lugs welded to the vessel....and there are stiffener rings on the shell. There are actually 3 stiffener rings around the shell and then they are all connected on either side of the tank by a longitudinal stiffener.

oh and they are not atmospheric. At this point I do not know the pressure but they have conservation vents.

Everything in my gut tells me that I am going to have to analyze the vessel per ASME Section VIII Div 1

 

[JStephen]

You can only do that in an approximate sense. Either the tank codes or the ASME code give design rules, and you can work back through those to come up with some rating. But they also specify materials and welding details, and if you don't know the materials, have no information on the welding, etc., then you can't really say they meet those standards, either.

 

[MJCronin]

Stu....

This is a dangerous business that you are in...

I suggest that; despite whatever pressure that you calculate you should consider testing these unstamped vessels. (Can you test a few to destruction ?)

For smaller diameters, (say ...less than 48 inches) I would expect to see positive 3-8 psig as being reasonable.

(The deflection of the flat top head will probably control this)

For external pressures.....good luck perhaps minus 5-10 IWG.

Stand back.... be careful

-MJC

 

[stuarbc]

These are extemelly small pressures we are working with. I have decided to input the vessel parameters into PV elite. Even though the vessel is not an ASME vessel and would not pass all the requirements of an ASME Section VIII vessel....I can still analyze it's components per that code.

In other words, I can input the existing vessel parameters and it will tell me the allowable pressures.....although it will warn me that it is out of compliance with the code.