Vacuum Rating of Atmospheric Storage Tanks 1

[UKCats]

I have an atmospheric storage (actually 20 in w.c.) tank with a flat bottom, 2:12 cone roof. It's not built to API 650 but looks a lot like one. I was wondering how high of vacuum rating it could take.

API 650 specifically says limit the tank to 1-inch w.c. external pressure.

FM Loss Prevention Bulletin No. 13.23 says 1 3/4-inch w.c. vacuum for roofs having at least 3/16-inch roofs.

Are there any other industry guidelines w/o perform a rigorous calculation???

 

[KennyRay]

API 650 is generally recognized as the reference code for flat bottom cone roofed tanks. You can analyze all elements using Compress or some other engineering design program. I would be very careful about making vacuum assumptions particularly for an API tank. I have been in the tank and vessel business for 30+ years. During that time I have seen few failures due to pressure but many due to vacuum.

 

[aybee]

the cute answer is ..not much, These are large thin walled pressure vessels and are not designed to take external pressure like Kennyrae said, lots of tanks get collapsed due to vacuum not many blow up

 

[MrVessels]

Depending on your diameter to thickness ratio there are two ASME Code cases that might be of assistance to you.
Code Case 2286-1 (ASME VIII Div 1 and Div 2) or
Code Case N-284-1 (ASME III Div 1)

Both of these limit the D/t ratio to 2000:1 with the nuclear case also limiting the minimum thickness to 1/4".

Caution should still be applied, especially when dealing with existing tanks since deviations from true circular form are generally the cause of vacuum type failures.