API 620 internal structure design
API 620 internal structure design
(OP)
Hello,
I'm designing a cylindrical tank using API 620, 96ft diameter, conical roof, 15 psig. The required thickness of the roof based on internal pressure (15 psig) is unreasonable ~ 7in.
How can I design internal structure (rafter, girders, columns ..) to reduce the thickness of the plates?
Thanks
I'm designing a cylindrical tank using API 620, 96ft diameter, conical roof, 15 psig. The required thickness of the roof based on internal pressure (15 psig) is unreasonable ~ 7in.
How can I design internal structure (rafter, girders, columns ..) to reduce the thickness of the plates?
Thanks





RE: API 620 internal structure design
I recommend using a dome roof with a hefty compression member. The best bet is to contract with an experienced tank builder and let them perform the design work. It is quite easy to make large, expensive mistakes while working on large API 620 tanks.
RE: API 620 internal structure design
Do you know of any reference books for designing internal structure in API 620?
Thanks
RE: API 620 internal structure design
RE: API 620 internal structure design
You can reduce cone roof thickness by increasing the slope, using higher-strength material, using higher joint efficiency, using less corrosion allowance, or reducing the pressure.
A cone roof that size would normally have supporting structure below it as well.
Another potential problem will be the anchor bolts and foundation size required to anchor that uplift force.
RE: API 620 internal structure design
If EngFax is set on cylindrical tanks, a larger number of smaller diameter tanks would be a much easier proposition.
RE: API 620 internal structure design
With the volume you seem to desire and the 15 psig design pressure, you are beyond the reasonable range for a flat bottomed tank design, in my opinion.
Yes, I realize that API-620 designs go nearly to this limit, but it is not always wise to choose this type of design.
I believe that your 15 psig design pressure may be an arbitrary choice and not indicative of the liquid's true vapor pressure..... you should press the process engineer on this because it has such a large effect on your design.
Ask experienced API-620 design firms what their dimensional/pressure limits are for their tanks.
A better and cheaper choice may be a series of horizontal "bullet" tanks, designed to ASME-VIII
What is the stored liquid and what is the design temperature ?
What is the total volume ?
RE: API 620 internal structure design
The liquid stored is Raw Methanol, 150 F. I'll go with you guys suggestion (multiple small tanks). But do you know of any firm that design according to API-620 or any calculations example of a API-620 tank.
RE: API 620 internal structure design