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variable design point method API 650
2

variable design point method API 650

variable design point method API 650

(OP)
Hello,

i am struggling with the thickness calculation using the variable design point method according to API 650, could any one supply me with a monogram or any application of the method, it would be very helpful.


thank you in advance

RE: variable design point method API 650

It is not really that hard but it is an iterative calculation that usually converges on a thickness in 3 or 4 iterations. You will not find a chart, curve or other simple visualization because there are an infinite number of tank diameters, heights, liquid densities, corrosion allowances, etc. Software is not likely to be given away. Put it in MathCAD if you can, or possibly Excel, etc.

RE: variable design point method API 650

(OP)
thank you IFRs for your reply, that was very informative.

RE: variable design point method API 650

(OP)
here are my questions :

-the calculation of both design and hydrostatic test cases,are the two cases done independently for all the courses of the shell or should they be done simultaniously ?

- i could use some insights as far as the design liquid level is concerned ; does is include the hight of the tank bottom in fixed roof tanks with no overflow ?

- the tank nominal diameter; does it depend on the configuration used for the assambly of shell courses ? (two configuration are available)

RE: variable design point method API 650

alienitmeca,

- Both the hydrostatic and design test cases must be satisfied. My recommendation is to run the thickness calculations in an automated or semi-automated application as IFRs has mentioned for each case. Once you have the process in place, the second calculation should not take much additional time.

- The shell thicknesses are affected only very slightly if you calculate using the inside diamter, outside diameter, or centerline diameter of the shell plates. Your tank is likely large to use the variable design point method, and the shell plate thicknesses are tiny in comparison.

RE: variable design point method API 650

See 5.6.3.2 in API 650 for a discussion of the design liquid level.
You must run independent calculations for both hydrotest and product since the allowable stresses are different, the densities are often different and the corrosion allowances are different for the two cases.
The default for API 650 is that the shell stack plates are stacked with a common centerline 5.1.5.3.b
The default for API 650 is that the tank nominal diameter is the centerline of the bottom ring 5.6.1.1 note 1

RE: variable design point method API 650

(OP)
thank you IFRs and fegenbush ,

that was the answer i was looking for

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