Dear Sir,

AS you know, While calculating the shell thicknesses,we need H Value which is Design liquid level. I believe this value is equal to the value of Total Height of shell in your software.

But in API 650 5.6.3.2, it is written:
" height from the bottom of the course under consideration to the top of the shell including the top angle, if any; to the
bottom of any overflow that limits the tank filling height; or to any other level specified by the Purchaser, restricted
by an internal floating roof, or controlled to allow for seismic wave action,

Please confirm that Tank Software is using H value of TOTAL SHELL HEIGHT not High Operation Level.

Regards.

"H" is the liquid level. If you want to take it to the top of the shell, then input the shell height. This is an input value, you control the value here.

I would add that API 650 says in 7.3.5 "Testing of the Shell"

"If water is available for testing the shell, the tank shall be filled with water as follows:
(1) to the maximum design liquid level, H;
(2) for a tank with a tight roof, to 50 mm (2 in.) above the weld connecting the roof plate or compression bar to the top angle or shell;
(3) to a level lower than that specified in Subitem 1 or 2 when restricted by overflows, an internal floating roof, or other freeboard by agreement between the Purchaser and the Manufacturer,
or
4) to a level of seawater producing a bottom of shell hoop stress equal to that produced by a full-height fresh water test."

IMO, this means also the test level can be different from design level.
Also IMO, strictly speaking, this isn't in harmony with 5.6.3.2 where both design shell thickness and the hydrostatic test shell thickness are required to be calculated based on the same H= design liquid level.

In case Appendix F is applicable, see also F.4.4 "When the entire tank is completed, it shall be filled with water to the top angle or the design liquid level, and the design internal air pressure shall be applied to the enclosed space above the water level and held for 15 minutes. [...]".

I guess API 650 would define more accurate "product design level" and "hydrotest level" as two notions that must be separately evaluated together with Purchaser.

However, for both cases (design for product and hydrotest) is clear there is no requirement to consider H as the top shell, even this is a common practice for "hydrotest".

Dear Richard,

I believe I couldnt explain what I really want. In Tank Software:

there are two kind of Height as inputs. 1 for Height of Shell, 1 for design liquid level. You have to enter these two inputs. But for calculations of thicknesses of shell, which height does TANK use ?

I believe software uses total height of shell, not design liquid level.So thicknesses will be bigger.

I would appreciate if you can clarify this issue.

Regards.

No, it uses the height of the liquid (assuming that was defined correctly in the input).

I think more clarity would prevail if the following heights were considered:

1) Shell Height for metal weight computations.
2) Design height which could be Shell Height if specified by Purchaser/Consultant or some other height depending upon position of overflow nozzle; IFR or sloshing requirements etc. for thickness calculations.
3) Product fill height for wind/Seismic calculations.


Regards,

LINUS