Density in API620/API650

[lucie]

When the liquid stored has a lower density than water, must the tank be designed with the density of water in API620?

In API650 ther is no doubt as two thicknesses are calculated, one with density of fluid (design) and another with density of water (hydrostatic test), and your select the higher of them.

But in API620 you only calculate one thickness and I don`t know if it must be done with the density of liquid to be stored or with the density of water.

Thanks

 

[JStephen]

See section 5.3. Sounds like in most cases, it would be the product head, but with not less than 48 PCF figured for product.

 

[EGT01]

Just so I understand...

it seems that API 650 3.2.1 defines the Stored liquid load and Hydrostatic test load as that determined by filling to the (same) design liquid level. Then by API 650 3.6.1.1, the required shell thickness would be the greater of that determined for either case.

But isn't API 620 5.3.1.2 saying the same thing?... the tank must be designed for both maximum liquid-level conditions (operating and hydrostatic test).

 

[JStephen]

I think 5.3.1.2 is only saying that about tanks designed for liquid to the top of the roof, which is not the general case.