Structure Design For Spherical LPG Tank

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=5&cad=rja&uact=8&ved=0CFEQFjAE&url=https%3A%2F%2Flaw.resource.org%2Fpub%2Fus%2Fcfr%2Fibr%2F002%2Fapi.2510.2001.pdf&ei=XpE9U96iN6iysASV_4GYCg&usg=AFQjCNFBpKsaTnMKOXbJNrhBqLxFLDSYww&sig2=oeTJPXAdhzzh9zv-vMlUoQ&bvm=bv.63934634,d.cWc

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http://www.gobookee.org/structural-details-of-spherical-lpg-tanks/

Thank you for the documents, but all of these publications are design recommendations.

I really need a detailed procedure to design the columns and the cross-bracing ( Thickness, diameter, cross bracing angle ...). Or since the weight depends on the pressure would it be adequate to use the suggested sizes given in the table 6-26 "Dennis R. Moss" (50psig sphere) that match with my sphere's weight ?

Thanks for your help

The support structure doesn't depend on the tank pressure; it depends on the tank weight.

Filled Tank "full" weight LPG included.

In fact since the weight depends on pressure the structure depends implicitly on pressure.

The weight of the gas above the liquid depends on its pressure, but I don't think the weight of the liquid varies much with its pressure. In any event, a full tank should already assume the worst (heaviest) case (coldest temperature).

In what way? The LPG is liquid at operating pressure, SG about 0.6, but OP should check. To give a bit of safety I would design for vessel full of liquid (in practice there is a gas space at the top).

...except don't use LPG as the design fluid as far as the gross weight is concerned. From time to time the vessel will need to be full of a denser liquid for test purposes. So for a vessel designed to hold a liquid of SG <1, an SG of 1 for the test fluid, i.e. water, would be a requirement for the support structure and its foundations so that the vessel can be hydraulically tested in-situ for time to time for burst and collapse indemnity insurance purposes.

The support design should also allow for the bund being full of rainwater and there being no tendency for the empty vessel to behave like either a boat or a submarine.

Some Concrete Muncher somewhere should be on with the foundation and bund design while the Original Poster is doing the vessel design. One hopes that these two are working together...

OK, fair point about hydro-test fluid SG. Not sure about flotation risk though. I thought LPG tanks weren't put in bunds, due to risk of heavier-than-air gas accumulating, but I could be wrong. I've seen plenty of them above ground.

Noted. If there's no bund then the boat/submarine consideration need not apply. That is where the Concrete Muncher Civils Designer comes in.

Is your design pressure really 40 barg ? (~580 psig)

If so, you may be designing one of the highest pressure, large spherical tanks in the world. This may be part of your problem..... you may have been assigned to design a vessel with an excessively high design pressure.....by mistake.

This is why the Moss book uses the 50 psig design temperature in the design example...... because it is customary for many liquids and reasonable.

What liquid on earth requires this extreme pressure ?

How was this decided ? What is the reasonable "maximum operating pressure" for this particular facility?

Was this pressure given to you by an MBA ?..... perhaps a marketing major ?

The pressure at refill stations is MUCH MUCH higher (up to 5000 psi which means about 350 barg!)but they use bottles. May be one wants to have a spherical reservoir.