FLAT BOTTOM IN ASME TANK

[jor1492]

Hello, I have to design a storage tank using the ASME code with pressure=30psi , diam=6.3 meter and the bottom have to be flat supported on the ground.

Using the formula for flat covers in the ASME, the thickness is 3.75".

Is this thick usual for tanks of this dimensions or is too much?

What recommendations can you give me for the design of the flat floor for a Tank with these features?

 

[bimr]

No, it will not work. That size of a tank would also have to be field erected.

You need to rethink you tank configuration.

 

[JStephen]

There's no reason a pressure vessel couldn't be designed and constructed with a flat bottom supported by soil. However, ASME simply doesn't address this type of construction, so you're left with the result you're seeing.

This type of construction is covered by API-620 up to 15 psi pressure. Note that at higher pressures, the anchorage and foundation details can become unreasonable as well.

 

[jor1492]

thanks bimr, I 'll talk to the manager of the basic engineering to check the configuration.

Thanks JStephen, then in this case Could I design the foundation to support stresses by the pressure and thus I reduce the thickness of the flat bottom? or What other advice would you give me ?

 

[JStephen]

If the 30 psi/ASME is a requirement, use an F&D bottom head and skirt support.

 

[bimr]

The foundation will basically support the filled dead weight of the vessel. The dead weight will depend on the height of the vessel. The skirt will tranfer the weight of the tank to the foundation.

The thickness of the bottom head will be less because the dished shape is stronger. The design of the tank foundation is independent of the tank design. A tank of this type will have an octagon foundation, maybe 2-3' thick.

The proposed flanged head diameter is close to the largest diameter that is normally manufactured. It will be difficult to ship.

 

[jor1492]

Tanks you for the tips.

I am going to check if I can change the configuration to a Dished shape head with skirt support.

Another question about this tank using the ASME VIII code:
Do you know a way of design a conical head with the half of the apex angle greater than 30 ° without the use of a toriconical head ? Or Any advice for this situation

Thanks in advance

 

[bimr]

No, can't[highlight #FCE94F][/highlight] help with that.

 

[fegenbush]

I responded to your other post on the same topic. UG-32(g) references 1-5 (in Mandatory Appendix 1) for the design of the transition region either with or without stiffening rings. Hint: for a tank this diameter, you will require a stiffening ring.