API 12F Skirted Cone Bottom Tanks 1

[merton]

The API 12F specification references skirted and non-skirted cone bottom tanks. My interest is in the skirted style, but the specification does not provide information on how to design this the components of this assembly. I have a tank design program at work which includes cone bottom design for API 650 tanks, but only for non-skirted applications.

I checked briefly in the Pressure Vessel Handbook as well, but the angle range of the cone (normally 4:12 slope) is to large for the provided calculations for thickness and compression rings.

If anyone could point me in the right direction it would be greatly appreciated.

Thanks

 

[khardy]

Cone bottoms, on legs or skirts, are not covered by API-650. You can use API-620.

For a generalized design procedure I can recommend: “Design of Steel Bins for Storage of Bulk Solids” by Edwin H Gaylord & Charles N Gaylord. (This covers silos for dry products but the stresses in the plate elements are similar.)

 

[merton]

khardy, thanks for the reference text.

If possible, could you specify what part of API 620 in particular would provide design parameters for the skirted cone bottom?

Thank again

 

[khardy]

API-620 section 5.10 for a start. Then 5.12 for the junction and compression ring.

If you are looking for a specific, step-by-step, procedure for designing a cone bottom on a skirt you won’t find it in API-620. Like many codes, the code assumes the engineer already knows how to determine the relevant stress and provides guidance on what stresses are allowed for various conditions. The code is very “general” so it can be applied to a wide variety of scenarios.

Are you going to fabricate this tank or send it out to quote after you design it? If you are going to send it out for quote don’t bother designing it; let the tank fabricator do that. Any reputable tank company will be well versed in the procedures and relevant codes. You just need to specify the overall dimensions, capacity, process connections, etc….

 

[JStephen]

I believe the cone-bottom tanks in API-12F would normally have support beams underneath the bottom to transfer the load directly to the foundation- not a suspended bottom as assumed by API-620. Anyway, API-12F fabricators should be able to clarify how they normally do this.