Secondary Stiffening-Cone Tank API 650, 1961

[LurmClaxton]

We have a number of cone tanks at our facility which I believe were built to an early 60's API650. They do not have any external stiffening rings.

They have not suffered from internal shell corrosion and the shells are effectively at nominal thickness. My interpretation of 60's API 650 is that cone tanks not built to App D don't require secondary stiffening.

Would people agree that non ADB cone tanks don't need secondary stiffening (to code).

Also does anyone know how I can get hold of a API 650 first edition. I can't find any for sale

Thanks in Advance

Lurm

 

[JStephen]

External stiffening rings are not an inherent requirement. Per the current standard (and for quite a few years past), you checked the shell for the need of external stiffeners based on as-built shell thickness. In a lot of cases, tanks simply don't require any external stiffening. In a lot of cases, it is more economical to increase the shell thickness rather than add the stiffeners. Due to differences in time and material rates, that determination will vary from time to time, from contractor to contractor, from place to place.
If the tanks are in place, I can't think why you'd go back and start trying to re-evaluate a design feature per the original standard.