Calculating stresses in API 650 tank filled past shell/roof junction
Calculating stresses in API 650 tank filled past shell/roof junction
(OP)
I have been asked to analyze the stresses caused by filling an API 650 storage tank above the roof to shell joint.
The tank(s) are mounted on concrete ring wall foundations but are NOT anchored to the foundation by use of anchor chairs & bolts.
Where would the max. stresses occur in this case, at the floor to shell joint or at the roof to shell joint? How would they be calculated, and what would be any indications of overstress other than a complete failure?
As far as I can tell, the code does not address this issue.
Yes, I know that you're not supposed to overfill a storage tank, but our operations people have done it in the past and there is no easy solution to address this problem instrumentation-wise.
Any help or suggestions would be greatly appreciated.
The tank(s) are mounted on concrete ring wall foundations but are NOT anchored to the foundation by use of anchor chairs & bolts.
Where would the max. stresses occur in this case, at the floor to shell joint or at the roof to shell joint? How would they be calculated, and what would be any indications of overstress other than a complete failure?
As far as I can tell, the code does not address this issue.
Yes, I know that you're not supposed to overfill a storage tank, but our operations people have done it in the past and there is no easy solution to address this problem instrumentation-wise.
Any help or suggestions would be greatly appreciated.





RE: Calculating stresses in API 650 tank filled past shell/roof junction
The bottom course required thickness can be confirmed using section 3.6.3 or 3.6.4 of the Code with H set equal to the overflow level.
The Roof-to-Shell junction can be checked against Appendix F requirements with regard to an internal pressure equivalent to the liquid head above the junction (to overflow level).
Only if either check revealed that Code boundaries were exceeded would you need to lie awake at night worrying, and to consider doing a more detailed analysis.
Regards,
John
RE: Calculating stresses in API 650 tank filled past shell/roof junction
Roof seam could fail
Top angle could fail
Roof to shell weld could fail
Upper shell could could buckle
Shell to bottom weld could fail
Bottom seam could fail
Steve Braune
Tank Industry Consultants
www.tankindustry.com
RE: Calculating stresses in API 650 tank filled past shell/roof junction
Sorry, I can't help with the stress calcs.
I may be able to help with the instrumentation part.
Why can't instrumentation help prevent an overfill?
RE: Calculating stresses in API 650 tank filled past shell/roof junction
Steve Braune
Tank Industry Consultants
www.tankindustry.com
RE: Calculating stresses in API 650 tank filled past shell/roof junction
Some research along this line has been done in connection with frangible roof studies. Both API and WRC have books dealing with that topic.