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API 650 Foundation Tolerances

API 650 Foundation Tolerances

API 650 Foundation Tolerances

I am designing a cylindrical water tank with a concrete ring beam.  I am attempting to conform to the standards of API and would like to incorporate the subgrade preparation requirements in my specifications.  I have portions of the API 650 that reference Section 5.5.6, which I do not have. This section is referenced in Appendix B under B.4.2 "Earth Foundations with a Ringwall".  It specifically states, "Tank foundations must be true to the specified plane within the tolerances specified in 5.5.6".  What are these tolerances?

RE: API 650 Foundation Tolerances

HI pcronin (Structural)

Tank References

Aboveground Storage Tanks
by: Philip E. Myers
ISBN: 007044272X

  A comprehensive text discussing all aspects of aboveground storage tanks. Topics include codes & standards, materials, corrosion, foundations, seismic concerns, roofs, fire protection, emissions, inspections, and settlement. An excellent reference for those unfamiliar with certain aspects of tanks.


RE: API 650 Foundation Tolerances

While it would be best for you to aquire the actual document in order to see the entire section, it says: "Where a concrete ringwall is provided under the shell, the top of the ringwall shall be level within +-3mm (1/8 in.) in any 9m (30ft) circumference and +-6mm (1/4in) in the total circumference measured from the average elevation."

Also - why not use AWWA specifications?

RE: API 650 Foundation Tolerances

Thank you for the quick replies.  I am using the AWWA for the design of the tank, but I am checking it against the specific requirements set forth by the API.  I appreciate your help regarding the tolerances of the concrete ringwall.  That information is consistent between the API and AWWA.  I was wondering if the API standard has any specific requirements regarding the acceptable tolerances of the final grading within the tank structure to maintain the recommended minimum 1" in 10' slope of the interior grade.  Based on your prior responses, I am assuming that it does not.  Thanks again for all of the help and the rapid responses.

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