API 650 two-inch chime requirement
API 650 two-inch chime requirement
(OP)
Why does API 650 require a two-inch chime? Is there a structural basis?
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API 650 two-inch chime requirement
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RE: API 650 two-inch chime requirement
RE: API 650 two-inch chime requirement
RE: API 650 two-inch chime requirement
If it was for vacuum loading, then larger tanks would require a larger chime, which is not the case. Appendix A or J may allow a smaller chime.
I don't think API-650 addresses the situation with clearance between anchor bolts and the chime.
RE: API 650 two-inch chime requirement
RE: API 650 two-inch chime requirement
Appendix (Annex) J tanks do have a smaller chime requirement. See J.3.2.3 and note that the bottom may be flat flanged (no chime) or a minimum of 1" beyond the toe of the shell-to-bottom weld. Appendix (Annex) A tanks can be quite large. For instance, it is possible to construct a 100 ft diameter x 32 ft high tank to Appendix (Annex) A so I do not see how the chime requirement should be relaxed for that portion of the standard.
RE: API 650 two-inch chime requirement
If I remember right, there is an issue in the shell analysis theory as to whether the bottom plate is assumed to have a plastic moment both inside and outside, or inside only, and perhaps the additional length was to help justify the assumptions there. If that's the case, then notching around a bolt should have minimal effect on it.
RE: API 650 two-inch chime requirement
When I add these up in my mind I get an inch or more; i presume that is how the 2-inch requirement arrived. When a tank is built in the field using 'classical' methods, the floor sketch plates are cut from straight plates. At that point, any reasonable floor extension - chine - can be established 1", 1.5", 2", 2.5" etc. For a new tank, I personally am perfectly happy with a nominal 2-inch chine, that never goes below 1.5" from the outer face of the shell.
RE: API 650 two-inch chime requirement
RE: API 650 two-inch chime requirement
RE: API 650 two-inch chime requirement
Chime is a term to describe the required projection of the bottom plates beyond the shell as described in 5.4.2 of API 650.
RE: API 650 two-inch chime requirement
"the edge or rim of a cask or drum"
"the projecting rim at the end of a cask"
Specifically, the bit of bottom plate that extends outside the shell on a tank.