huangyhg

api 620 vs. api 650.
hi,
i'm checking the shop drawings for a low-pressure gas steel storage tank. the contractor submitted the design based on api 650. i think the design need to comply w/ api 620 instead. however, i'm not familiar w/ either code.
1- are there major differences that you can think of that can alter the design of the tank, i.e., min welding, min gage, certain astm, special inspection, allowable stresses, corrosion protection, special loading, etc.
2- what resources are out there that can shed light on the application of either codes, i.e. text books, solved examples, seminars, etc.
let me know if you need further info.
cheers!
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api-650 is used primarily for liquid storage tanks. it is applicable to flat-bottom tanks with a cylindrical shell. appendix f of the standard includes provisions for design pressures up to 2.5 psi. it refers to api-620 for roof designs of certain tanks.
api-620 is used for tanks storing vapor or liquid up to 15 psi, and is applicable to any tanks having an axis of symmetry. it includes flat-bottom tanks but is not limited to them.
generally, api-620 is more conservative, with lower stresses, etc. corrosion protection is specified by the owner, and is not specifically required in either standard. the seismic design of api-650 is more up-to-date, and some of the appendices of api-650 are useful for api-620 tanks. api-620 tanks are not that common.
if the tank in question doesn't actually fall under either code (floating gasholder, for example), there would not be a compelling reason to use one over the other.
api does have seminars from time to time, and there are some books available on tank design and tank regulations- check on amazon.
mo74se,
just out of curiosity, what are you checking for if you are not familiar with either standard?
joe tank
jstephen: thanks a lot! i checked amazon before and there are lots and lots and lots of books out there all claiming to be the "one". i just wanted to see if anyone who's more familiar w/ these kind of tanks would recommend a really useful book. anyway, thanks again!
joetank: the tank is a spec item. the check is for overall conformance nothing else. the analysis, design and detailing are done by a pe who specializes in those tanks. i thought it's a good opportunity for me to get my feet wet and learn something new.
cheers!

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