api 650

huangyhg

api 650
i am working on requesting quotes for shop fabricated steel tanks that will be used to hold various petrolium products. the tanks are 20000gal and smaller, and are leg supported. i sent the request out and got responses, but while in the bid process i had conversations with some vendors (not all) that lead me to undersatnd api 650 is not applicable to leg supported tanks. yet those vendors still gave me a cost to do the work ...?
i read the api code (i just ordered them) and i agree it does not seem to accomodate leg supported tanks.
does anyone no what code covers leg supported petrolium holding steel tanks?
what is standard for my request? i know for a fact we have requested api certification for leg supported tanks and got it from vendors. how are they doing that? i think i am missing a very important part of the puzzel and am not able to find a reasonable and consitent answer from anyone i talk to.
thanks in advance.
try api 620.  i believe it covers other tanks as well as the fully supported, flat bottom tank.
well throw those quotes away and strike them from the list.
biginch...you seem confident that api 650 does not cover leg supported tanks. is that correct? how do you think we have been able to get certification, complete with the certification plate? is it possible to inspect a leg supported tank and see if it meets the requirements of api 650, except for the legs i suppose, and then write a document that certifies such? seems odd, but i have seen the certs. can you build a tank to api 650 requirements, except for the legs? or is there another code that specifically covers leg tanks?
sorry for the asking the same question 10 different ways.
thanks
have you really read api 650?  look at the details they give and it's quite clear that it cannot apply to anything but ground supported tanks or tanks on an elevated, thick, stiff concrete mat.  the fact that the foundation loads will be concentrated and not distributed will make a difference on the stresses in the tank walls and bottom unless special provisions are made.
hey, no offense meant, but since you mention it, its not exactly like api comes around and looks at each tank and hammers the cert on the nameplate themselves, but actually i was referring more to the use of outdated specs by,
1.) by the original poster
2.) by the mfgr for not taking what i would consider clear and appropriate exceptions.  or, rereading, maybe faint whisperings of exceptions has something to do with the asking of the original question.
plz see follwoing,
when you as a purchaser specify a leg-supported tank designed and built to api-650, you are going to get a tank designed and built to api-650 "to the extent applicable".
there are a lot of tanks built that do not fully fall under the various tank standards.  for example, api-650 is titled "welded steel tanks for oil storage", but you'll find it used for water, wastewater, ethanol, molten sulfur, acids, food products, agricultural products, all manner of chemicals, etc.
in the case of leg tanks, awwa d100 does include that configuration for municipal water towers.  however, it really isn't any assistance in the design of the tanks, and there isn't any great advantage in specifying it for oil tanks (it's intended for water storage, of course).  similarly, api-620 could perhaps be applied to these tanks, but doesn't really include useful design information  pertinent to the tanks, and is intended primarily for a different application (ie, pressurized tanks).
unlike pressure vessels, there is not a requirement that all tanks be built to this or that code.  different industries have developed standards for the more common applications.  those standards are routinely applied to less common applications simply for lack of anything better.  it may seem odd to apply api-650 to these tanks, but if the alternative is no standard at all, it makes more sense.
if you'll refer to fig. 8-2 in the current api-650, the certification states that the tank "meets all applicable requirements of api standard 650", and that statement could be made about tanks that deviated considerably from the type of tank api-650 is intended for.
having been on the vendor's side of the fence before i've got a few guesses as to what is happening.
1) you're dealing with a salesman who doesn't know api 650 from his . . . well, you know.  he's just noddin' his head to make the sale.
2) the vendor perfectly knows api 650 is not really applicable but he'll comply with the parts that are relevant and exercise good engineering judgement otherwise. he doesn't want to embarass you (or trouble himself maybe) by explaining that you've spec'd the wrong code.
3) the vendor is a complete moron and he doesn't realize the cook book formalus in api-650 won't apply to leg supported tanks and he's gonna apply them anyway. buyer beware!
the bottom line is you really need to feel comfortable that the vendor knows what he is doing. you can help by not specifying codes that, imho, really aren't applicable.