API 12F maximum capacity? 3

[SteveMousseau]

Hi Eng Tips forums,
I have tried searching both these forums and the internet at large for the answer to what seems to be an easy question...

Are API 12F tanks limited to the standard sizes in Table 1? I.E., is the max capacity for a 12F tank 750 BBL? My thinking is that then any larger shop fab tank would be API 650 App J?

The reason I ask is our project is procuring 1000 and 2000 BBL tanks and I am trying to firm up the testing requirements. Vendor stated tanks to be API 12F modified. API 12F required 1.5 x design air test. but vendor is saying 1.1 x design for air test. But now i'm wondering if it should be API 650 requirements.

Your help is much appreciated,

Steve

 

[JStephen]

API-12F is indeed limited to the sizes tabulated.
One option is to use API-12D, which can be completely shop-fabricated if conditions permit.
One option is to use API-650 Appendix J. This changes some of the detailing and pressure requirements considerably.
Generally, for oilfield-type applications, it'd be API-12F/D, for other applications, API-650.
UL-142 would be another possibility- typically used for gas-station type tanks.

 

[fegenbush]

If your tank is to experience any pressure, do not use 12F.
If your tank is subject to any wind over 90mph (ASCE 7-05), do not use 12F.
If your tank is subject to seismic loading, do not use 12F.
If your site is in any place other than a remote location, do not use 12F.

The requirements for API 650 Annex J are more stringent, but I think that you will be happier with the outcome versus a 12F tank.

 

[SteveMousseau]

Thanks JStephen and fegenbush!
This is for a gas plant (remote location; condensate and produced water tanks. Design pressure is 16oz/in^2, wind design is 84mph. The design is API 12F modified, which I assume is because the tanks are larger than 12F specifies. I work in Quality so I'm just confirming the appropriate tests are done. I.e. 1.5 x design as per API 12F or hydro as per API 650. From talking with a few collegues with more experience in the matter, I was told we typically do the API 12F test.

Thanks again!

 

[IFRs]

The pressure is 1 psi or 144 pounds per square foot, pretty high compared to the tank weight, check for anchors being needed especially in combination with the wind overturning moment, you may want to check the top compression ring being strong enough especially if your tank is larger. I have not heard of 12F Modified, it is either 12F or not.

 

[fegenbush]

IFRs,

We discussed 12F Modified tanks on November 11th in New Orleans. The conclusion that was agreed upon was the same as yours. There is no such tank as a 12F Modified according to API. That being said, a 12F Modified tank is when the fabricator adds an additional 8 ft shell ring to a 750 bbl size to create a 1,000 bbl tank.

SteveMousseau,

As IFRs mentioned, 1 psi is considerable pressure for a tank this size. Anchorage will be required for pressure. Additionally, the standard size on which the 1,000 bbl tank is based (750 bbl) is only rated for half of what you are prescribing as the working pressure. As advised previously, I strongly recommend an API 650 Annex J design for safety, product containment, and venting.

 

[SteveMousseau]

So now I'm studying up on Annex J from everyone's recommendations. For testing, J.4.2.2 allows for air test in place of hydro: "c) An internal air pressure of 14 kPa to 21 kPa (2 lbf/in.2 to 3 lbf/in.2) gauge shall be applied to the tank. For tanks with a diameter of 3.7 m (12 ft) or less, a maximum pressure of 35 kPa (5 lbf/in.2) gauge shall be used."

This seems like a lot of pressure for a tank air test.

 

[JStephen]

One thing to note is that the pressure test of Appendix F is done after the tank is attached to the anchor bolts, so it can't all be done in the shop.

 

[Duwe6]

"This seems like a lot of pressure for a tank air test. "

It is. Stand back at least 50-ft while at max pressure. Then drop the pressure at least 10%, THEN approach and apply the soap solution. It's pretty rare these days, but some [badly welded ones] go KABOOM.