MAWV for API 650 Tank

[SJEC]

I have a job to put nitrogen blank into an api650 tanks.
Before that, I need verfy the MAWV for this tanks.
The tank have column-supported cone roof and covered by V7.1.
Has nothing on Truss-supported Cone Roof Tanks ? How do we proceed with designing the roof for Vacuum in such cases ?

 

[JoeTank]

You will need the services of a engineer experienced in storage tank design procedures to sort this one out. Truss supported roofs are not frequently used so this is not addressed in API-650.

Joe Tank

 

[MJCronin]

SJEC

Request a detailed third-party design review by an experienced "storage tank" engineer. (I am assuming that this vacuum rating is not incorporated into any design drawings that you have in your records)

Do not be surprised and disappointed if your existing tank cannot sustain MAWV as little as - 3IWC.

The design vacuum is an issue that cannot be successfully applied to existing tanks ..... it must be incorporated into the design before that tank is built.

This is my opinion only

-MJC

 

[SJEC]

The tank is pretty old ( it was built 196X).

Our process guy want apply 1" wC on it. Per the latest API650 appendix V, Vacuum lower than 1" WC do not need any additional calculation.

My question is that my old tank can exempt calculation due to this item?

Thanks for your advice MJCronin.

 

[MJCronin]

SJEC

Have your process guy on top of the tank when the 1" vacuum is applied

Its only fair......

-MJC

 

[LeonEarle]

SJEC,

Even back in the 1960's API's position was that tanks built to the minimum requirements of the standard could withstand 1" water vacuum without anything additional. If you can find API on the nameplate, a nameplate drawing, or find the certification letter certifying that the tank was built to API 650, you're home free. I would have to look at my superceded issues of API 650 to confirm, but I don't believe hat API addressed truss assembly supports back at the time this tank was built. That may be your hang-up.

Best of Luck

 

[SJEC]

Thanks for all above advices.

I found that +/- 1.5 WC design pressure was shown on original drawings.