Roof Live Load

[curlyjackme]

Per API 650 5.2.1f the Minimum Roof Live Load on the horizontal projected area of the roof is to be 20lb/ft^2, or may be determined by ASCE 7 , but shall not be less than 15lb/ft^2.

My question is can this load be reduced to 0 lb/ft^2 at the owner's request and the tank still be considered an API 650 tank?

In section 1.1.1 it states that this standard established minimum requirements for material, design, etc...

 

[bimr]

The Code states "shall not be less". The important word there is shall.

No, because the tank would not meet the minimum requirements.

 

[IFRs]

bimr is correct but why would you want to reduce the live load to zero?

 

[JStephen]

Ditto to the "Why?" comment.

Note that you can build an open top tank if desired.

Once you have enough structure to support the weight of the roof itself, there's not that much difference in supporting the live load or snow load.

 

[Syahar1975]

Agree with BIMR.

Like IFRS and JStephen said "there must be a reason why the client request to reduce to 0"

In this case open top tank is the best option. But need also to consider the product to be stored.

 

[curlyjackme]

Thanks for the comments. The only reason for the eliminating the live load was to reduce cost. But I don't believe that cost should be used to compromise the integrity of the design for a tank. And due to emissions these tanks cannot have a open top. Again thanks.

 

[IFRs]

There are minimum loads for a reason, not the least of which is to have a structure you can walk on if needed. Also, if emissions are a concern, then suspending an aluminum internal floating roof may be in your future.

 

[curlyjackme]

IFRs you are correct it will be designed with an IFR but it is going to be steel and not aluminum. Again thanks for all the reply's.

 

[fegenbush]

How do you weld the top side of the roof plates if the roof is not designed to support a live load?

 

[curlyjackme]

fegenbush, sorry for the delay in answering this, but this was also one of my concerns. The answer I got was the beams and plates have a factor of safety built into the allowable stresses for design. I do not agree with this, I believe the minimum live loads must be applied in the design of the tank to account for any unseen loads that the tank may see.