Allowable Buckling Limit for External Floating Roof Tank 1

[MOHAMMED89]

Dear All,

What is the acceptable buckling range for the External Floating Roof(EFR)Deck Plates.

In my Double Deck EFR, The buckling is occurred due to the weld imperfection, I would like to know the acceptable criteria/limit for the buckling. The buckling is happened in the bottom side of EFR bottom plate. I have checked in API 650 and ASTM A6 but none of these code provide the guidance for EFR.

Thanks in advance.

 

[Dhurjati Sen]

If there is no criteria then it would mean that the code writers did not anticipate nor do they tolerate buckling of the floating roof plates.

DHURJATI SEN

 

[MOHAMMED89]

Dear Dhurjatu Sen,

Thanks for your response, Actually the client is asking for the code reference for the allowable buckling limit for EFR. so please share any other related marine/ offshore standard/code or any company specification for the same.

 

[LittleInch]

Other than general "workmanship", there isn't one.

Is there anything written into your particular specification or order?

Or did someone just buy an "API 650 tank"??

Bottom plate doesn't matter so long as there isn't a hole in it. It's the pontoons which matter.




Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[HTURKAK]

,

IMO, there is an implicit requirement at API 650.

Copy and paste of the relevant section;


Provide more info . to get better responds.. what is the slope of bottom deck ?... provide the service, tank dimensions, some descriptive pictures..

 

[IFRs]

If there is no criteria in API 650 or 653 for this, it must be because it really does not matter and/or for as long as anyone can remember generally acceptable workmanship has been the industry experience and it was not necessary to add it to the standards. I'm sure somewhere along the way some contractor was so terrible they got kicked out but just bcause they were terrible and did not care or have the skills to do a decent job. If you are seeing a condition you don't like, you'll have to make your own criteria and somehow get it into the contract. If you have a meter of buckle in 10 meters of deck there might be a problem. If the deformation will cause structural instability or performance issues you have a good case for remediation. Does the designer of the floating roof have a problem with the poor quality of the work? Is the work poor quality or is it unavoidable for the lapped and welded sheet? If you have sagging bottom plate that is not welded to the double deck structure it might be perfectly serviceable when floating. Then again, it might not. For us to help we'll need data.

 

[saplanti]

I totally agree with IFRs. Could not be said better.

 

[MOHAMMED89]

Thanks all,

Actually the tank dia is 72m with double deck CS EFR, Bottom plate of EFR is flat with out any slop and top plate have slop of 1:64 towards the drain sump, The tank is designed to handle crude oil.

I got answer to my question from above threads, Thanks all.

 

[LittleInch]

mohammed, "I got answer to my question from above threads, Thanks all." That's great, but can you tell us what you're going to do??

This thread need a proper ending not left hanging in mid air like your floating roof....

Please

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[MOHAMMED89]

Dear LittleInch,

Sorry for the incomplete reply.

Actually from above responses from experts it is understood that no code (API 650/API 653) provide us the guidance for the buckling limit, and i checked with our site QAQC team as well to understand the buckling rate and root cause for the buckling. from there i came to know that the buckling is due to the improper weld sequence followed by the contractor and also due to the improper heat input (lack of skilled workmanship).

And how i conclude is that i have checked in ASTM A6 for the flatness limit (in API 650, this is referred for the shell course buckling)and also checked the structural design code IBC 2009 (Floating roof is considered as the structural item, as still it is resting on the leg. So by comparing these two values, the buckling limit as per IBC is more more stringent and same is construed as applicable of EFR.

Thank You