How many repairs before replacement for storage tank? 5

[hamidinho]

Hello everyone,

I have a quick question, how many repairs can we make to a bottom of a storage tank before it is required for us to replace it all ? If it is mentioned in API 653 which section will i found it ?

Thank you

 

[LittleInch]

Make enough repairs and you'll end up replacing it....

Don't believe this is in the realms of the code to determine what is really an economic decision.

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

 

[hamidinho]

I'm a junior engineer in this filed that don't have much experience so i thought that it would be mentioned in the code. Thank you for your answer so it depends on its state.

 

[LittleInch]

I think so, but others may have a bit more information.

But these things are usually an economic or schedule issue in that repairs are normally more expensive per m2 than a complete renewal.

The tank floor is just there to stop the contents coming out, it's not really a structural thing.

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

 

[MJCronin]

This is strictly a personal opinion ... but here goes ...

I believe that it is worthwhile to periodically excercise vendors and contractors to get up-to-date estimates for equipment replacement.

Anytime a repair estimate exceeds 40% of the estimate fo an entirely new component, the components should be replaced.

Pumps, compressors etc are pretty easy to get replacement costs ..... but

Periodic accurate replacement costs for large custom built tanks, pressure vessels, columns etc ... may be more difficult

MJCronin
Sr. Process Engineer

 

[hamidinho]

Thank you and your replies are very appreciated. So it's more an economic issue than technical.

 

[IFRs]

You have a very valuable piece of capital equiment. Try not to treat it like an afterthought. How long would you patch the tires on your Mercedes? What risk are you and your company willing to take? Your first responsibility as a professional enginer should for the public safety. Failure can be an environmental disaster that might affect your grandchildren and beyond. Failure can be subtle (a small leak) and become very expensive to fix and remediate. Imagine yourself and your boss in front of a judge trying to explain why your ocmpany chose not to replace the bottom after multiple repairs. "The API standard did not say we had to" may not going get you very far, or explain it to the neighbors who were affected...

 

[hamidinho]

Such a good point you made here. Thank you i'm learning many here day by day

 

[Dhurjati Sen]

Above every thing else, it depends on the operation down time.
If you have spare tanks and can afford leaks hence wastage of product, no issues regarding pollution of the environment, you may use the tank forever.

What is normally done then?

Carry out MFL of the bottom plates, make an assessment, check the next shutdown opportunity and take the decision for repair or partial/ total replacement.

DHURJATI SEN
Kolkata, India

 

[FacEngrPE]

When contemplating replacing a tank bottom, inspect the shell also. Failing to understand the condition of the entire tank may result in real trouble.
Allied Terminals Fertilizer Tank Collapse
November 12, 2008 a two-million-gallon liquid fertilizer storage tank collapsed at the Allied Terminal distribution facility in Chesapeake, VA.
Tank was originally designed and constructed in 1929 for petroleum product storage.
Report attached (it is useful to know what has happened so we can avoid repeating prior failures).

 

[blacksmith37]

May be obsolete but Amoco covered many old bottoms with fiberglas / polyesther. Some FRP bottoms had to be 30 years old when I retired but I did not hear of problems ( I should have because I wrote up some of the procedures). Often these tanks were in locations where ground water was monitored for contamination.

 

[IFRs]

blacksmith37 - nice to know it is possible to retire from the industry, it's been 46 years and I'm still too stupid to go...

 

[r6155]

Acoustic Emission Examination, during operation, give you god information about leaks in the bottom.

Regards

 

[r6155]

Acoustic Emission Examination, during operation, give you GOOD information about leaks in the bottom.