It has been my experience that:

1)Fuel Oil Tank Cleaning - depends on the frequency of water drainage and the quality of the fuel purchased. Perhaps once every 3-5 years
  
2)Inspection - Exterior "walk around" inspection - yearly. Detailed interior inspection: first one - three years after commisioning, then every five years

3)Repairs (Change of the 10% of the bottom, minor repair in shell and roof) - Depends on what is found during inspection

4)Hydrostatic Test - only one test should be done during commisioning

My opinion only

   

MJCronin, Thank you very much for your answer. But i think i dont explain well what i need. I need to know how much time takes and what technology use to every point, not the frequency.

regards
 

How big is your tank?
How clean is your fuel?
How efficient is your cleaning crew?
Do you have a multi-section 40-ft ladder that will fit through your manway, or will scaffolding need to be erected?

An Internal Inspx, without vacuum boxing the floor or MFL scanning, takes me about 3 hours.  After the tank floor is mostly clean to bare metal, and ALL weld seams are down to bare metal.  And the shell is clean and the first and last 10-ft [upper & lower shell] are bare metal, and there is a means to get up to the upper 10-ft of the internal shell and perimeter of the roof.

With a 'clean' nonwaxing fuel, this *can* be all done in 24-36 hours.  But I have not seen it done this fast yet.  With a LOT [3-ft / 1 m] of gummy residue, it can take well over a week.

The OP says what technology is needed? so he must be prepared to buy whatever is needed to do the job.   

Thank Duwe6, its a fuel oil tank 55.000 bbls, 100'diameter  X 40' height, and im looking to improve all the process using the best practices.
For example, for the cleaning im thinking in chemical cleaning, MFL and ACFM for inspections. I want the fourum opinion for every step:

1)Cleaning  
2)Inspection
3)Repairs (Change of the 10% of the bottom, minor repair in shell and roof)
4)Hydrostatic Test

cloa, your are right.

Please, any one can help me?