Storage Tank Shell Course Replacement 3

[Indunilpra]

A 22m diameter and 15 m high (Shell height) Self supported Domed roof above ground tank requires shell plate replacement in 2nd, 3rd, 4th and 5th shell courses out of 8 shell courses (See Attached Image). It would be very much appreciated if a tank repair expert could suggest a repair methodology.

 

[LittleInch]

Why are even thinking about trying to replace 50% of the tank shell?

Just demolish it and start again.

Or cut between 6th and 5th course and lift it off the start again from course 2 upwards.

But I just can't see it being economic to repair.



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

 

[JStephen]

If space is available and if a large crane is available, remove the roof and upper shell, replace shell as needed, and set roof and upper shell back on.
It may or may not be economical to do that, check pricing both ways.

 

[IFRs]

What's the big deal? Cut out shell plate in "windows", replace, repeat. If you want to replace an entire ring, weld I-beams vertically on 10 foot spacing, remove the ring, install a new one.

 

[MJCronin]

LittleInch's first response wascorrect .... Nothing lasts forever....

Patches on patches on patches is soooooo Third World

Time for complete tank replacement

MJCronin
Sr. Process Engineer

 

[IFRs]

Capital budgets and maintenance budgets are very different, sometimes owners do what seems odd or illogical to us but it meets their budget goals and limitations.

In my world, replacing sheets is not that unusual, I'm replacing rings 5, 6 and 7 of a 7 ring tank now. It's easy really - cut out a 20 or 30 foot section creating a window in the shell ring, lock in a new sheet in place, weld one vert and then the bottom round seam, cut out the next section, lock in a new sheet in place, weld one vert and the round seam, proceed around the tank.

Ultimately you are left with the top portion of the tank resting on and held in place on the lower portion with fit-up gear, or stitch welds, C-clips, vertical stantions, etc. It might sound unstable but really, it's not - or at least that has been our experience - and we are very careful to monitor weather conditions, etc.

A tank mostly could not care less if a window is cut out and if you place the new sheet quickly there is little risk of a storm deforming the tank though there is some risk of the weight above deforming the tank at the open corner depending on the tank size, shel lthickness, etc.

Depending on the extent and duration of the repair, the likelhood of seismic or wind events, we might weld say W12 x 45 posts floor to top angle to maintain roundness, stability, etc.

I'm also fortunate to be working with very very experienced tankies...

 

[JStephen]

One other thing I'll mention- when replacing the shell, there's no particular reason to cut out whole plates or to match existing plate lengths- so think in terms of length to cut out, not individual plates.

 

[LittleInch]

IFRs.

Your experience is far more than mine.

I think the key is in your last sentence.

This sort of repair is not for the inexperienced or a leap into the unknown and for the OP to apparently be requesting a repair methodology is quite alarming....

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

 

[Dhurjati Sen]

Partial shell repair as per API 653 could be carried out but asking for repair methodology / procedure for free is too much, even for the Third World.

DHURJATI SEN

 

[IFRs]

Dhurjati Sen - why the "third world" comment? I don't see how that contributes to a technical discussion between engineers or is helpful or kind or appropriate. If you meant it as a joke, same respose...

 

[LittleInch]

OP comes up as LK - Sri Lanka.

But I agree - too many insults flying around. The point still stands regardless - it seems a bit worrying that someone is asking for a methodology for something like this.

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

 

[Dhurjati Sen]

Dear IFR,

Refer MJ Cronin"s post above.

Warm regards.

DHURJATI SEN
Kolkata, India

 

[Indunilpra]

Thank you very much for the valuable comments made by everyone.

This is my first tank repair work in this scale.
I have referred lot of technical literature, expert ideas, case studies and prepared a reliable methodology while minimizing the risks involved.
Interestingly, it is very much similar to the method suggested by IFRs which has built confidence in my repair methodology.
I firmly believe that no one is able to become an expert in any discipline at once. It requires experience, knowledge, experts advices etc.