Closing nozzle opening on the shell of a new API 650 Tank 1

[Ramil Abbaszade]

Dear tank specialists,
We have 39.9 m I.D Gasoline Storage Tank designed as per API 650 currently being under construction. Two 4" nozzles are attached to first shell course plate which is 18mm thick. During the construction, it has been known that elevation of these nozzles are wrong and will cause some operational issues. It was initially suggested to keep these nozzles blinded as spares. But now client wants to eliminate them.
As this is a new tank being still under construction, I checked api 650 itself for repair and it only says for large deffects on the tank shell either "butt welded shell plate replacement" or "lap welded patch plate" to be considered. Since shell plate will not be replaced at this stage of construction, client is asking why butt welded patch plate is not applied instead of lap welded patch plate?

What is the best way of closing these openings? Is butt welded or lap welded patch plate suitable to solve this particular issue?

 

[MJCronin]

IMHO ...... The client should accept them as spares ...

as years pass, the maintenance department will appreciate it

MJCronin
Sr. Process Engineer

 

[JStephen]

If they were completed and meet API requirements, I'd say, leave them in, even if it is known for sure they will never be used. Simply because there's no advantage to removing them.
That said, I would assume to plug up the hole with butt-welded plate on a new tank. Watch weld sequence etc. to avoid cracking in that configuration.

 

[IFRs]

I'd cut them out and replace then with a butt welded insert plate(s) of the same material as the shell plate, cut out around them to eliminate any heat affected zones, stick with all weld spacing requirements. I don't think anything in API 650 prohibits this. Do NOT use a lap welded plate, do NOT consider this a repair. Don't give the unused nozzles a chance to leak, be openned when they should not be, etc. There should be spare nozzles elsewhere. If they are at the wrong elevation you'll need new ones at the correct elevation that can be installed in the inert plate or a thickened insert plate. You could also put a manway there!!1

 

[Ramil Abbaszade]

Good day,

New nozzles will be installed at the required elevations, it is not problem.

I just checked out the subjected nozzles. There are 4 numbers of 2" Nozzles and 2 numbers of 4" nozzles welded and completed on the tank shell being useless. I would also prefer to keep them spare and blinded. But client see this as a last option.

I wonder if these nozzles are decided to be eliminated from tan shell, what would be the disadvantage of using lap-welded patch plate to close the nozzle openings? Or Is there any advantage of full penetration patch plate to close these openings? (since opening diameter is also small on 2 inch nozzles, distance between welds can be less being heat affected). Should it also require the grinding of weld seams and reducing the thickness of plates and etc?



Best Regards,
Ramil

 

[IFRs]

This is a new tank, a major capital investment that will last a long time. Do it right and forget about it. Cut them all out and install an insert plate. Lap welded patches are not part of API 650 and lap patches are not as strong as butt welded inserts. API 653 lap patches are not allowed over 1/2" thick. If the client does not want to pay for a proper API 650 tank, that's OK - it's their risk, but I'd offer them the best long term, strongest, standard compliant fix first, and if they insist on something outside API 650 make it clear that it is their risk (even if you evaluate the risk as low, it is still not yours to take). I have little sympathy for a $2 fix on a $2,000,000 tank.

 

[LittleInch]

Are they spread out around the tank or in one location where as IFRS say, you could cut out two or three in one go and weld in a larger plate.

Or if you want to re use them why not cut out a larger square or circular section and then weld that where you actually want the nozzle. only need to be cut beyond the HAZ, then replace the old hole with a new plate?

Drawings or photos always helps and sometimes we can see things which make the solution less effective.

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

 

[Ramil Abbaszade]

only 4 nozzles - 2" and 4" nozzles at two location 180 deg apart, are close to each other (same elevation but 2 deg orientation difference). Other two number 2 inch nozzles are at different orientations far from the others.

 

[MJCronin]

Ramil....

I believe that the lesson that you can learn from this discussion is that there are legitimate differences of opinion on this issue..

I cannot understand how a contractor can deliver a "NEW" API-650 tank to a client with large lap-type repairs and call it "code compliant"

I cannot understand how competently designed and fabricated spare nozzles with blinds poses any type of leakage risk ... how on earth can a lapped plate repair, (designed, fabricated and installed to mysterious standards) can be superior ?

IFRs offers good advice when he suggests butt-welded insert plates ....

Wisely, LittleInch suggests a Code and Contract compliant repair with a new butt welded plate, not the common "iraqi special lap plate"

My opinion only ...

MJCronin
Sr. Process Engineer

 

[Ramil Abbaszade]

Gents,

Thanks for sharing your opinions. It is appreciated!

The problem is already solved at site by welding butt-welded patch plates in. I have attached some photos for you.

 

[Ramil Abbaszade]

2nd photo

 

[Ramil Abbaszade]

3rd photo.