How can repair leaking at vent hole of reinforcement pad on roof Tank during tk operating phase 1

[sangnguyen038]

Hi Sirs,
Regarding to repair tank work during operating.
Could you advise, We are founding leaking point at vent hole of reinforcement pad of roof. How can repair leaking at vent hole of reinforcement pad on roof Tank- API650 during tank operating. We can be proposed the Vent hole on reinforcement pad to seal by welding or not? Or where mention we can repair this defects.

Regards,

 

[IFRs]

On the fixed roof?

 

[sangnguyen038]

Yes,Mr. IFRS. this the fixed roof of tank.

 

[IFRs]

Is this a floating roof tank?
Is the tank designed for any internal pressure?
If the product stored is flammable, and it needs to be fixed, fix it without hot work.

 

[sangnguyen038]

Is this a floating roof tank? ==> This fixed roof tank, without floating root.
Is the tank designed for any internal pressure?==> No. This storage tanks, this have operation pressure -4/+45 mbar.
If the product stored is flammable, and it needs to be fixed, fix it without hot work.
=> When repair the product shall be discharge and good condition for hotwork.
So: I want to your advice how can repair it, we can seal weld or use plug for this vent hole on reinforment pad or not. Can code Api 653 mention repair or not.

Thanks Mr. IFRs

 

[LittleInch]

How do you know its leaking if its on the roof? See or feel vapour coming out?

Selling the vent hole is at best a temporary fix and welding sounds like a bad move. Some sort of plug would be better.

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

 

[sangnguyen038]

Hi LittleInch,
We see the vapour come out on this venthole. We have planed remove welding joint nozzle to roof==> Make bevel ==> Re-welding then the Air test for reinforment pad.

Other case: please advise vent hole(telltale hole, We can seal welding this vent hole if code mention it or not. and what is funsion this vent?.

Thanks

 

[IFRs]

The telltale hole is doing its job. Don't weld it shut. Since you can safely do hot work, use the hole to pressurize the assembly, find the leak with soapy water or other leak testing fluid and weld up the leak. Test all the welds using the pressure. Leave the telltale hole open but plug it with heavy grease. Unless you are sure the roof plate to neck weld is bad, only repair what is leaking.

 

[sangnguyen038]

Hi IFRs,
Where is mentioned venthole, I see in api650 is not mentioned it. So that mean when finish welding reinforemend pad, We can plug by seal welding, not plug by heavy grease.

Could you clarify this venthole of rein pad of pad on roof. My thinker is no need after the air test finished. We can plug by seal welding.

 

[IFRs]

There is no requirement for a telltale hole on fixed roof fittings. It is not violating the standard to not have one or to weld up the one you have. Roof nozzle don't usually leak and if they do it is not all that bad - just water in your product or a small amount of vapors escaping into the environment. On the other hand, this test port served a purpose in this case and revealed poor workmanship that now you are going to spend money to fix. If your other roof nozzles were installed by the same contractor, you may want to give them some NDE, just in case....

 

[JStephen]

Under the current standard, certain tanks designed per F.2.4 appear to require tell-tale holes in roof nozzle. I think this is a fairly new addition/revision, so likely would not apply to an older tank.
I don't see in the above if it was ever stated if the product was flammable- if so, any hot work on a roof nozzle in-service would be a very bad idea.
Is it known if the nozzle was seal-welded on the underside? If not, the tell-tale hole may simply be a mistake in the first place, as it would inherently leak with normal top-side-only welding.
If the hole is threaded, put a plug in it.
If not, I'd suggest trying epoxy or caulking type materials. If the tank ever goes through an in-breathing cycle, do it then.
Otherwise, wait until the tank is out of service and cleaned and repair properly via welding.

 

[r6155]

If purchase order or shop drawing show telltale hole then air test is required, and telltale hole shall not be pluged. Only use grease.

Regards

 

[sangnguyen038]

thanks so much to Mr. IFRs and Jstepphen, R6155.

Thank you your discussing. Look your recommendation is helful. If case issued, should be refect on API 650 or interpretation mentioned in code.
We could based on for construction and repair.

 

[r6155]

@ sangnguyen038
Please, do not duplicate post.

https://www.eng-tips.com/threadminder.cfm?pid=286

Regards