Telltale hole for Roof Opening repad

[wisnu11]

I was wondering why in API 650 paragraph 5.8.4 and 5.8.5 do not mention the requirement of telltale hole for the roof opening repad, either manhole or nozzle. In the Shell opening section (para. 5.7.1 to 5.7.6) it is clearly mentioned for this requirement.

However in paragraph F.7.3 (point 3.) it is mentioned that roof nozzle shall meet the requirement of 5.7.1 to 5.7.6.
Does this mean that telltale hole on repad for roof nozzle/manholes only required when there is internal pressure in the tank?

my personal opinion is that both roof and shell opening repad require a telltale hole to do the soap testing to check the integrity of the seam.

Thank you for all the response.

 

[JStephen]

On standard roof repads, the underside is not seal-welded, so there is not an enclosed space to test, thus not tell-tale hole to test it.

F.7.3 is only applicable to tanks with a certain range of pressure, not to all pressurized tanks.

 

[wisnu11]

JStephen

Thank you, however I've found many tanks where the roof nozzle repad is full seal welded and yet no telltale hole is provided.

or if rephrase, if we decide to seal weld the repad of the roof nozzle (repad to the roof plate and repad to the nozzle neck), does API 650 suggest to add a telltale holes?

 

[Duwe6]

API-650 does not require telltale holes, and they are a poor idea. There will be no process liquid pressing on the roof, so the need does not exist. There will be rain on the roof, so telltales just give you another corrosion path.

If each telltale is packed with grease, like all repad holes are supposed to be, there is minimal risk of internal corrosion. But why bother with putting useless holes in your tank?

 

[wisnu11]

Duwe6

Agree with you.
One last question. if no telltale holes provided (which mean we can not do soap test), should a simple PT to examine the weld of the repad be sufficient?

 

[Duwe6]

Wouldn't even bother with the PT; visual only. This weld on the roof is structural only. It will never be a pressure boundary weld.

 

[wisnu11]

Thank you Duwe6