Telltale holes for pressure vessel

[shailesh20]

Is Telltale hole size more that 1/4 inch NPT is acceptable for ASME Sec VIII Div I vessel?
In our one of the equipment we made the Telltale of size 1/2 inch NPT and ASME inspector is not accepting the same.
What is the problem caused if the Telltale hole size is more than 1/4 inch NPT?

 

[nickelkid]

If your repad is not thick enough you will not get enough thread engagement to seal the threads.

 

[david339933]

1/4" Max. UG-37(g)

 

[shailesh20]

David,

I know that as per code it is 1/4" max. But is there any way to accept 1/2" as practically it will not create any issue. We have also verified the reinforcement calculation with this 1/2" size.
Currently it is not possible to make the 1/4" size hole on the pad.
Please advise if you have any suggestion to come out of this.

 

[SnTMan]

See if the AI will let you thread in a bushing, and seal weld it.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[shailesh20]

Mike,

Thanks for your reply but AI refused it saying its an ASME code requirement.
Can you provide some technical backup to convince AI? It will be very much helpful.

 

[SnTMan]

shailesh20, no, no "technical" backup. It's a standard reducing pipe bushing. 1/2 NPT x 1/4 NPT. Seal weld in place. Thereby reducing your 1/2 NPT to 1/4 NPT.

Your AI have any suggestions? Or does he just say "no"?

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[DekDee]

SnTman,
With all due respect it is not the role of an AI to provide "suggestions".
It is the role of an AI to ensure it complies with the code and this clearly does not.
We have a contractor on here who has "stuffed up" and is looking for assistance in finding an "escape clause".
Good luck !
Regards,
DD

 

[SnTMan]

DekDee, due respect to you as well. Strictly speaking, you are correct, it is not the AI's role to suggest a repair. But...

IMO it is a very poor practice to simply reject one proposal after another (if this has actually happened) without giving some idea as to what might constitute an acceptable solution.

Surely there must be something other than "replace the pad" ...

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[nickelkid]

Truly unfortunate situation. My experience with AIs have been positive when problems arise. Most are helpful and can get you in the right direction.

The seal welding of a reducer appears reasonable to me, but I have never seen it or aware of any Code Cases that address this issue.

Perhaps you can suggest welding a smaller pad (with ¼ npt) on top of the existing ½” npt hole with OD larger than the ½” npt tapped hole.

 

[DekDee]

nickelkid,
Good suggestion because the contractor can actually use that.
The point I was trying to make to SnTMan was an AI is an independent authority (I have done a similar role in various parts of the world under a different title) and therefore puts himself / herself in the firing line if they "suggest" something that may come back to bite them down the track.
If the contractor stuffs up they should put forward "suggestions" to the client as part of a Concession Request and then if the client accepts it goes to the AI to ensure code compliance,
Cheers,
DD

 

[chicopee]

If it is a vessel to be stamped with a NB number, you could ask the question directly to the National Board, altho. a third party shop inspector should be able to clarify the matter.