Re-Hydrotesting a Pressure Vessel 1

[sethevans]

If anyone can help me find this in the ASME Sec. VIII Div. 1 Code, I would greatly appreciate it.

I have a pressure vessel that was tested, and signed off. The vessel is now with our customer. Our customer supplied the calculations and drawings for fabrication.

One of the openings in the vessel was a 2.00" OD hole that was bored through the vessel wall to accomidate a flange for a future piece of equipment, (which we never had).

The customer was installing the piece and found that the hole was 0.34" too small. They were worried about grinding the excess out in order for it to fit.

I re-assured them that it would be fine as long as they were not using a flame-cutting device to do it. They, understandibly, want to make sure that this is OK.

Can anyone tell me where to find it in the code?

I greatly appreciate any responses. I'm very new at this.

 

[metengr]

sethevans;
If the vessel has already been hydotested and stamped by an AI, it is completed with regards to the ASME B&PV Code requirements.

Any work performed in the field to the vessel is now under the NBIC. In this case, you are enlarging an opening, as long as the vessel cals support an increased opening and no welding is required, this is permitted. If welding is required, you need to determine if this is an alteration or repair.

 

[sethevans]

metengr;
Thank you for your response.
The vessel was stamped by an AI, and I understand that repairs are under the jurisdiction of the NBIC.

My customer wants "a paragraph" from the code that says it's OK. The calculations do support the bigger opening.

I gave them UG-99(a), and they are worried about the term "cosmetic grinding". He's thinking it is considered a repair, but I can't find a paragraph that will ease his mind.

Again, thanks for the help.

 

[metengr]

sethevans;
The NBIC only addresses weld repairs to a pressure retaining item, and alterations, where no physical work is performed.

In this case, if the opening is made larger (physical work is performed) and no subsequent welding is required to weld a nozzle or other fitting to this opening, and the calcs show that no reinforcement is required as a result of making an existing opening larger, you are good to go. The NBIC references the original code of construction for guidance concerning design, welding and NDT to a pressure retaining item.

 

[metengr]

sethevans;

The NBIC only addresses weld repairs to a pressure retaining item, and alterations, where no physical work is performed.

Clarification and not to confuse you, in my statement above alteration can be performed with and without physical work. The way I worded it above in my post could be confusing to you as implying only alterations are done with no physical work (like re-rating the nameplate of a vessel using calculations without welding).

 

[sethevans]

metengr;

Thanks for all your help. This information should put my customer at ease.

 

[unclesyd]

Another way to look at this that if the original calculations supplied by the owner showed that a 2.00" hole was OK then a 2.00" hole minus the 0.34" would also be OK. If you brought the undersize hole up the original design intent and calculations there is no problem.

As posted by metengr make sure the installation of the flange is defined by your AI along with the requirements for inspection and/or testing.

Just a question, how was the vessel hydrotested with a hole in the shell?

 

[doct9960]

sethevans,

One of the openings in the vessel was a 2.00" OD hole that was bored through the vessel wall to accomidate a flange for a future piece of equipment, (which we never had).

The customer was installing the piece and found that the hole was 0.34" too small. They were worried about grinding the excess out in order for it to fit.

What kind of special "flange" is your customer planning to install?

 

[sethevans]

unclesyd;

the hole was bored through a boss(which was welded to the vessel) and the vessel wall. There were 4 holes drilled and tapped on top of the boss to accomidate the future flange. We had a flange machined for that boss specifically for hydro.

doct9960;

the flange is part of a camera that bolts onto the vessel in order to record what happens in the vessel. That's about all I can say. And like I said, we never had that piece of equipment to make sure that it would fit.

Thanks again to everyone for the help.

 

[unclesyd]

Thanks for the clarification of your problem being a studding outlet.

My last encounter with same is similar to yours with the exception that the hole was undersized and after machining it was oversize by about the same amount. Had to build up the bore and remachine.