I agree Shane... 6GR is an AWS qualification, not ASME Section IX... Now I'm not familiar with all of API's welding procedure qualifications enough to know whether or not it has a similar qualification based on the same joint configuration as a 6GR, and they use the same name, so if someone can clarify that for me and the rest of us, then please do so. ;)
A pressure vessel is a pressure vessel is a pressure vessel... Meaning: that the weld repair in question, the primary responsibility of this repair is to withstand certain operating pressures up to, and beyond the operating design limit with a certain level of engineered safety built in the design of the vessel and repair in question, and it doesn't matter which code it falls under or not...
If it fails because someone decided that it was good enough just visually without taking this into consideration of testing the weld along with verifying the soundness of the weld repair by properly developing a validated repair welding procedure which included at least one method of Non Destructive Testing which would prove that there would be no defects in the repair, and the base metal surrounding the repair prior to depositing the repair weld if the procedure was followed properly, or an acceptable amount of discontinuities within the repair welds to still be able to accept the repair by a competent welding, mechanical, petroleum engineer who understands NDT very well and/or at the very least, hydro test the vessel to prove that the repair can indeed hold and not fail to the operating pressure by testing it to a higher test pressure, then whoever it is that's doing the repair is setting themselves up for a lawsuit regardless of the amount of liability insurance they may be carrying!!! :) :) :)
In other words, if the repair fails and your customer decide to sue you for shoddy workmanship, and if the lawyers of the plaintiff can prove that you did not take the route of employing sound, best engineering practices in the repair of this vessel, then the insurance company not only will have to pay, but you also may have a real hard time in the future to buy any more insurance because the insurance company that previously covered you will drop you like a rock, and the other companies will now know about you, and either not bother to take a risk with you, or charge you up the wazoo in order for you to have any coverage at all!!! :( :( :( And that's a best case scenario especially if no one gets hurt as a result of the failure, but if somebody does??? Then you can kiss your business goodbye!!! And possibly face new living quarters if you catch me drift!!! ;)
If I were you, I would err on the side of caution and consult with a competent engineer as well as with the customer to clear up this uncertainty so that all parties are satisfied and no one gets put in a position that could potentially harm their respective future. ;)
Respectfully,
Henry