ASME VIII - Avoid hydrotest on port drilling 1

[BRH100]

I intend to drill two small holes and NPT tap into a pressure vessel. If I can prove that there is sufficient material around the hole as reinforcement, do I need to repeat the hydro-test. I'm asking because it will be difficult to do so. Has anyone done this before?

 

[XL83NL]

Hydrotests are done all the time, so I think 'theyre not a difficult event to pass'.
First do the calcs. If OK: drill and tap. Then hydro. Period.

 

[JohnGP]

API 510 is the applicable code governing alterations (and repairs, reratings) of ASME VIII vessels. If it can be demonstrated that reinforcement is not required for your tapped holes, then API 510 doesn't consider them to be alterations, so I guess that means no hydrotest would be required. Best to check with your AI though.
Cheers,
John

 

[jte]

Hydrotests are done all the time, so I think 'theyre not a difficult event to pass'.
First do the calcs. If OK: drill and tap. Then hydro. Period.

It is not often a question of fear that a vessel will not pass a hydro. Most often, vessels of more than a nominal size require more than a nominal volume of water. This leads to various concerns:

Can the vessel withstand a hydrotest? Many vessels are shop hydro'd in the horizontal position in a shop. Once vertical on their foundations, the hydrostatic head can overstress the lower sections of the vessel.

Is the skirt (or saddles) capable of carrying the weight of the vessel while full of water? Many are designed for a few feet of liquid, but the majority of the vessel is in vapor service.

Is the foundation capable of supporting the weight of the vessel while full of water? I've seen plenty which are not.

Can a sufficient amount of water be warmed up to 20°F above MDMT for the vessel? This usually requires a bit more than a residential water heater.

How will the (now oily) water be disposed of post-hydrotest? We have now turned ordinary water into a hazardous material by mixing it with all the crud in the vessel.


So, I beg to differ with the opinion that all repairs and alterations to all vessels shall be hydrotested. Period. It just isn't realistic in my industry.

 

[XL83NL]

Jte, my post was meant to be slightly sarcastic, but maybe that wasnt necessary/fair. I just happenend to have such a moment.
Furthermore I was understand the impression the question for a new vessel, not for alteration.

I now see the point, your concerns are right, though I never been in such situations.
However I cant see why it should not be good engineering practice to ask the questions you posted upfront, during the initial/originaliteit engineering of the vessel.

 

[racookpe1978]

Verify with your inspector (certifying agency), but consider the following.

Your "new" material in the new pipe and instruments and its "new" pressure boundary MUST be hydro tested (1.5 Max Allowed Working Pressure).

But you do not have to hydro this new piping string and its instruments on the PV. Do that hydro test on the bench to 1.5 MAWP, then assemble the piping string into the NPT threads on the tank (it has already passed the hydro test sometime in the past) and then just do an operational test (1.0 operating pressure) on the final joint. As long as ALL of the new joints and material in the new string have met the 1.5 MAWP criteria, the new material has been tested.

In this kind of case, the final joint (NPT in your case, most often it is a flange) must be a mechanical one not a welded joint.