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roca (Mechanical) (OP)
25 Feb 03 23:13
I have a an ASME VIII Divison 1 vessel which is now finished, tested and sitting at site.
However one nozzle is of an incorrect size. We need to replace this nozzle with a larger one.
Welding will be done with an approved weld procedure at site.
Welds wll be 100% Dye Penetrant tested.
My question is - do we need to re do the ASME code hydrotest as we have cut into the vessel pressure envelope.
If I were just welding a an external pipe support clip to the vessel without cutting the shell / ends then I would not apply another hydro-test
Any comments / help will be most helpful
Helpful Member!(2)  spt (Mechanical)
26 Feb 03 2:34
The removal of an existing nozzle and the installation of new nozzle is known as an alteration. If this is a new unit and the equipment owner desires the manufacturers warranty and the ASME certification to remain valid then the alteration needs to be accomplished in accordance with the NBIC (ANSI/NB-23, Part RC 1000 and RC 3000) requirements.

The accomplishment of this alteration should be under the control of a company in possession of a NB “R” stamp qualified for field alterations. At a minimum this job requires a review of Sec VIII DI, UG-36 openings in pressure vessels and UG-37 reinforcement requirements.  The alteration requirements are based on the nozzle size and location, the design pressure and temperature parameters of the pressure vessel, the nozzle and shell material types. In addition to the required hydrostatic test upon completion of the alternation, there are many other factors that need to be checked prior to commencement of this job.
aclark (Mechanical)
26 Feb 03 8:40
I agree with spt, as an alteration the hydrotest must be conducted un accordance with UG 99 of section VIII. 1.3 X MAWP.

An R-2 form must be issued and registered with National Board.
Tankman650 (Structural)
26 Feb 03 12:09
If the vessel has a U1 stamp then the amount of NDT and the question of additional hydro or R stamp will be at the descretion of your AI.
deanc (Specifier/Regulator)
26 Feb 03 13:14
Tankman650-Suggest you obtain a "Current" NBIC and update yourself. Things have changed.
jte (Mechanical)
27 Feb 03 15:31

If you wind up requiring a hydrotest, you might want to consider (and discuss with the AI) welding a pipe end cap or 2:1 head (if the nozzle is really big) on the inside of the shell at the nozzle. Use fillet welds - size them right for the longitudinal pressure and keep them below VIII-1 minimums for PWHT. If I recall correctly, a 7/16" fillet is the max you can put on without requiring a PWHT vessel to be re-PWHT.

This head on the inside of the shell at the nozzle will allow you to hydro the nozzle and its connection to the shell without having to hydro the entire vessel. After the hydrotest cut off the head and grind flush. Many AI's will accept this. Again, check with yours first.

roca (Mechanical) (OP)
27 Feb 03 19:08
Morning All - Thanks for all your useful replies.
One thing I didn't mention and perhaps should have done is that the vessel is not ASME - 'U' Stamped - only designed and fabricated in accordance with Division 1 rules. The vessel is located in a gas plant in Pakistan where there is no Authority Inspectors.
My main question is where in the ASME VIII Division 1 code does it state that when a nozzle is added to new finished and tested vessel that a new hydrotest has to be applied to it?
In my opinion we have to hydrotest however my superiors are trying to get around this. It may be that our client / end user will have the final say on this.
Thanks again
spt (Mechanical)
28 Feb 03 0:13
No where does Sec VIII Div 1 address alterations to pressure vessels in the field. Repairs and alterations to ASME B&PV after the signing of the Manufacturers Data Report are covered in the NBIC, Part RC 1000 and RC 3000. The NBIC will refer you back to the design code for the specifics, but both Sec VIII D1 (UG 99 and UG 100) and the NBIC ( RC-3030) require pressure testing.
deanc (Specifier/Regulator)
28 Feb 03 7:58
Suggest you use the NBIC as a guide. If a hydro cannot or will not be performed,you place yourself at risk. Perhaps
NDE as a minimum if you have no other choice.
69691 (Mechanical)
5 Mar 03 8:25
Since the pressure vessel is not ASME "U" stamped, it is up the manufacturer and/or owner of the vessel to come up with a solution.  My recommendation would be to hydro test the vessel if possible.  If not, when the new nozzle is being attached PT the root pass and PT or MT the cover pass.  If you use the NBIC as a guide, which is what you would be using if the vessel were "U" stamped, the NBIC allows "acceptable alternate methods of NDE" in lieu of a hydro.
danjo (Mechanical)
15 Mar 03 17:37
If I am the client I would not accept the vessel without any NDT and hydrotesting. That is my only warranty for the integrity of the vessel. I dont think any responsible inspector would certify such vessel without the required hydrotest and NDT.
WBH (Mechanical)
21 Apr 03 21:43
Personally I would hydrotest, or at least perform NDE during and after completion of welding.  If reinforcement of this nozzle is required by addition of a pad an air test could be conducted as well.

For the sake of discussion, the nozzle in question could be classified as a repair,  pending the nozzle size is not larger than any nozzle included in the original design NBIC appendix 6 B. 10.  This must be evaluated to determine if this is deemed an alteration/repair.  If considered as a repair, hydrotesting would be a optional testing method, however would not be required by the NB.  
Your example of addition of a bracket could be considered an alteration in regards to loading, and could require a hydrotest if deemed an alteration.
roca (Mechanical) (OP)
22 Apr 03 22:26
Thanks very much for all your replies
chicopee (Mechanical)
24 Apr 03 18:17
Since you are doing a major repair, NBIC requires a hydro at 150% mawp of tank. Use water within proper temperature range. Bring pressure slowly up to 150% mawp then reduce pressure to mawp for an external exam.  Dont take a short on this project.
DORU (Mechanical)
25 Apr 03 1:54
Dear Sirs,
I have the following problem.
My Client (I am a contractor) has just received a new pressure vessel (Instrument air receiver) with MAWP 8 bar. The vessel manufacturer did not wanted to weld a few attachements for sustaining a ladder but we still need these.
The vessel is primed, has 10mm thickness and was tested in the manufacturer's yard. The vessel is not ASME stamped but is
Can I weld 4 attachements for sustaining a vertical ladder ?
Where in ASME 8 can I find the rules concerning welds on vessels after delivery ? Please, can you help ?
chicopee (Mechanical)
27 Apr 03 21:59
aybee (Mechanical)
11 May 03 22:59
what material is the vessel, how thick?, what size of nozzle? what temperature/pressure does the vessel operate at, what does it contain?
aybee (Mechanical)
15 May 03 23:10
before we can make a recommendation , we need to know
material of shell, location of the new nozzle, size of the nozzle, temperature of the process, thickness of the shell,is the pressure cyclic, what is the process is it Lethal, what NDT has been done for the rest of the fabrication ...dye pen mentioned indicates not much ..if a new nozzle was added with 100% NDT it may be better than any of the others have had.
ASME are preparing a series of Post Construction codes which should prove helpfull in cases like this
ExAI (Mechanical)
2 Jun 03 22:27
Many replies in this thread are correct when they state that the ASME does not discuss changes or repairs to vessels that have already received final ASME acceptance as evidenced by a signed data report.  The cases presented add the wrinkle that they meet the ASME but are not stamped however that wrinkle has no bearing on the final answer.  Many responders have suggested that the NBIC applies.  They are only correct if the vessel is operated in a location where the jurisdiction has a pressure vessel law that imposes the NBIC as the directed means of repairs and alterations.  To be clear, the NBIC only has Repair and Alteration authority where its rules are imposed by the political authority.  Most (but not all) States here in the US have similar statements in there laws.  It is clear that these cases require repairs and/or alterations to a previously fabricated unit.  It should also be clear the the means of performing the work is under the total control of the local Jurisdictional authority only.

Lane Baker
Baker Quality Services

aybee (Mechanical)
3 Jun 03 8:09
Lane Baker is correct, The guy who started this off sounds as if he is in an area where the rules and regs in the US and the backing of a strong insurance ethic dont always apply. Sometimes the man on the spot is between a rock anda hard place got no backup from Regulatory authority and his bosses are breaking his back to come up with a cost effective solution ie dont spend money . So he tries to do the right thing by the best codes he has but needs backup...been there. Plus we are all yakking about what should be without a clear idea of the Risk..this might be a 50psi drain vessel with warm water in it 6mm thick, or it might be 500psi 5" thick with something nasty in it ...none of us knows.. nor do we know the quality of the exisiting fabrication (I have said all this before)I would be inclined to do 100% UT/RT + Mag particle(if its carbon steel)of each weld as it is done provided the Risk was low enough to be able to stand up in a court of law and say that this seemed a valid Engineering judgement..
roca (Mechanical) (OP)
3 Jun 03 20:42
Aybee - You hit the nail on the head.
The equipment has now been modified, NDE applied, has been hydro-tested and the client is happy too.
For the record the vessel details were :-
Amine Drain Tank
DP  3.5 barg / FV @ 120°C
I.Dia = 2100
Thk = 9 mm
6" NB Nozzle replaced with a 10" NB
Contents  - Amine Solution + Hydrocarbons
Thanks for all the replies  

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