Nozzle Addition Called a Repair by the Owner
An R stamp holder is asked to modify a vertical carbon-steel pressure vessel. The nameplate shows a maximum allowable working pressure of 150 psig at 300°F, a minimum design metal temperature of 20°F, and a shell thickness of 0.75 in. The owner wants to add a 2-in. NPS instrument nozzle with a reinforcing pad and raise the maximum allowable working temperature to 350°F. The owner's engineer calls the work 'just a repair' because the 150-psig MAWP will not change, and asks the R stamp holder to weld the nozzle using an existing qualified procedure and issue a repair report. The vessel is installed in a jurisdiction that has adopted NBIC. The R stamp holder's QC manual requires design calculations and inspector review for any alteration. The shop has not yet performed a design review or notified the authorized inspector.
1. Is the nozzle addition plus temperature increase a repair or an alteration under NBIC? Explain your reasoning.
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It is an alteration. The work changes the design temperature from 300°F to 350°F and adds a new opening with reinforcement, both of which affect the pressure-retaining design. The fact that the 150-psig MAWP is not changing does not make the work a repair. NBIC distinguishes repairs from alterations by whether the work changes the item's design conditions or pressure-retaining configuration; adding a nozzle and raising the design temperature do both.
The owner's label does not control the classification. The R stamp holder must treat the job as an alteration, perform the required design calculations, and obtain authorized inspector review before proceeding. Using a repair report for alteration work would misrepresent the scope and could leave the vessel without proper design documentation.
2. What design, inspection, and documentation steps must the R stamp holder complete before returning the vessel to service?
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The shop should first perform a design review per the applicable ASME construction code for the new nozzle and reinforcement, including the effect of the higher design temperature on allowable stresses and material properties. It must confirm the existing shell thickness and reinforcement are adequate, select a qualified welding procedure and procedure qualification record, and define NDE and any required post-weld heat treatment.
The authorized inspector must review the design and hold points before welding and after examination. The shop should complete the alteration report, update the vessel records, and apply the required R stamp marking and nameplate documentation. The jurisdiction may also require notification or approval. Only after design acceptance, examination acceptance, and report completion should the vessel return to service. The shop should not rely on the existing repair procedure alone without confirming it is qualified for the new joint and thickness.
3. The owner insists on no rerating and asks the shop to issue a repair report. How should the shop respond?
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The shop should refuse to document the work as a repair. Even if the owner does not intend to change the 150-psig MAWP, the design temperature change and the new opening still require alteration evaluation. Issuing an R-1 repair report would conceal the real scope and bypass the design and inspector review required for an alteration.
The shop can offer alternatives: complete the alteration properly with design calculations and an alteration report, or revise the scope so it truly remains a repair, if that is possible. For example, if the owner drops the temperature increase and the nozzle addition still changes the pressure-retaining configuration, the work may still be an alteration. The shop should explain the compliance risk to the owner and involve the authorized inspector and jurisdiction before any weld is made. A customer instruction cannot override NBIC requirements.