11.1 Repair vs. Alteration Authorization, Execution & Methods

Repair vs. Alteration Authorization, Execution & Methods

Correct classification determines who designs the work, who authorizes it, what quality controls apply, and how the completed work is documented. Classification is based on the effect of the physical change—not on cost, duration, or whether the plant calls the work maintenance.

---

1. Repair and Alteration

A repair is work necessary to restore a vessel to a condition suitable for safe operation at the intended conditions. Like-for-like replacement of a damaged pressure part, weld excavation and restoration, or an engineered buildup can be a repair when it does not introduce a design change that meets the alteration definition.

An alteration is a physical change to a pressure-retaining component that has design implications affecting pressure-containing capability beyond the scope described by existing design documents. Examples include many new nozzle installations that require reinforcement calculations, changes in geometry, and other changes to pressure-boundary design. A mere change in operating pressure or temperature without a physical change is handled through rerating rules, not automatically labeled an alteration.

The API 510 Inspector must authorize repairs and alterations before work begins, subject to permitted prior general authorization for defined routine repairs. Alterations require design involvement and approval by a Pressure Vessel Engineer. Complex repairs also need engineering input when design, service damage, metallurgy, fitness-for-service, or testing decisions exceed the inspector's role.

Jurisdictional requirements can add approvals, registration, Authorized Inspection Agency participation, or stamping. API 510 does not override law.

---

2. Repair Organization and Welding Controls

Work must be performed by a repair organization acceptable under API 510 and any jurisdictional requirements. Recognized pathways include appropriately authorized code or National Board organizations, qualified owner-user organizations, contractors acceptable to the owner-user, and organizations otherwise authorized by the jurisdiction.

Before pressure-boundary welding, verify:

• the repair or alteration plan and required engineering calculations;
• material identification and service compatibility;
• WPS support by a valid PQR and coverage of the actual variables;
• welder or welding-operator qualifications for process and production range;
• preheat, interpass, filler-metal, hydrogen, and heat-treatment controls;
• inspection hold points and required NDE;
• pressure-test plan or documented basis for an allowed alternative; and
• records needed to update the vessel file.

Alternatives to PWHT are not casual field substitutions. API 510 and PCC-2 Article 209 provide engineered pathways with material, service, procedure-qualification, heat-input, examination, and approval conditions. The selected method must be justified against the effective code text and service damage mechanisms.

---

3. PCC-2 Article 201 Butt-Welded Insert Plates

Article 201 covers removal of an unfit area and installation of a butt-welded insert in sound surrounding material. The insert must replace the full unacceptable area, and its welds must terminate in sound material. Stability and distortion must be considered while the cutout temporarily weakens the shell or head.

Material and Thickness

The insert material and weld metal must meet applicable mechanical-property and service requirements. Dissimilar material is not automatically prohibited, but compatibility with the base material, weld, environment, and thermal expansion must be evaluated. Where ASME materials are used, matching the base material P-Number is recommended.

The insert thickness should not be less than the nominal thickness of the material into which it is welded. A thinner insert requires an evaluation for the intended service under the applicable construction or post-construction rules. Edge alignment and any tapered transition must satisfy the governing code.

Corner Radius

Rectangular and square insert plates require rounded corners unless an entire shell plate is replaced. PCC-2 2022 gives thickness-based recommendations:

• less than 1/2 in. (13 mm): a smaller radius may be used as justified;
• 1/2 in. through 1 in. (13 mm through 25 mm): 3 in. (75 mm) or larger;
• greater than 1 in. (25 mm): 6 in. (150 mm) or larger.

This is not a 1-in.-or-6t formula. For a 0.75-in. rectangular insert, the Article 201 recommendation is a radius of at least 3 in.

Minimum Size and Weld Location

For non-PWHT butt-welded carbon- and low-alloy-steel insert plates, Article 201 sets minimum plate dimensions based on the lesser of 12t or 15 in., subject to its details and exceptions. Regardless of that minimum, the insert must be large enough to remove all unacceptable material and place welds in sound material.

Intersecting or closely spaced welds require special attention and examination. Where an insert weld intersects an existing butt weld, use the Article 201 geometry, angle, and examination provisions rather than inventing a universal spacing rule. Inserts containing a nozzle must also satisfy construction-code reinforcement and Article 201 separation provisions.

---

4. Fabrication, Examination, and Testing

Prepare bevels, alignment, fit-up, and welding in accordance with the approved plan and applicable construction code. Control distortion and temporary support. PWHT is performed when required by the construction code, post-construction code, or service; an allowed engineered alternative must be documented.

Article 201 does not impose one universal examination sentence for every insert. The applicable construction/post-construction code, weld location, material, geometry, and article clauses determine the examination:

• finished welded surfaces receive MT or PT when 100% volumetric RT or UT is not required;
• rounded-corner weld regions on rectangular/square inserts require at least the Article 201 spot RT/UT coverage, or the stated staged MT/PT alternative on root, intermediate fill, and completed weld;
• closely spaced or intersecting welds have additional examination provisions; and
• the referencing code or engineering plan may require more extensive volumetric examination.

If the component can be isolated and pressure testing is practical, insert welds should be pressure tested as required by the applicable post-construction code. Where a pressure test is not performed, the alternative examination and engineering basis must satisfy API 510, PCC-2, the jurisdiction, and the approved repair plan. Never assume that surface NDE alone automatically substitutes for pressure testing.

---

5. Final Inspector Review

Before acceptance, confirm classification, authorization, design basis, repair-organization qualification, material traceability, WPS/PQR/WPQ coverage, heat treatment, NDE reports, pressure-test or alternative basis, final dimensions, and vessel-file updates. A technically sound weld is not a compliant repair if design authorization or traceable documentation is missing.