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D.C. Municipal Regulations (Last Updated: September 13, 2017) |
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Title 12. CONSTRUCTION CODES SUPPLEMENT OF 2013 |
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SubTilte 12-E. MECHANICAL CODE SUPPLEMENT OF 2013 |
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Chapter 12-E10. BOILERS, WATER HEATERS AND PRESSURE VESSELS |
Section 12-E1021. WELDED REPAIRS ON BOILERS AND UNFIRED PRESSURE VESSELS
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Insert new Section 1021 in the Mechanical Code to read as follows:
1021.1 Crack repair in stayed areas. Cracks in stayed areas shall be allowed to be repaired by welding, provided that no multiple or star cracks radiating from rivet or stay bolt holes shall be welded.
1021.2 Crack repair in unstayed areas. Cracks in unstayed shells, drums or headers of boilers or pressure vessels shall be allowed to be repaired by welding, provided that the cracks do not extend between rivet holes in a longitudinal seam, or parallel to a longitudinal riveted seam within 8 inches (203 mm), measured from the nearest caulking edge. The total length of any one such crack shall not exceed 8 inches (203 mm). A crack of greater length shall be allowed to be welded provided the complete repair is radiographed and stress-relieved. Any crack that is allowed to be welded shall be properly prepared to permit fusion through the entire plate thickness.
1021.3 Crack repair in unstayed furnaces. Cracks of any length in unstayed furnaces shall be allowed to be welded, provided that the welds are thermally stress-relieved. Welds shall be applied from both sides of the plate wherever possible. Welds applied from one side only shall be allowed to be used if expressly permitted by the inspector. Repair of cracks by welding at the knuckle or turn of flange of furnace openings shall be prohibited except upon special prior approval by the boiler inspector.
1021.4 Corrosion repair in stayed furnaces. Corroded areas in stayed furnaces shall be allowed to be built up by welding, provided that the remaining uncorroded plate material has an average thickness of not less than 50 percent of the original plate thickness, and further provided that the areas so affected are not deemed by the inspector to be sufficiently extensive to impair the safety of the object. In cased furnaces, the stays and stay bolts shall come completely through the reinforcing metal and the original ends of the stay bolts shall be plainly visible to the inspector.
1021.5 Corrosion repair around access openings. Corroded areas around manholes or handhole openings, in either stayed or unstayed plates, shall be allowed to be built up by welding, provided that the average loss of thickness does not exceed 50 percent of the original plate thickness and that the area to be repaired does not extend more than 3 inches (76 mm) from the edge of the hole.
1021.6 Corrosion repair in unstayed shells. Corroded areas in unstayed shells, drums or headers of boilers or pressure vessels shall be allowed to be built up by welding, provided that the remaining uncorroded plate material has an average thickness of not less than 50 percent of the original plate thickness, and further provided that the inspector has deemed that the safety of the object has not been impaired.
1021.7 Repairs to connector areas. Edges of butt straps, of plate laps, of nozzles, or of connections, attached by riveting, shall be allowed to be restored to their original thickness by welding. No seal welding shall be used except upon special prior approval by the boiler inspector, and in no case shall seal welding be used where cracks are present in riveted areas.
1021.8 Welding tube ends. The ends of tubes in fire-tube and water-tube boilers shall be allowed to be welded, provided that they have not been reduced more than 10 percent in thickness and they comply with the requirements of paragraphs PWT-11 and PFT-12 in Section I, Parts PWT and PFT of the ASME Code.
1021.9 Re-ending tubes and pipes. Re-ending of piecing tubes or pipes in either fire-tube or water-tube boilers shall be permitted, provided that the thickness of the tube or pipe has not been reduced by more than 10 percent from the thickness required by the ASME Code for the approved pressure. In all cases they shall comply with the requirements in Section I, Part PWT, paragraph PWT-10, “Tube Wall Thickness” of the ASME Code.
1021.10 Patch material. The material used for patches shall be of the same general quality and have at least the same yield strength of the plate to be patched. The thickness of any patch shall be at least equal to, but not more than 1/3 inch (8.5 mm) greater than, the plate being patched.
1021.11 Permitted patches. Flush or butt-welded patches or new sections shall be allowed to be applied to stayed plates without limitation of size or plate thickness. Lapped or fillet-welded patches shall be allowed to be applied to stayed plates, provided that they are not exposed to radiant heat. Lapped and fillet-welded patches shall be allowed to be applied on the pressure side of the sheet in unstayed areas, provided that the maximum diameter of the opening so repaired does not exceed 16 times the thickness of the plate, but in no case shall the opening be larger than 8 inches (203 mm) in diameter.
1021.12 Patches not permitted. No flush or butt-welded patches shall be permitted in unstayed shells, drums or headers.
1021.13 Threaded to weld-in stays. Threaded stays shall be allowed to be replaced by welded-in stays, provided that, in the judgment of the code official or insurance company inspector, the plate adjacent to the stay bolt has not been materially weakened by deterioration or wastage. All requirements of the applicable sections of the ASME Code governing welded-in stays, including Section I, Part PW, paragraph PW-19, “Welded-in Stays” shall be met.