ASME B31.5-2001 pdf – REFRIGERATION PIPING AND HEATTRANSFER COMPONENTS.
527.6 Defect Repairs
All defects in welds requiring repair shall be removed by flame or arc gouging, grinding, chipping, or machining. All repair welds shall be preheated and postheated as originally required and the basic principles of the same welding procedure initially used shall be employed as far as applicable. This recognizes that the cavity of the weld may not be of the same contour or dimensions as the original joint.
Preheating may be required on certain alloy materials of the air hardening type in order to prevent surface checking or cracking adjacent to the flame or arc gouged surface.
528 BRAZING AND SOLDERING
528.1 Brazing Materials
528.1.1 Filler Metal. The filler metai used in brazing shall be a nonferrous metal or alloy having a melting point above 840°F (449°C) and below that of the metal being joined. The filler metal shall melt and flow freely with the desired temperature range and, in conjunction with a suitable flux or controlled atmosphere, shall wet and adhere to the surfaces to be joined. Brazing material containing other than residual phosphorous as an impurity is prohibited on joints made of ferrous materials.
528.1.2 Flux. Fluxes that are fluid and chemically active at the brazing temperature shall be used when necessary to prevent oxidation of the filler metal and the surfaces to be joined and to promote free flowing of the filler metal.
528.2 Brazing Preparation and Procedures
528.2.1 Surface and Joint Preparation. The surfaces to be brazed shall be clean and free of grease, oxides, paint, scale, and dirt of any kind, except as noted in para. 528.2.5. Any suitable chemical or mechanical cleaning method may be used to provide a clean wettable surface for brazing. The procedure for joints covered in para. 517 shall be as outlined in the Copper Tube Handbook, published by the Copper Development Association.
528.2.2 Joint Clearance. The clearance between surfaces to be joined shall be not greater than 0.004 in. (0.1 mm) or a diametral clearance of 0.008 in. (0.2 mm).
528.2.3 Heating. The joint shall be brought urnformly to brazing temperature in as short a time as possible to minimize oxidation.
528.2.4 Brazing Qualification The qualification of brazing procedures and brazing operators shall be in accordance with the requirements of Part QB, Articles XII and XIII, Section IX, ASME BPV Code.
528.2.5 Oil. Oil used for lubrication during mechanical expansion of tubing in coils need not be removed provided that sample(s) used for procedure qualification were in a similar condition and that the requirements of para. 528.2.4 are met.
528.3 Soldering Materials
528.3.1 Solder. The solder metal used in soldering shall be a nonferrous metal or alloy having a solidus between 400°F (204°C) and 840°F (449°C) and below that of the metal being joined. The solder shall melt and flow freely within the desired temperature range and, in conjunction with a suitable flux, ASTM B 813, shall wet and adhere to the surface to be joined.
528.3.2 Flux. Fluxes that are fluid and chemically active at the soldering temperature shall be used to prevent oxidation of the solder or filler metal and the surfaces to be joined and to promote the free flowing of the solder.
528.4 Soldering Preparation and Procedure
528.4.1 Surface Preparation. The surfaces to be soldered shall be clean and free from grease, oxides, paint, scale, and dirt of any kind. Any suitable chemical or mechanical cleaning method may be used to provide a clean wettable surface for soldering.
528.4.2 Joint Clearance. The average clearance between surfaces to be joined shall be not greater than 0.004 in. (0.1 mm), or a diametral clearance of 0.008 in. (0.20 mm).