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Inspection Trends - January 2011 - Winter

30 Inspection Trends / January 2011 ANNEX A-1 Carbon Steel Specifications/Preheat Preheat Requirements Specification Grade Thickness Minimum Preheat Comments ASME SA36 32°F Plate & shapes ASME SA53 Type F, S, E, (If ambient temperature Pipe welded and Grades A and B is below 32°F, seamless ASME SA105 1⁄8 to 3⁄4 in. base metal shall be Flanges and fittings ASME SA106 Grade A and B preheated and maintained Pipe, seamless ASTM A108 1015 CW, at a min. temperature of 70°F.) Bar 1018 CW, 1020 CW ASME SA134 SA283 Grades A, B, C, D >3⁄4 in. to 50°F Pipe, welded 11⁄2 in. SA285 Grades A, B, C ASME SA139 Grades A, B, C, D, E >11⁄2 in. to 150°F Pipe, welded 21⁄2 in. ASME SA178 Grades A and C Tube, ERW ASME SA179 Over 21⁄2 in. 225°F Tube, seamless ASME SA181 Class 60 Flanges and fittings ASME SA192 Tube, seamless ASME SA234 WPB Fittings ASME SA266 Class 1 Forgings ASME SA283 A, B, C, D Plate ASME SA285 A, B, C Plate ASME SA333 1, 6, 10 Pipe, seamless and welded ASME SA334 1, 6 Tube, welded ASME SA352 LCA and LCB Castings ASME SA372 A Forgings ASTM A381 Grade Y35, Y42 Pipe, welded Y48, Y46, Y50 ASME SA420 WPL6 Fittings Fig. 2 — Annex A-1 is an example of one page from an annex, and shows how an annex can be used to list the base metals and preheat requirements. Base Metals The WPS must list the base metals to be joined. Whether to list the base metal specification; the P, M, or S number; or the base metal chemistry is a decision the manufacturer has to make in conjunction with the applicable welding standard. Welding standards group the base metals together that have similar weldability. AWS D1.1 divides the carbon steel and high-strength lowalloy steels into Groups, ASME Section IX groups them by P numbers, NAVSEA uses S numbers, and AWS B2.1 uses M numbers. Base metals included in a specific grouping typically have similar chemistry and weldability. Unless impact toughness is a requirement of the applicable welding standard, all the base metals within a group can be welded with the same WPS. The WPS usually lists the group to indicate all the base metals within the group can be welded. There is one major problem with this practice. The problem is that the grouping (P #, M #, S #, etc.) is not typically stenciled on the raw material. There is no easy way for the welder (or the inspector) to know whether the WPS is applicable to the piece of raw stock in the inventory based on the material specification marked on the metal. What information is typically stenciled on the raw material and what information is not? Usually the size and material specification and grade or alloy are marked on the raw stock. For example, the welder might pick up a length of stainless pipe that is marked “ASTM A312 Type 316” along the length, but P8 is not listed anywhere. A structural wide flange beam might be marked ASTM A992, but you will not find Group II listed anywhere on the beam. What to do? How can the welder correlate the information listed on the WPS to the information marked on the raw material? One approach is to list the grouping, i.e., P# or M #, etc., on the WPS and reference an annex that contains all the applicable base metals in the same group listed by the WPS. There are other alternatives such as listing all the applicable material specifications and grades or alloys in the WPS, but that would turn the WPS into a 20-page document. Another solution is to provide the welders with their own copy of the welding standard, but to say that solution would be costly is an understatement. Including an annex with the WPS is a viable solution — Fig. 2. The annex only lists those material specifications used by the manufacturer.


Inspection Trends - January 2011 - Winter
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