{"id":2772,"date":"2022-12-07T02:23:51","date_gmt":"2022-12-07T02:23:51","guid":{"rendered":"https:\/\/mewelding.com\/?p=2772"},"modified":"2023-02-15T02:00:51","modified_gmt":"2023-02-15T02:00:51","slug":"essential-variables-for-welder-qualification-2","status":"publish","type":"post","link":"https:\/\/mewelding.com\/essential-variables-for-welder-qualification-2\/","title":{"rendered":"Essential Variables for Welder Qualification"},"content":{"rendered":"\n
When a welder is qualified in accordance with ASME BPVC Section IX, he is only eligible to weld within the qualified ranges of the variables followed in his qualification test coupon. The qualified ranges of only a few variables<\/em> (that are laid out under QW-350 in Article III of Section IX) need to be reckoned. These variables are called essential variables<\/strong>.<\/p>\n\n\n\n If, due to job requirements, the welder is required to weld outside the qualified range of these essential variables, then he must requalify<\/strong>. A fresh qualification must be done with the changed values of these variables.<\/p>\n\n\n\n In simple words, the Section IX reckons that these variables are associated with the skill<\/em> of a welder. So, if a change occurs in these variables, the welder must prove his competence again<\/span> by taking a fresh qualification coupon.<\/p>\n\n\n\n The essential variables are different for each welding process. They are established under QW-350 for welders, and QW-360 for welding operators. It is to be understood that the variables under QW-350 and QW-360 are mutually exclusive; the variables under QW-350 do not apply to welding operators qualified using the variables of QW-360 (this finds further confirmation in interpretation IX-17-89), and vice-versa.<\/p>\n\n\n\n The table QW-416 summarizes essential variables for performance qualification of welders <\/em>with processes. This table serves as a convenience for reference.<\/p>\n\n\n\n In this article, we shall discuss the essential variables for welder qualification, when SMAW process is used<\/em>:<\/p>\n\n\n\n Per QW-402.4, deletion of backing<\/strong> is an essential variable. This means that if the welder welded with<\/em><\/strong> backing on his qualification coupon, he is only qualified to weld with<\/em> backing in production.<\/p>\n\n\n\n However, if he welded without<\/strong> backing on his qualification coupon, he is qualified to weld both with and without<\/em> backing in production.<\/p>\n\n\n\n This tells us that welding without backing is a greater skill. A welder qualified without backing can weld jobs both with and without backing.<\/p>\n\n\n\n Double welded grooves are considered welds with backing<\/strong>.<\/p>\n\n\n\n The following table explains this information in brief:<\/p>\n\n\n Here<\/a> is an article, that explains the subject of backing for welder qualification in greater detail.<\/p>\n\n\n\n Change in outer diameter<\/strong> is another essential variable for welder qualifications. This is addressed in QW-403.16.<\/p>\n\n\n\n When welding on pipes of small diameter, it takes greater skill<\/strong> for the welder to make a good weld. What is small diameter, one might ask. The answer to this is found in table QW-452.3, reproduced below:<\/p>\n\n\n\n This table tells us the following information:<\/p>\n\n\n\n If a welder welded on a pipe of any OD less than 1 inch (25 mm) in test coupon, he is qualified to weld on pipes of OD equaling the actual OD of pipe welded to unlimited OD<\/strong> in production welding.<\/p>\n\n\n\n Also, if he welded on a pipe of any OD between 1 inch (25 mm) to 2-7\/8 (73 mm) in test coupon, he is qualified to weld on pipes of OD 1 inch (25 mm) to unlimited OD<\/strong> in production welding.<\/p>\n\n\n\n Also, if he welded on a pipe of any OD exceeding 2-7\/8 (73 mm) in test coupon, he is qualified to weld on all pipes of OD 2-7\/8 (73 mm) and greater<\/strong>, in production welding.<\/p>\n\n\n\n Table QW-452.3 is applicable when the coupon is a groove weld. Same rules apply when the test coupon is a fillet weld too, these are given in Table QW-452.4 (which makes one think, why the need for a separate table in QW-452.4 when all information is identical to QW-452.3?).<\/p>\n\n\n\n There are some exemptions available to this rule.<\/p>\n\n\n\n When a welder is qualified through a groove weld coupon, he gets qualified for all diameters<\/strong><\/span><\/em> (and all fillet sizes, and all base metal thicknesses). This exemption has been given at QW-452.6.<\/p>\n\n\n\n Another exemption is for corrosion resistant & hard facing overlays. When an overlay is deposited on a pipe OD such that the direction of welding is in axial<\/strong> direction, then the small diameter restrictions as described above do not apply<\/strong>.<\/p>\n\n\n\n Note that there is no restriction on the maximum<\/em> qualified diameter; there is restriction only on the minimum<\/em> qualified diameter. Also, there is no restriction on inner<\/em> diameter of a pipe; there is restriction only on the outer<\/em> diameter.<\/p>\n\n\n\n Here<\/a> is an interesting article on this website that addresses the subject of welder qualification for pipe welding.<\/p>\n\n\n\n Change in P-number of the base metal<\/strong> is another essential variable for welder performance qualifications. This has been described in QW-403.18. However, there is wide-ranging liberty<\/em> available to this rule. The QW-403.18 refers us to table QW-423. This table is reproduced below for reference:<\/p>\n\n\n\n As can be seen, when any base metal shown in the left column in this table is used for welder qualification, he gets qualified to weld all combinations <\/strong>of base metals shown in the right column, including unassigned metals<\/strong> of similar chemical composition to these metals. As is obvious, this is a wide-ranging liberty.<\/p>\n\n\n\n1. Deletion of Backing<\/strong><\/h2>\n\n\n\n
2.<\/strong> Change in Outer Diameter of Pipe<\/strong><\/h2>\n\n\n\n
OD of the test coupon<\/strong><\/td> OD qualified<\/strong><\/td><\/tr> Less than 1 in. (25 mm)<\/td> Size welded to unlimited<\/td><\/tr> 1 in. (25 mm) to 2-7\/8 in. (73 mm)<\/td> 1 in. (25 mm) to unlimited<\/td><\/tr> Over 2-7\/8 in. (73 mm)<\/td> 2-7\/8 in. (73 mm) to unlimited.<\/td><\/tr><\/tbody><\/table> 3. Change in P-Number<\/strong><\/h2>\n\n\n\n