Interpretation IX-17-29<\/a>.<\/p>\n\n\n\nThe exemption given in QW 202.4 for dissimilar base metal thicknesses is not required to be invoked for this situation.<\/p>\n\n\n\n
However, consider the problem further.<\/p>\n\n\n\n
Does the PQR described in above question support a WPS for groove welding between a 20 mm thick P number 8 metal welded to a 100 mm thick P number 1 metal?<\/p>\n\n\n\n
In this question, the thickness of P number 1 material falls well within the qualified range of the PQR. For P number 8 material however, the qualified range of the PQR is not enough, and the exemption given in QW 202.4 (b)(1) would need to be invoked.<\/p>\n\n\n\n
However, the exemption given in QW 202.4 (b) is applicable only for the thicker<\/em> member of the production joint. Hence, it follows that the PQR cannot be used to support the WPS in question.<\/p>\n\n\n\nConsider another variation of the question. Does the PQR described in above question support a WPS for groove welding between a 15 mm thick P number 8 metal welded to a 210 mm thick P number 1 metal?<\/p>\n\n\n\n
In this question, the thickness of P number 8 material falls well within the qualified range of the PQR. For P number 1 material however, the ordinarily qualified range of the PQR is not enough, and the exemption given in QW 202.4(b)(2) needs to be invoked.<\/p>\n\n\n\n
The situation is fit enough to get the exemption given in QW 202.4(b)(2). The thinner member of the production joint satisfies the thickness limits permitted by QW 451, and there is no limit on the thickness of the thicker member since the PQR was qualified on a base metal of thickness > 38 mm.<\/p>\n\n\n\n
Hence, it follows that the PQR can<\/em> be used to support the WPS in question.<\/p>\n\n\n\nConsider yet another variation of the question. Does the PQR described in above question support a WPS for groove welding between a 20 mm thick P number 8 metal welded to a 210 mm thick P number 1 metal?<\/p>\n\n\n\n
In this case, the thickness of neither the P8 material nor that of P1 material falls in the ordinarily qualified range of the PQR. The P1 material qualifies for the exemption given in QW 202.4(b)(2). However, the P number 8 metal falls outside the qualified range of thickness, and no exemption can be invoked to keep the PQR in contention.<\/p>\n\n\n\n
Hence, the PQR cannot be used to support the WPS in question.<\/p>\n\n\n\n
That is not all. Consider this. <\/p>\n\n\n\n
Can this PQR be used to support a WPS for groove welding between a 150 mm thick P number 8 metal welded to a 100 mm thick P number 1 metal?<\/p>\n\n\n\n
The thinner member (that is, the 100 mm thick P number 1 metal) meets the range set by QW 451.1.<\/p>\n\n\n\n
In this case, the thicker member is P number 8 metal. Hence, it has to be considered under QW 202.4(b)(1). Since the PQR was done involving thickness of 9 mm (which is more than the 6 mm specified in QW 202.4(b)(1)), it would seem that the situation is fit enough to avail the exemption given in QW 202.4 (b)(1).<\/p>\n\n\n\n
HOWEVER, the situation is NOT fit enough for the exemption. The exemption given in QW 202.4 (b)(1) is only applicable for “joints of similar P-Number materials…”. The situation here requires two base metals of dissimilar P-Number materials and dissimilar thickness.<\/p>\n\n\n\n
So, Section IX does not permit this PQR for the production joint in question, as far as base metal thickness is concerned. That is, the PQR cannot<\/em> be used to support the WPS.<\/p>\n\n\n\nReckoning Dissimilar Thicknesses When Toughness Is A Requirement<\/h2>\n\n\n\n
Consider the following problem asked in Interpretation IX-20-09.<\/p>\n\n\n\n
\u201cBackground: A single PQR with a groove weld joint was completed using a process permitted by Table QW-451.1 Note 3 with plates of two different thicknesses which were not tapered to match at the weld (dissimilar thickness). Both plates were P-No. 1 Group No. 1, with one side of the coupon comprised of a 10 mm thickness plate and the other side of the coupon comprised of a 38 mm thickness plate.<\/p>\n\n\n\n
Question (1): Will the single PQR support a WPS having a base metal qualification range of 10 mm to 200 mm when toughness testing is required?<\/p>\n\n\n\n
Question (2): Will the single PQR support a WPS having a base metal qualification range of 1.5 mm to 20 mm for one material welded to a base metal with a qualified range of 5 mm to 200 mm when toughness testing is not required?\u201d<\/p>\n\n\n\n
Consider question 1 first. The inquirer seemingly wants to know whether thickness of both<\/em> base metals of a joint can be of 10 mm to 200 mm range, when supported by the PQR in question. In this article on this website, it has been explained how the base metal thickness is to be reckoned when a procedure qualification has been made with dissimilar thickness base metals.<\/p>\n\n\n\nUsing the understanding established in the cited article, it follows that: this PQR can ordinarily support WPS having 1.5 mm to 20 mm thick base metal on one side, welded to 5 mm to unlimited thickness base metal on the other side.<\/p>\n\n\n\n
However, when notch toughness is a requirement, the supplementary essential variable QW 403.6 becomes an essential variable, and further limits the range qualified. As per QW 403.6, the lower limit of the qualified base metal thickness is 16 mm or the actual thickness qualified in test coupon (in this case 10 mm), whichever is lower.<\/p>\n\n\n\n
Hence, the qualified range of thickness would be: 10 mm to 20 mm on one side, welded to 16 mm to unlimited thickness on the other side. The range asked by the inquirer in question 1 does not fall in this range. Hence, the answer given by the committee is justifiably no.<\/p>\n\n\n\n
Consider question 2 now. As discussed above, when notch toughness is not a requirement, the qualified range of the PQR is 1.5 mm to 20 mm for the metal on one side, welded to 5 mm to unlimited on the other side. The range asked by the inquirer falls in this range. Hence, the answer to the question 2 has been given \u2018yes\u2019 by the committee.<\/p>\n\n\n\n