Essential Variables for Tube to Tubesheet Welds Defined<\/strong><\/h3>\n\n\n\nBefore the 2019 edition, the welder qualification for tube to tubesheet welds did not have any separate essential variables. Only the requirements of QW 193.2 were applicable. Additionally, a few liberties (such as \u2013 qualification can be done through a regular groove weld too if QW 193 is not invoked by the referencing code or specification) were given under QW-303.5.<\/p>\n\n\n\n
In the 2019 edition, a new paragraph QW-387 has been added. QW-387 is dedicated to the subject of welder (or welding operator) performance qualification for tubes to tubesheet welds. Some essential variables have been defined in the Table QW-388. QW 303.5 has been deleted, and the requirements therein have been merged with QW-388.<\/p>\n\n\n\n
A notable difference between the requirements for procedure qualification (as laid in QW-202.6) and those of performance qualification (as laid in QW-387) is that while a procedure can be qualified through fillet welds too (provided referencing section does not invoke QW-193), but no such option is given for performance qualifications. Surely, if a fillet weld is good enough for procedure qualification, it must be good enough for performance qualification too!<\/p>\n\n\n\n
Note<\/strong>: This anomaly has been corrected in the 2021 edition of Section IX. QW-387.1 (c )(3) has been introduced. This clause now permits the option of fillet welds for performance qualifications too.<\/p>\n\n\n\nContents of Range Qualified Column of WPQR<\/strong><\/h3>\n\n\n\nOnly the Thickness and Diameter Are Required to be Addressed in the Range Qualified Column of WPQR<\/strong><\/p>\n\n\n\nThe QW 301.4 requires that a WPQR form, under \u2018range qualified\u2019 column, only needs to address the thickness and diameter (per QW 452). Per QG-104 however, it is required to address range qualified for all<\/em> variables on a WPQR form (and not just thickness and diameter). Clearly, there is an inconsistency here. This was before 2019 edition.<\/p>\n\n\n\nIn the 2019 edition, this conflict has been removed. QG 104 has been revised to say that only the ranges of variables qualified as required by QW 301.4 need to be addressed. This clears up conflict, though; the logic here is not quite understandable.<\/p>\n\n\n\n
When one first comes across QW-301.4, one thinks that this must be a mistake. Why would Section IX give a whole format at QW-484, showing \u2018range qualified\u2019 column for all<\/em> variables, and then not require the user to address all variables, and insisting in QW-301.4 that it is enough to only address thickness and diameter (per-QW 452)?<\/p>\n\n\n\nIt does not make much sense. Why would the committee insist that deletion of backing, change in F-No, change in P-No., change in position, etc. need not be addressed in the \u2018range qualified\u2019 column? Especially after providing suitable space for it on the WPQR form!<\/p>\n\n\n\n
Surely the committee or the editorial team would have committed an oversight here.<\/p>\n\n\n\n
This notion (that the committee committed an oversight) is dispelled once we come across the Interpretation IX-89-30. The question asked and the reply given clearly establishes that the Section IX really mandates only the thickness and diameter to be addressed in the \u2018range qualified\u2019 column. Addressing the rest of the variables is at the option<\/em> of the manufacturer.<\/p>\n\n\n\nIt is curious though, the committee\u2019s intent on this.<\/p>\n\n\n\n
Anyway, be that as it may, in my opinion \u2013 it is best to address all variables under the \u2018range qualified\u2019 column. It gives a more complete picture. It makes it easier to understand and comprehend for people that are not experts in Section IX. There is no harm in addressing all variables, is there?<\/p>\n\n\n\n
Starting Date of a Welder\u2019s Continuity<\/strong><\/h3>\n\n\n\nFor a long time, there was confusion as to what is the starting date of a welder\u2019s continuity. QW-322 says that a welder\u2019s qualification remains valid for six months. But when does that date begin? From the date of completion of welding? From the date of declaration of result? Or from the date of certification by the welding engineer?<\/p>\n\n\n\n
Till 2019 edition, Section IX was silent on the issue. In my shop, we followed the KTA rules that say that the date of validity is the date of declaration of results.<\/p>\n\n\n\n
For many people it wasn\u2019t a matter of much concern. Most welder qualifications in the companies across the world are done through the volumetric NDE method. UT or RT are not time-consuming activities. So the date of completion of welding and the date of declaration of results are not far apart. However, it becomes a matter of concern when the qualification is done through the mechanical testing method.<\/p>\n\n\n\n
Mechanical testing takes time, as it involves specimen preparation, and actual testing in an appropriate lab. In some situations, the date of completion of welding and the date of declaration of results can be apart by several weeks. In such cases, there may be a difference of opinion between the manufacturer and the inspector.<\/p>\n\n\n\n
Section IX, in the 2019 edition, has removed the possibility of this difference of opinion. QW-300.1 now clearly says that a welder\u2019s \u201cqualification continuity begins from the date welding of the test piece(s) was completed…\u201d. This clears up the matter for good.<\/p>\n\n\n\n
Small Diameter Restrictions for Set-On and Set-in Nozzles<\/strong><\/h3>\n\n\n\nIf two pipes of same <\/em>diameter are being joined by a groove-weld, it is a straight forward matter to apply QW-452.3. However, the matter is not so straight-forward when two pipes of different diameter are joined. <\/p>\n\n\n\nFor example, when a nozzle or a branch pipe is joined on to a shell or run-piping or head. In such joints, should the small diameter restrictions of QW-452.3 be applied keeping the nozzle in mind? Or the shell in mind?<\/p>\n\n\n\n
This matter was not clear in the Section IX before 2019. In the 2019 edition, a revision was brought in QW-403.16.<\/p>\n\n\n\n
This paragraph tells us that when the groove weld is made with a set-on<\/em> nozzle, the small diameter restrictions should be applied keeping the nozzle O.D. in mind. And, when the groove weld is made with a set-in<\/em> nozzle, the small diameter restrictions should be applied keeping the shell O.D. in mind. This clears up the matter.<\/p>\n\n\n\nAppendix K Added<\/strong><\/h2>\n\n\n\nSection IX is referred to by many other codes, standards, specifications, contract documents, etc. Appendix K has been added to include the wording that may be used by other codes or specifications when invoking Section IX.<\/p>\n\n\n\n
Further, the optional requirements in the Section IX such as the QW 193 for tube to tube-sheet welds, supplementary essential variables becomes activated only when invoked by a referencing code, standard, specification, or a contract document, etc. This appendix includes the recommended wording that can be used in these referencing documents, such that the intent is conveyed in a \u201cclear, concise, and accurate manner.\u201d<\/p>\n\n\n\n