By K. Erickson and A. Moore The Answer Is The Society is not responsible for any statements made or opinion expressed herein. Data and information developed by the authors are for specific informational purposes only and are not intended for use without independent, substantiating investigation on the part of potential users. Q: What are the primary test result differences in WPS qualification of reduced-section tension tests between AWS D1.1, Structural Welding Code — Steel, and ASME Boiler and Pressure Vessel Code (BPVC), Section IX? A: (from K. Erickson) Both AWS D1.1 and ASME BPVC, Section IX, provide specific information relative to the dimensioning of the weld samples prior to testing, but there are some minor differences when evaluating the test results. AWS D1.1 simply states that the tensile strength of the base metal cannot be less than the minimum specified tensile range of the base metal used for testing. The base metal tensile strengths are listed in AWS D1.1, Table 2.1. The ASME criteria are more detailed regarding both the material type(s) and the temperature, also the material P-Number type, and thickness have to be considered. One key difference is that ASME does permit accepting tensile values less than the specified tensile strength of up to 5%, provided the specimen breaks either in the base metal outside the weld or in the weld interface location. Before qualifying any weld procedure, it is imperative that the correct base materials are confirmed coupled with the proper filler metal to be used. A questionable situation would be to weld standard A106 Grade C pipe using a minimum tensile strength of 70 ksi with E6010 (60 ksi) filler metal. Although it is possible that the filler metal strength, if welded properly, could exceed 70 ksi in tensile value, it is only classified for 60 ksi, which is less than the tensile strength of the base material used. Q: I have three questions regarding working with the ASME Boiler and Pressure Vessel Code (BPVC). We are constructing a large project that requires us to meet ASME B31.3. The fluid service is classified as High Pressure by the owner. The project involves several contractors, each is responsible for different parts of the project. The prime contractor is doing the welding on site. The prime contractor has subcontracted a portion of the work to a sub-tier contractor who is also welding onsite. The sub-tier contractor has subcontracted some of the off-site work to a different contractor who is responsible for the fabrication of skids that are packaged units consisting of filters, piping, electric motors and pumps, and the connecting piping and valves. My questions are: 1. Can the on-site contractors utilize the same qualified welding procedures submitted by the sub-tier contractor who is assembling the skids in a shop? 2. If the contractors onsite are not permitted to use the WPSs submitted by the skid manufacturer, can they pool their resources to have a third party qualify the WPSs so they can both use the same WPSs on site? 3. Can the on-site contractors, i.e., both the prime contractor and the subcontractor, send their welders to a third-party testing company to qualify and certify their welders? A: (from A. Moore) You have an interesting situation that is not unique. As a general principle, the ASME requires each contractor to qualify and certify both the WPSs and the welders. The ASME BPVC is comprised of several sections, each addresses different aspects of design, materials selection, fabrication, and inspection. The sections are interrelated, that is to say, no one section is self-sustaining. The construction codes, that is Section I for Power Boilers, Section III for Nuclear Construction, Section VIII for Unfired Pressure Vessels, etc., refer to other sections of the code to provide specific details on the subjects of materials of construction (Section II), nondestructive testing (Section V), and the qualification and certification of welding and brazing procedures and welders and brazers (Section IX). The interesting thing about working to ASME requirements is one must never forget that the construction code can and often does modify or take exceptions to Section V and Section IX. Back to my earlier statement: each contractor is “always” required to qualify and certify his or her own welding procedure specifications (WPS) by testing. That statement is true. The WPS is qualified by welding a typical groove detail. The welding variables used to weld the test coupon and the test results are recorded in a document called the PQR. So far, so good. The conditions and requirements of how to qualify the WPS are delineated in ASME BPVC, Section IX. Article V of Section IX includes an “exception” to the statement I just made. Article V lists several Standard Welding Procedure Specifications (SWPs) that can be purchased from AWS. The SWPS are exempt from the tests required in Article I and Article II of Section IX. There is a condition attached to using a SWP; basically, the contractor qualifies a welder who follows the SWPS to demonstrate they can implement the SWPS. Now, going back to the project you are working on. You state the project specification specifies ASME B31.3 and the fluid service is High Pressure. High Pressure Fluid Service invokes specific requirements on the contractor regarding the design, materials of construction, fabrication, and inspection. Where B31.3 allows the use of certain SWPSs that are listed in Section IX, Article V: B31.3 for High Pressure Fluid Service does not allow them to be used. The chapter specifically states that each contractor must “always” qualify the WPSs used for construction. The only part of the qualification effort the contractor can subcontract is the nondestructive testing and mechanical testing. — continued on page 30 Inspection Trends / Spring 2013 27
Inspection Trends | April 2013
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