Figure 5 shows a weld coupon performed by a welder during training. All weld coupons were radiographically inspected. In addition, the weld coupon was sent out for ASTM G41 corrosion testing, which also was required to yield acceptable results prior to the welder being job certified to weld on the plant’s pipe. It took, on average, two weeks for a welder to master the skill prior to taking and passing the welder qualification test. What resulted, however, was a new skillset for welders in San Diego County and a growing working relationship between the contractor and the Local. Verification and Inspection The SMO 254 pipes are critical to the process of the desalination plant. No water can be desalted with these pipes out of service. Therefore, these pipes are considered process critical, and as such, the engineer was very concerned about their reliability. In addition, the roughly 1000 lb/in.2 pressure of the pipes compelled the engineer to designate the pipes as Category M fluid service pipes per ASME B31.3, which required 100% radiographic inspection on every field weld. In addition, as recommended by the process engineer, dye-penetrant testing of the root pass was performed prior to the cold and fill passes being placed, and all welds were visually inspected to the applicable ASME code. Figures 6, 7 show dye-penetrant testing of the root pass on typical pipes at the project. The following parameters were required to be recorded during welding: • Voltage (V) • Amperage (A) • Welding length/travel distance (in.) • Welding time (s) • Shielding gas flow rate (ft3/min) • Backing gas flow rate (ft3/min) • Oxygen content (%) • Temperature (°F). The following parameters were JUNE 2016 / WELDING JOURNAL 63 Fig. 6 — Dye-penetrant testing of the root pass on a 12-in.-diameter weld on SMO 254 pipe. In this stage, the dye is first applied to the joint and allowed to dry prior to applying the developer solution. Fig. 7 — Dye-penetrant testing on the root pass of a 36-in.-diameter SMO 254 alloy pipe. In this stage, the developer is applied and the joint is inspected for defects. Fig. 8 — Welder performing a typical weld on SMO 254 pipe. The QC inspector is nearby to record relevant data and ensure compliance with WPS requirements for each weld.
Welding Journal | June 2016
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