Commercialization and Application
Metrode Products Ltd., an English manufacturer of welding consumables, has commercialized EPRI P87 (Figure 3). Although P87 can be used in retrofit applications, one of Metrode’s first sales of the filler metal was for a new plant application. The company sold about 1,500 pounds of the filler metal in shielded metal arc welding form to Babcock and Wilcox (B&W) for construction of Unit 1 of American Electric Power’s (AEP’s) John W. Turk, Jr. Power Plant, a 600-MW baseload plant near Texarkana, Arkansas, and the first ultrasupercritical (USC) pulverized coal plant in the U.S. (See page 34 for an artist’s depiction of the completed plant and a detailed description of Turk’s steam turbine design.)
3. EPRI P87 filler metal. This is the commercial version of P87, manufactured by Metrode Products Ltd. Courtesy: EPRI
B&W was contracted for the engineering, design, supply, and installation of a 600-MW net pulverized coal – fired spiral-wound universal pressure boiler. USC plants are designed to operate with overall plant heat-to-electricity conversion efficiencies that are higher than those of supercritical plants. To achieve these efficiencies, USC plants operate at higher temperatures; in the case of the Turk Plant, the design calls for a main steam condition temperature of 1,110F at 3,675 psig and a reheat steam condition temperature of 1,125F at 775 psi.
These higher temperatures pose challenges for the DMWs in the tubes of a USC boiler. For this application, the P87 filler metal was used because it allows the design to increase the temperature use limits for the DMWs between the Grade 91 and 92 alloys and the austenitic stainless steels above the boiler roof line. With the P87 filler metal, the operating temperature of the DMWs can be increased, while the inherent joint stresses can be maintained at values similar to those of the traditional Inco Weld A/182 DMWs used at lower operating temperatures.
Fabrication of the boiler pressure parts for the Turk plant has been completed, and the parts are being delivered to the plant site for erection. The plant is under construction, and major foundations are being installed. Figure 4 shows sample welds using P87. These DMWs also used the EPRI modified 60-degree weld prep angle, on the Grade 91 side of the joint.
4. Sample welds. Sample welds made with P87 filler metal using the modified EPRI weld prep. Courtesy: B&W
Future Work
The P87 filler metal used for the Turk plant was supplied as shielded metal arc electrodes. Work is ongoing between EPRI and B&W on the development of a solid wire form of P87; a prototype has been tested in trial welds, but the material has not been commercialized. A solid wire P87 would allow the filler metal to be used in gas metal arc welding (also called metal inert gas welding) and gas tungsten arc welding (also called tungsten inert gas welding). Use in these other welding processes would increase applications of the filler metal.
——Kent Coleman (kcoleman@epri.com) manages EPRI’s Boiler Life and Availability Improvement Program. John Hainsworth (jhainsworth@babcock.com) is a technical consultant with Babcock & Wilcox in Materials and Manufacturing Technology.
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