A renewable energy provider faced significant challenges on a geothermal project due to extreme degradation in critical piping. The heat and the highly corrosive nature of the geothermal liquids present at the steam source critically reduced the anticipated life of the originally specified carbon steel steam-supply system.
Extensive research and testing prompted the plant managers to specify the replacement of the carbon steel with “Super Duplex” stainless steel pipe and Alloy 59 filler metal to achieve maximum corrosion resistance and piping-system life expectancy. Both materials have proven to be challenging to machine and weld, a factor that has limited their utilization despite superior corrosion resistance. Proper fusion of these materials requires precisely machined symmetrical weld joints, a scrupulously clean environment and a carefully tested and controlled heat input that can only be achieved with advanced computer-controlled welding equipment.
Conventional welding methods that had been previously implemented at the plant had yielded poor results in terms of low deposition rates and a high number of rejected welds. Even with extensive experience with the proposed base and filler materials, project supervisors remained highly skeptical of weld processes other than conventional GTAW, and required a definitive welding solution with consistent proven results.
Prior working experiences led to a request for Tri Tool to design a comprehensive field-machining and welding solution centered on those unique materials. In response, the company’s welding-research team developed specialized procedures leveraging the latest AdaptARC mechanized, multi-process equipment, such as the GMAW Pulsed Spray delivery platform for the exacting control of heat input required to consistently deliver 100% X-ray-qualified welds.
Weld coupons were produced in the project materials and third-party testing validated the successful implementation of welding procedures and equipment. Sixteen critical steam-supply system welds were performed on 20” O.D. x .390” wall and 24” O.D. x .435” wall Super Duplex pipe, elbows and saddle branches using Alloy 59 filler material and a GMAW-P process with dramatically higher deposition rates and reduced weld-out times relative to conventional methods—with zero defects—vastly exceeding project managers’ expectations.
In summary, the improved performance and technological and procedural advancements offered by today’s programmable, multi-process welding systems can provide major benefits for project and maintenance management. Whether working with exotic and difficult materials or implementing custom procedures for maximum efficiency and reliability, welders have an incredible level of control and unprecedented operational advantages. Their flexibility and configuration make these systems a serious consideration for maintenance or fabrication work when procedural compliance planning, dependability, quality results and increased productivity are priorities. MT
Tri Tool, Inc.
Rancho Cordova, CA