| Abstract: | The technology of manufacture of live steam lines and hot reheat lines at FINOW Rohrsysteme GmbH are discussed. These pipelines are designed for high-performance CCGT units and are made from high-chromium martensitic steel X10CrMoVNb9-1 (P91). The principles of certification and evaluation of conformance of thermal and mechanical equipment made from new construction materials with the TRCU 032-2013 technical regulation of the Customs Union are detailed. The requirements outlined in Russian and international regulatory documents regarding the manufacture of pipes and semifinished products for pipeline systems are compared. The characteristic features of high-chromium martensitic steel, which define the requirements for its heat treatment and welding, are outlined. The methodology and the results of a comprehensive analysis of metal of pipes, fittings, and weld joints of steam lines are presented. It is demonstrated that the short-term mechanical properties of metal (P91 steel) of pipes, bends, and weld joints meet the requirements of European standards and Russian technical specifications. The experimental data on long-term strength of metal of pipes from a live steam line virtually match the corresponding reference curve from the European standard, while certain experimental points for metal of bends of this steam line and metal of pipes and bends from a hot reheat line lie below the reference curve, but they definitely stay within the qualifying (20%) interval of the scatter band. The presence of a weakened layer in the heat-affected zone of weld joints of steel P91 is established. It is shown that the properties of this zone govern the short-term and long-term strength of weld joints in general. The results of synthesis and analysis of research data support the notion that the certification testing of steam lines and other equipment made from chromium steels should necessarily involve the determination of long-term strength parameters. |
