Study on the Long-term Operating Behaviour of Alloy Pipes and Forgings for Future High-efficiency Power Plants

Project Number 321

In this project, a test facility will be constructed especially suited to assess fatigue of safety- and operation-relevant components. Moreover, to determine the failure safety margin, current and future findings from parallel research projects (COORETEC, MARCKO700) on damage development as well as related characteristic values and material laws are to be validated by field trial.

The test facility, which has been designed for installation in a power plant of Großkraftwerke Mannheim AG, comprises a superheater test section which is located within the boiler and has a temperature of up to 725 °C as well as components of two turbine and creep test sections which are located outside the boiler and have a temperature of 630 and 725 °C, respectively. The study focuses on a temperature of 725 °C. However, the 630 °C sections can also make an important contribution as a better understanding of steel behaviour at 630 °C will help to minimise the use of expensive nickel-based materials:

  • The superheater test section is used to measure the metal temperature of the materials used to assess their influence on the corrosion and oxidation behaviour on the steam side. The section is designed for 200,000 hours. At the end of the project period, samples are to be taken.
  • The creep test sections have pipe sections installed which are subjected to internal pressure so as to result in failure after 50,000 hours. The wall strength is adapted to this objective. Adequate tools and calculations ensure that the pipe sections will be removed before failure. Operation is accompanied by parallel or running ahead creep tests. At the end of the project, samples are taken and subjected to a metallographic test.
  • The turbine test sections consist of one pipe each of a major diameter in which small plates made of turbine and boiler materials are exposed to the steam flow. This is to investigate the oxidation strength of the steam turbine materials. It is planned to change sample materials during operation.

The range of materials used (incl. coatings) extends from ferritic materials through to nickel-based alloys (T24, T92, VM12, Tempaloy AA1 SB, NF709, NF709R, HR3C, DMV310N, Tempaloy A3, Sanicro25, Mod. HR6W, S304H SB, DMV304HCU SB, Alloy617 mod., Alloy 740, XA704 Mod. SAVE12, Sumitomo New 18/8 Stainless Steel, Sumitomo New Ni Alloy, P92, FB2, CB2, St17/13W, coatings on 9 %Cr steels and Ni-base alloys).

Moreover, in terms of availability, valves and fittings are tested for internal and external tightness as well as operability of components. With regard to the high-pressure bypass system with a steam velocity higher than in a conventional bypass system it is of special interest to determine the erosion behaviour of the Alloy 617.

Within the framework of the project, maintenance and testing strategies are to be developed for the 700 °C power plant.

The project, which was started in January 2008, is scheduled to end in 2015. Four partners are responsible for project management:

  • Großkraftwerk Mannheim AG (responsible: Klaus Metzger),
  • Materialprüfungsanstalt Universität Stuttgart (responsible: Prof. Dr. Karl Maile),
  • Alstom Power Systems GmbH (responsible: Dr. Qiurong Chen),
  • EnBW Kraftwerke AG (responsible: Dr. Jörg M. Bareiß).

Other companies involved in project work are ABB AG, Bopp & Reuther Sicherheits- und Regelarmaturen GmbH, Burgmann Industries GmbH & Co KG, BHR Hochdruck-Rohrleitungsbau GmbH, KSB AG, Schweißtechnische Lehr- und Versuchsanstalt Mannheim GmbH, TÜV SÜD Industrie Service GmbH and Welland & Tuxhorn AG.

The project is co-financed by the German Federal Ministry of Economics to a considerable extent (grant no. 0327799). Industry mainly contributes its own work and services. GKM, EnBW, MVV, Kraftanlagen München and VGB participate in the financing.

With the Chairman of the VGB Technical Committee Materials and Quality Supervision being one of the four project managers, a close link between the project work and the VGB is ensured. In addition, the VGB Office provides support to project management regarding the organisation of workshops and publications.