Search Results for ultrasonic measurements

Both non-destructive and traditional microsectioning techniques have been used to measure the oxide thickness of steam grown oxides between two close contacting surfaces. Different power plant materials, nickel based alloys and ferritic-martensitic steels, were exposed to steam oxidation at temperatures ranging from 650 °C up to 750 °C and periods from 500 h to 3000 h. Ultrasonic measurements of thickness, based on the speed of sound in the oxide, were performed and compared to optical thickness measurements based on conventional metallographic microsectioning with promising results. Improvements on the measurement resolution have been practically demonstrated with oxides down to 65 μm thickness being measured successfully.

This study evaluates various nondestructive testing methods for detecting creep damage and assessing residual life in Grade 91 steel welds. Three primary detection techniques were investigated: phased array ultrasonic testing (PAUT), eddy current testing with high-temperature superconductor direct current and superconducting quantum interference device (ECT•HTS-dc-SQUID), and replica observation. PAUT detected creep damage between 60-80% of creep life, while ECT•HTS-dc-SQUID showed detection capability between 80-90% of creep life. Replica observation revealed creep voids only in the final stages before rupture. Additionally, three strain measurement methods were evaluated: capacitive strain sensors (providing continuous monitoring during creep exposure), laser displacement meters (used during test interruptions), and SPICA strain measurement. Both capacitive sensors and laser meters produced results comparable to conventional extensometer measurements. The SPICA method proved particularly effective in measuring heat-affected zone (HAZ) strain after creep exposure, revealing higher strain values in the HAZ compared to base and weld metal, with a consistent increase during creep exposure.

This paper discusses the design of a prototype for accurately inspecting the degree of wall thinning in boiler tubes, which plays a critical role in power plants. The environment in power plants is characterized by extreme conditions such as high temperatures, high pressure, and ultrafine dust (carbides), making the maintenance and inspection of boiler tubes highly complex. As boiler tubes are key components that deliver high-temperature steam, their condition critically affects the efficiency and safety of the power plant. Therefore, it is essential to accurately measure and manage the wall thinning of boiler tubes.

Nuclear reactor inspections occasionally identify degraded materials in irradiated reactor components. Although mechanical repair options are possible, these repair solutions may be cost prohibitive or impractical to implement due to access restraints and/or the severity of the degradation. Welding repair of reactor components may input excessive heat into these irradiated materials resulting in diffusion of trace amounts of helium within the grain boundaries of the weld heat-affected zone (HAZ). Intergranular HAZ cracking can then result from the combination of this helium diffusion and high localized tensile stresses generated during weld cooling. It is therefore critical to characterize these zones and understand limitations for welding highly irradiated components to prevent helium-induced cracking. To accomplish this, typical reactor structural materials including Types 304L and 316L stainless steels and nickel-based Alloy 600/182 materials irradiated within the High Flux Isotope Reactor facility at Oak Ridge National Laboratory were used in this study for welding and evaluation. A phased array ultrasonic inspection system has been developed to characterize cracking in the weld samples. It provides remote controlled scanning and minimizes handling the samples, minimizing operator dose. The samples are inspected from the side opposite of the welds. The material and weld grain noise were evaluated at 10 MHz and found to be conducive to detecting cracking in the material and welds. Inspection of the samples comprises a 10 MHz phased array probe sweeping a focused longitudinal wave from -60° to 60° while the probe is raster scanned over the sample in small increments. The collected data is analyzed using UltraVision 3. Several of the irradiated samples were inspected prior to welding. Some of the samples had what appear to be small lamination defects in them. One irradiated welded sample has been tested to date with no cracking detected, which has been confirmed by destructive examination.

Structural alloy corrosion is a major concern for the design and operation of supercritical carbon dioxide (sCO 2 ) power cycles. Looking towards the future of sCO 2 system development, the ability to measure real-time alloy corrosion would be invaluable to informing operation and maintenance of these systems. Sandia has recently explored methods available for in-situ alloy corrosion monitoring. Electrical resistance (ER) was chosen for initial tests due the operational simplicity and commercial availability. A series of long duration (>1000 hours) experiments have recently been completed at a range of temperatures (400-700°C) using ER probes made from four important structural alloys (C1010 Carbon Steel, 410ss, 304L, 316L) being considered for sCO 2 systems. Results from these tests are presented, including correlations between the probe measured corrosion rate to that for witness coupons of the same alloys.

The trial production of FENIX-700 turbine rotors for advanced-ultra super critical (A-USC) power generation was conducted, and their microstructure, tensile, impact, and creep properties were evaluated. Two 10-ton class trial forgings were successfully produced through double melting of VIM and ESR and free forging with a 14,000 ton hydraulic press. For examining the effect of the forging condition on the microstructure of the rotors, we adopted lower finish temperatures and an increased forging ratio on the last forging for the second trial. The grains of the second trial forging were refined by changing the forging condition. In particular, the grain size of the center of the rotor was remarkably decreased from the grain size number 0.5 to 2.8. Grain refinement improved the permeability of the ultrasonic wave in the ultrasonic inspection test, resulting in decreasing the minimum detectable flaw size (MDFS). The ductility and toughness were also improved by grain refinement. Although the grain size was decreased, the time to rupture in the creep test at 700 °C was comparable to the previous results of FENIX-700, and the estimated 105 h rupture stress at 700 °C was sufficiently higher than 100 MPa. However, it was clarified that the particles of gamma-prime in the center of the rotor had been coarsened due to the mass effect. The slight decrease of 0.2% proof stress and shortening of creep rupture time at 700 °C were attributed to the coarse gamma-prime particles. The results of the present trial expressly demonstrated that it is possible to manufacture 10-ton class A-USC turbine rotors of FENIX-700 with excellent mechanical properties and good permeability of the ultrasonic wave.

Monoblock low-pressure (LP) turbine rotor shaft forgings for nuclear power plants have been produced from up to 600 ton ingots. However, ingots greater than 600 tons are necessary to increase the generator capacity. Segregation, non-metallic inclusions, and micro porosities inevitably increase with the increase in ingot size. Manufacturing such massive ingots with high soundness is quite difficult. Thus, the development of 650 ton ingot production was carried out in 2010. The 650 ton ingot was dissected and investigated to verify its internal quality. The internal quality of the 650 ton ingot was found to be equal to that of 600 ton ingots. Subsequently, in 2011, we produced a 670 ton ingot, the world’s largest, to produce a trial LP rotor shaft forging with a diameter of 3,200 mm. Results show that the internal quality, mechanical properties, and heat stability are the same as LP rotor shaft forgings made from 600 ton ingots.

The global transition toward high-efficiency steam power plants demands increasingly advanced steel rotor forgings capable of operating at temperatures of 600°C and above. The European Cost program has been instrumental in developing creep-resistant 10%-chromium steels for these critical applications, with Steel Cost E emerging as a prominent material now widely utilized in steam turbine shafts and experiencing significant market growth. Saarschmiede has pioneered a robust, fail-safe manufacturing procedure for Cost E rotors, establishing a comprehensive database of mechanical properties and long-term performance data that enhances turbine design reliability. The company has expanded its manufacturing capabilities to include Cost F rotor forgings for high-pressure and intermediate-pressure turbines, with component weights reaching up to 44 tonnes. Investigating methods to further increase application temperatures, researchers within the Cost program discovered the potential benefits of boron additions to 10%-chromium steels. Leveraging this insight, Saarschmiede has produced full-size trial rotors to develop and refine production procedures, with these prototype components currently undergoing extensive testing to validate their performance and potential for advanced high-temperature applications.

Approximately 75% of the worldwide energy supply is based on fossil energy but the discussions on CO 2 emission require improvements of the conventional power technologies and also an increase of renewable energy resources. Over the past 40 years, enormous efforts, especially in the development of new materials, were made to establish the technology for the ultra-supercritical power plants, which are the standard of today’s power generation. For decades voestalpine Boehler Special Steel has been a full package supplier of customized high quality special steels and forgings with close relationships to plant manufacturers to provide products ahead of their time. This paper reports on improvements and research activities of the currently best available martensitic 9% Cr steel FB2 and the latest generation, the so-called MarBN steels, raising the operating temperatures of the 9% Cr steel class from 620 °C to 650 °C. Increasing the operating temperature requires adaptations in processes and manufacturing methods to adjust optimized microstructures with improved toughness properties and increased creep rupture strength at the same time. The microstructure of two Boron containing 9% Cr steels, FB2-2 and NPM1, developed within the framework of COST / KMM-VIN, have been investigated comparatively after different heat treatments and discussed after creep rupture tests at 650°C. The results show a dependency of the creep rupture strength on the stability of precipitates and the creep rupture time of both steels was increased by more than 30 % without negatively affecting the creep rupture strain and impact values.

This work describes the repair procedure conducted on the High Pressure/Intermediate Pressure (HP/IP) and generator rotors of a 180 MW steam turbine General Electric (GE) - STAG207FA type D11 installed at La Sierra Thermoelectric Power Plant in Puerto Nare, Colombia. A lubricant supply failure at base load caused severe adhesive damage to the shafts in the bearing support areas and a permanent 3.5 mm bow at the HP/IP rotor mid span section, which required a complex intervention. The repair process began with the identification of the rotors manufacturing material through in-situ metallographic replicas, handheld XRF analysis and surface hardness measurements. Volumetric manual Gas Tungsten Arc Welding (GTAW) welding reconstruction of cracked areas followed by a surface overlay using GTAW and Plasma Arc Welding (PAW) welding processes were applied with a modular mechanized system, where a stress relief treatment through vibration was implemented with the help of computational simulations carried out to determine the fundamental frequencies of the rotors. Geometric correction of the HP/IP rotor mid span section was achieved thanks to the excitation of the rotor at some fundamental frequencies defined by the dynamic modeling and the use of heat treatment blankets at specific locations as well. Finally, after machining and polishing procedures, the power unit resumed operation eleven months after the failure and remains in service to the present date.

The spalling of oxide scales at the steam side of superheater and reheater of ultra-supercritical unit is increasingly serious, which threatens the safe and economic operation of the boiler. However, no effective monitoring method is proposed to provide an on-line real-time detection on the spalling of oxide scales. This paper proposes an on-line magnetic non-destructive testing method for oxide granules. The oxide scale-vapor sample from the main steam pipeline forms liquid-solid two-phase flow after the temperature and pressure reduction, and the oxide granules are separated by a separator and piled in the austenitic pipe. According to the difference of the magnetic features of the oxide scales and the austenitic pipe, the oxide granule accumulation height can be detected through the spatial gradient variations of the magnetic induction. The laboratory test results show that the oxide scale accumulation can be accurately calculated according to the spatial gradient changes around the magnetized oxide granules, with the detection error not exceeding 2%.

Sufficient available energy in combination with lowest environmental pollution is a basic necessity for a high standard of living in every country. In order to guarantee power supply for future generations it is necessary to use fossil fuels as efficient as possible. This fact calls for the need of power plants with improved technologies to achieve higher efficiency combined with reduced environmental impact. In order to realize this goal it is not only a challenge for power station manufacturers, but also for manufacturers of special steels and forgings, who have to produce improved components with more advanced materials and more complex manufacturing processes. This paper reports about experiences in the fabrication of forged components for gas and steam turbines followed by achievable mechanical properties and ultrasonic detectability results. The materials are the creep resistant martensitic Cr steels developed in the frame of the European Cost research programme. Whereas Boron containing 10% Cr steels are suitable for steam temperatures of 625°C and slightly higher, Ni-based alloys shall be used for temperatures of 700°C and above. One pilot rotor forging, representing a HP-rotor for welded construction, has been manufactured out of alloy Inconel 625 within the frame of the European Thermie project AD700.

A failure of the upper casing of the circulation pump led to a big damage in the PP Staudinger unit 5 on 12th of May 2014. According to the §18(2) BetrSichV an extensive root cause analysis (RCA) was started. From the beginning on different lines of activities were initiated to handle the situation with the required diligence. Decisions were made, taking into account safety regulations, possibility of repair and best practice engineering. Following the board decision to repair the unit 5, a lot of detailed work was done. All of the performed work packages were linked in different timelines and needed to meet in the key points. Consequently it was a challenge to achieve the agreed date of unit 5 restart on 15th of January 2015. The unit restart on the targeted date was a proof of the excellent collaboration between all involved parties. The presentation gives a summarizing overview about the damage, the main results of the RCA and the repair activities.

Critical sections of steam plants and heat-recovery steam generators require materials with enhanced properties such as 9Cr-1Mo steel. Ensuring compliance with specifications for heat treatment, chemical composition, contamination limits, and joint design is crucial to prevent premature failures. This study describes the development of a user-friendly, multi-property nondestructive sensor arrangement to qualify heat-treated 9Cr-1Mo steel. Experimental results demonstrate that correlations between thermal heat treatment and electronic, magnetic, and elastic measurements can determine if T91 steel achieves the necessary microstructure and properties for service. Additionally, rejected parts can be assessed for microstructural issues causing unacceptable properties. The techniques utilize a common electronic setup with different sensors, requiring calibration for specific NDE systems and sensor setups, high-speed data acquisition, and frequency analysis (FFT). Further development on crept and welded samples is recommended to enhance NDE practices for in-service T91 steel conditions.

To solve crack problems at the tube elbow induced by high depth-to-width ratio longitudinal defects on the inner wall of boiler tube, a number of testing experiments and testing methods have been applied to analysis on the sensitivity and correspondence of such defects, and it has been found that the flattening test has an outstanding advantage to detect such defects. However, according to relevant standards, the judgment is controversy. It can be noted from the research that if a steel tube with a ratio of wall thickness to outer diameter larger than 0.1 is turned prior to the flattening test, to reduce such ratio to be less than or equal to 0.1, the shortcomings in detection and evaluation of such defects specified in the current relevant standards of many countries can be effectively overcome. The method has been proposed and adopted preliminarily in the relevant Chinese standard.

In order to meet the 2010-2020 DOE Fossil Energy goals for Advanced Power Systems, future oxy-fuel and hydrogen-fired turbines will need to be operated at higher temperatures for extended periods of time, in environments that contain substantially higher moisture concentrations in comparison to current commercial natural gas-fired turbines. Development of modified or advanced material systems, combined with aerothermal concepts are currently being addressed in order to achieve successful operation of these land-based engines. To support the advanced turbine technology development, the National Energy Technology Laboratory (NETL) has initiated a research program effort in collaboration with the University of Pittsburgh (UPitt), and West Virginia University (WVU), working in conjunction with commercial material and coating suppliers as Howmet International and Coatings for Industry (CFI), and test facilities as Westinghouse Plasma Corporation (WPC) and Praxair, to develop advanced material and aerothermal technologies for use in future oxy-fuel and hydrogen-fired turbine applications. Our program efforts and recent results are presented.

The toughness of girth welds in 9Cr-1Mo-V and 9Cr-0.5Mo-V steel seamless pipe (ASME SA-335 Grades P91 and P92, respectively) made using the flux-cored arc welding (FCAW) process was evaluated. Electrodes from two different suppliers were used for production quality welding of each steel. The welds received post-weld heat-treatment (PWHT) in accordance with the requirements of the ASME Code. The objective of the work was to determine if the fracture toughness of the FCAW welds was acceptable for high-temperature steam piping. Toughness was measured using standard sized Charpy V-notch impact specimens. The specimens were oriented transverse to the weld seam with notch located approximately in the center of the weld metal and parallel to the direction of weld seam. Full-range (lower to upper shelf) Charpy impact energy and shear area curves were developed for each weld joint. These were used to estimate the temperatures corresponding to 30 ft-lb average impact energy. The estimated temperatures were well below the service temperature but were above the typical hydrostatic test temperature.

Martensitic steel P91 with higher creep strength was first introduced as thick section components in power plants some 18 years ago. However, more recently a number of failures have been experienced in both thick and thin section components and this has given rise to re-appraisal of this steel. Thick section components are generally known to have failed due to Type IV cracking. Furthermore, due to the restructuring of the electricity industry worldwide many of the existing steam plant are now required to operate in cycling mode and this requires the use of materials with high resistance to thermal fatigue . Here high strength P91 is assumed to offer an additional benefit in that the reduced section thickness increases pipework flexibility and reduces the level of through wall temperature gradients in thick section components. Because of this envisaged benefit a number of operators/owners of the existing plant, especially in the UK, have been substituting these new higher strength steels for the older materials, especially when a plant is moved from base load to cyclic operation. There has also been a perceived advantage of higher steam side oxidation resistance of superheater tubes made from high Cr steels. For the Heat Recovery Steam Generators (HRSGs) used in Combined Cycle Gas Turbines (CCGTs) there is a requirement to produce compact size units and thus high strength steels are used to make smaller size components. This paper discusses these issues and compares the envisaged benefits with the actual plant experience and more recent R&D findings. In view of these incidents of cracking and failures it is important to develop life assessment tools for components made from P91 steel. ETD has been working on this through a ‘multi-client project' and this aspect will be discussed in this paper.

A 10%Cr martensitic steel for rotor applications, COST FB2, was used in 620°C steam turbines for about four years in China. In order to increase the unit efficiency to 50% of the coal-fired power plant, an advanced 630°C steam turbine developed by DongFang Turbine Co., Ltd will be put into operation in 2021. A three-ton middle-scale prototype turbine rotor forging (3387FC1) was developed and evaluated through the collaborative work of DongFang Turbine and the Japan Steel Works (JSW) using JMATR, a high-performance heat-resistant steel developed by JSW. Test results for the prototype rotor, including homogeneity of chemical composition, ultrasonic tests, mechanical properties, and long-term creep behaviors, and microstructure, are presented and discussed.

A research program has been initiated to develop the first predictive methodology for corrosion fatigue life in steam turbine blades, addressing a critical gap in current understanding despite extensive research into corrosion pitting and fatigue failure. The study focuses initially on dual-certified 403/410 12% Cr stainless steel, utilizing a newly developed test facility capable of conducting high-cycle fatigue tests in simulated steam environments at 90°C with controlled corrosive conditions. This testing platform enables the investigation of various steady and cyclic stress conditions, establishing a foundation for future testing of other blade steels and the development of comprehensive blade life estimation techniques.