Operation flexibility and the high efficiency of thermal cycle are the two hot research topics for the steam turbine unit. For the operation flexibility, it requires the turbine unit be able to start up quickly and frequently, and good thermal fatigue properties of the components are a must. On the other hand, the trend to higher temperature with ultra supercritical (USC) steam is the key drive of ongoing development for the validation of a method to improve the thermal cycle efficiency, but the application of the higher steam temperature will intensify the component’s thermal fatigue. In this paper, a high pressure inner casing for the new designed solar steam turbine was studied, and the Finite Element Method (FEM) combined with linear elastic material was applied to simulate the transient stress and temperature fields during the daily warm/hot startup process. On the basis of the stress spectrum in the critical zone, the standard DIN EN-12952-3 and the fatigue curve were used to evaluate the low cycle fatigue life consumption in the transient process.

Ancillary exhaust system structural design for turbines typically employs a separation of responsibilities between the design and installation functions. The design expectations must be implemented correctly during the installation phase to allow long-term serviceability and success of the turbine exhaust system. This paper will explore a case study reviewing bolt tightening of duct structural angle and plate flange joints using compressible high temperature fiberglass gasket material, as well as design suggestions for metal-on-metal duct sliding support joints to structural steel. Improper design and operation can lead to failure, downtime, warranty cost and reduced design life of the exhaust system. It is not uncommon for field installation personnel to modify key system design requirements during the installation phase; typically out of habit, perceived best practice, missed installation instructions and/or misunderstanding the system behavior. In addition, maintenance recommendations are often overlooked. Literature provides extensive background for bolting of stationary metal-to-metal plate joints, rigid gaskets and pressure vessel joints. There is a gap with respect to structural angle and plate flange joint bolt tensioning using compressible fiberglass gaskets at low pressures and high temperatures. Much of the industry standard tightening philosophy is useful, but has not been extensively studied and written about with respect to flanges under high exhaust temperatures or for sliding joints exposed to thermal expansion. This paper summarizes current industry practice, presents relevant test data and a case study, analyzes the effects of high thermal stresses, and recommends a tightening procedure for typical field applications of flange joints using high temperature gaskets, and the design of metal-to-metal sliding support joints.

Combustion turbines are frequently used because they provide the most power in the smallest footprint and their modular design makes them an economical choice. These machines are used across all land-based industries as well as marine applications. The exhaust system must perform its basic function of conducting exhaust gases, which can be as high as 1250° F (675° C), safely away from the adjacent equipment and workers, and mitigate the exhaust noise under a wide range of requirements and conditions. In addition, new requirements limit shell temperatures and exhaust leakage to prevent fire or explosion of fuel gas that may leak from equipment (ATEX). This paper presents a review of the analytical processes used in the development of a silencer system to achieve optimal performance metrics. These systems are typically comprised of parallel baffles for a wide range of conditions including aero-acoustical performance, system pressure and high flow rates, thermal stresses, environmental conditions (ocean, seismic and wind), flow-induced vibration, corrosion, and fatigue – design life analysis. The specific requirements of the baffle design will be discussed through a specific case study relative to typical rectilinear (parallel) baffles used in many installations, including land-based power generation plants (Figure 1), and offshore platforms (Figure 2). This paper will discuss the analytical methods used to address these challenges via a case study. A combination of static, vibration-pulsation and dynamic structural analysis with specific attention to the seismic analysis of the parallel baffles used in skirt and structural steel supported vessels, as well as acoustical design and flow modeling techniques are used to evaluate the design options.

The study presented here designed a steam film cooling system for the thick-wall cylinder components used in the 700°C steam E turbine power plant, and investigated temperature, thermal stress, and creep behavior of the thick-wall cylinder with the cooling hole structure. Analysis of film cooling behavior with a single cooling hole at different blowing ratios is numerically conducted to determine the design of a steam cooling system with multiple cooling holes. Boththe temperature and stress analysis of the thick-wall cylinder with either a single cooling hole or multiple cooling holes are performed for comparison. The British R5 guidance procedure is applied to assess the creep damage of the component after 200,000 h operation. Maximum creep damage d c is approximately 0.0008 at the leading edge of the cooling hole in Row 1.

W-added 12% Cr ferritic heat resistant steel has been used as a steam turbine rotor material. The turbine rotor material is damaged by high temperature creep and fatigue due to starts and stops and changing load of power generation, which results in crack initiation and growth. In the studies done before, the law of crack growth life under creep-fatigue conditions was characterized and clarified that the characteristics of crack growth life of various load frequencies under different temperatures change from fatigue to creep behavior through an inflection region. The law of crack growth life under creep-fatigue interactive conditions has been reported and evaluated by monotonous linear law. On the other hand, it has been indicated that the characteristics of crack growth life under creep-fatigue condition can be represented mathematically by a three dimensional characteristic curved surface based on non-equilibrium science. In this study, crack growth tests using standardized C(T) specimens of W-added 12% Cr ferritic heat resistant steel were conducted under various conditions of stress holding time, applied stress and temperature. To evaluate the effect of cycle dependent and time dependent mechanisms on crack growth life, a method of separate estimation of cycle dependent mechanism from the time dependent mechanism based on the concept of three dimensional characteristic curved surface based on non-equilibrium science were used. As a result, the effect of load frequency on crack growth life was characterized and the predictive law of crack growth life for W-added 12% Cr ferritic heat resistant steel under creep-fatigue interactive conditions based on the concept of Q * with the transition function of crack growth life was estimated.

Reciprocating engines and turbines continue to provide fuel efficient, clean and flexible motive power for many gas compression and power generation applications. Compression and/or power generation stations that were originally built in isolated areas are now in or near neighborhoods, requiring greater focus on acoustic performance. New emission regulations now require catalyst systems on most all gas engines. These new requirements have increased the complexity for a modern reciprocating engine exhaust system including both new installations and retrofit. While these engines are durable and flexible, they create many challenges for the exhaust system designer. The exhaust vessels are commonly installed on top of structural steel supports, self-supported directly on the foundation or skid via a shell skirt, (Figure 1). This paper will discuss the analytical methods used to address these challenges. A combination of static, vibration-pulsation and dynamic structural analysis with specific attention to the seismic analysis of the skirt supported vessels, as well as acoustical design and flow modeling techniques are used to evaluate the design options. The overall objective of the system design will be discussed relative to the typical free standing vertical vessel/stack systems used at many compression and power generation stations.

Steam line blowing is an operational cleaning method used to clean steam piping and reheaters prior to turbine powering for steam power plants. This paper focusses on the application and challenges associated with the steam blowing of large solar thermal collection power plants. The boiler configuration, located atop an over 400 foot tall tower, in a large solar thermal collection plant poses some challenges not associated with other steam supply methods. As a result of the flow path configurations and steam mass required for blowing the cold reheat, reheater, and hot reheat portions of the plant, attemperation is required to control temperatures in the reheater. The use of multiple flow paths and stages through the reheater also requires some additional consideration. Where in a fossil powered plant the losses through the reheater are based on the inlet vs. outlet conditions, additional vendor data is required to model the internal sections of the reheater in greater detail. Methodologies developed for fossil powered plants can be applied to large solar thermal collectors with special consideration for the unique configurations and constantly changing solar conditions associated with the plants. The smaller margins associated with these plants requires more rigorous modeling of the system components.

Following the in-service failure of a pipe clamp on one of two combustion turbines (CT-2, for reference) at a natural gas fired combined cycle unit, station personnel found three other pipe clamps in CT-1 that were similarly damaged. One of the cracked pipe clamps from CT-1 was submitted to the metals laboratory for analysis to determine the cause of the failure. Subsequently, a piping segment and one additional clamp from CT-2 was submitted to the lab for analysis of the external deposit and were found to contain similar cracks in the clamp. The clamps are used to secure the steam piping to the outlet portion of the transition pieces within the CT. Analysis of the cracks identified them as intergranular, initiating on the ID surface of the clamp (where the applied stresses of the clamp are in tension) but which would be external to the pipe itself. Analysis of the actual deposits showed them to be very high in sulfur (soluble anion analysis identified them as sulfates) and minor amounts of fluorides, with no detectable chlorides either by SEM/EDS or by soluble anion analysis. The area is washed down during shut-down and an analysis of the washwater additive showed very low levels of chloride (7ppm) and sulfate (4 ppm). Concentration of chlorides could be occurring as the units heat up, but none could be identified on the actual fracture surface or the deposit with any certainty. The cracking is consistent with intergranular stress-corrosion cracking, although a specific causative agent/environment could not be identified with any certainty. Given the operating temperatures, any SCC that would be occurring would likely be during shut-down or start-up in order for an aqueous environment to be present. The final disposition of these clamps is for regular replacement during the routine overhauls.

This paper provides a part of series of “Development of an Evaluation Method for Seismic Isolation Systems of Nuclear Power Facilities” [1]–[4]. This part describes the work schedule of this project and the summary of a seismic design for crossover piping system. Since the Southern Hyogo Prefecture Earthquake in 1995, a seismic isolated design has been widely adopted for Japanese typical buildings. The Japanese government accepted utilizing seismic isolation technology for nuclear power facilities with the 2006 revision of the “Regulatory Guide for Reviewing Seismic Design of Nuclear Power Reactor Facilities”. Under these backgrounds, the Japan national project with the participation of all electric power companies and reactor vendors has been started from 2008 to develop seismic isolation systems of nuclear power facilities under the support of the Ministry of Economy, Trade and Industry. In the design of seismic isolated plant, the crossover piping systems, such as Main Steam line and other lines related to the safety system have the important roles for overall plant safety. Therefore, the design of multiply supported piping systems between isolated and non-isolated buildings is one of the major key issues. This paper focuses on the seismic response analysis of Main Steam crossover piping between seismic isolated Reactor Building and non-isolated Turbine Building. Multiple input response spectra and time history analyses of the crossover piping have been performed and the structural integrity of piping and the validity of the multiple input analysis method have been verified based on comparisons with the results obtained by conventional response spectrum analysis using enveloped floor response spectrum.

When applied with physically meaningful inputs that have been guided by analytical analysis, numerical modeling is a quick and cost-effective virtual experiment that has the added benefit of being free of experimental error. Furthermore, with the rapidly evolving processing power of modern computers, highly complex structures and physical phenomena can be modeled with relative ease. This paper discusses the application of semi-analytical and fully numerical modeling methods as employed for the study of ultrasonic techniques in complex structures and materials. A brief review of these two numerical modeling approaches is presented followed by several practical examples that highlight the utility of each technique. One example presented includes the simulation of the ultrasonic field created in a dissimilar metal weld by a linear phased array transducer. A second example presented includes the three-dimensional modeling of guided wave propagation through elbow fittings in a pipe. Finally, a metrological process for the translation of real, geometrically complex components into the modeling environment is presented and the modeled response from fatigue cracking in a thick walled carbon steel turbine shell is compared with the actual defect response.

A numerical analysis of the thermal stratification in the upper plenum of the MONJU fast breeder reactor was performed. Calculations were performed for a 1/6 simplified model of the MONJU reactor using the commercial code, CFX-13. To better resolve the geometrically complex upper core structure of the MONJU reactor, the porous media approach was adopted for the simulation. First, a steady state solution was obtained, and the transient solutions were then obtained for the turbine trip test conducted in December 1995. The time dependent inlet conditions for the mass flow rate and temperature were provided by JAEA. Good agreement with the experimental data was observed for the steady state solution. The numerical solution of the transient analysis shows the formation of thermal stratification within the upper plenum of the reactor vessel during the turbine trip test. The temporal variations of temperature were predicted accurately by the present method in the initial rapid coastdown period (∼300 seconds). However, the transient numerical solutions show a faster thermal mixing than that observed in the experiment after the initial coastdown period. A near homogenization of the temperature field in the upper plenum is predicted after about 900 seconds, which is a much shorter-term thermal stratification than the experimental data indicates.

The steam supply piping connected to the high pressure (HP) turbine of APR1400 (Korea’s advanced power plant 1400 MW-class) is a typical example of multi-supported piping system, and it is routed from the Containment building to the Turbine building via the Main Steam Isolation Valve House in the Auxiliary building. In the seismic analysis of this piping system, using the Enveloped Response Spectrum (ERS) method, a commonly used methodology for seismic analysis of nuclear power plant piping in industry circles, generates overly conservative analysis results. Therefore, Time History Method (THM) which applies excitation characteristic of each support attached to individual building was used to eliminate unnecessary conservatism. However, it was noticed that the Time History Method requires considerable amount of labor and time in generating combined time history equivalent to the spectrum applied for each support although it is regarded as the most exact and realistic method for seismic analysis. The nuclear industry has been making lots of efforts in finding out the mathematic logicality and practical applicability to resolve this issue. This paper deals with parametric research on combination effects of responses between support groups, damping effects, and modal combination method with close modes in applying the Independent Support Motion (ISM) method to the analysis model of the steam supply piping connected to the high pressure turbine of APR1400. Quantitative assessment and comparison with the analysis results of the ERS method and THM were also carried out. As a result, it is shown that the analysis results of the ISM method together with the SRSS combination between support groups, 4% damping with ±15% spectrum peak broadening and grouping of modal combination are remarkably similar to those of THM.

Multi-axial fatigue life assessment is important in power generation, aerospace, automotive, and many other industries. The newly developed path-dependent multi-axial cycle counting and fatigue life assessment method has been shown effective for some applications. For instance, when stress range is used as the only driving force for fatigue failure, the method correlates high cycle fatigue test data well. The method consists of two parts: (1) maximum-range (or maximum distance) based cycle counting method, so that the method can be applied to 2-D and 3-D stress or strain space, as compared to the conventional rainflow counting method, which is based on the peak-valley concept, therefore, can be applied only to uniaxial (1-D) loadings; and (2) a path-length based stress range is used as the fatigue damage parameter replacing the traditional concept of stress or strain range, which is the difference between the peak value and the valley value of a cycle. This method has been justified using the classical fracture mechanics in multidimensional stress space. In this paper, we apply the method to analyze two additional classes of multi-axial fatigue test data reported in the literature: (1) low-cycle strain based tests, which has an important implications in high-temperature applications, such as piping/vessels in power industry, turbine, and automotive exhaust systems; (2) a series of test data that require an introduction of two parameters in either fatigue crack growth model or S-N curve based approach. For the latter, an incremental crack growth model reported earlier by the authors is recast to incorporate one additional stress based parameter to account either mean stress or maximum principle stress effects in multi-axial fatigue damage process, dependent upon material characteristics under consideration. The results show that strain-based low-cycle multi-axial fatigue data can be effectively correlated in the form of a single S-N curve using a path-dependent effective strain range definition. Furthermore, a two parameter based interpretation of the crack propagation model is capable of capturing effects of the maximum principle and mean stresses on multi-axial fatigue damage process associated with some of the test data. Finally, the physical basis of the method in these extended applications is discussed.

In the boiling water reactor (BWR), closure of a turbine stop valve (TSV) on the main steam piping system, hereafter called main steam (MS) line, will reduce the steam flow velocity to zero in about 100 msec (0.1 Sec) and create a pressure disturbance that propagates backward through the MS line toward the reactor pressure vessel (RPV). When the compression wave reaches the RPV, it expands into a region at lower pressure, transmitting a compression wave at acoustic speed from the pipe geometry into a complex geometric region at reactor pressure, bounded by the steam dryer and RPV inner wall surfaces. The arriving compression wave expands on the dryer surface, creating a pressure force, while simultaneously steam in the steam line, compressed from the valve closure to a pressure higher than that in the reactor, flows backwards into the RPV, creating a jet impingement, or “backflow” force on the dryer. Simplified, conservative modeling is applied in this study to obtain reasonable bounding loads which allow for the dryer curvature and other complexities of the dryer-vessel geometry.

Recently, huge earthquakes occurred in the world, such as Great East Japan Earthquake in Japan or huge earthquake in New Zealand in 2011. In Niigata-ken Chuetsuoki earthquake in 2007, turbine blade collisions with the casing were found. Therefore, it is very important to clarify the seismic response behaviors of the high-speed rotational shaft like turbine shafts, because high-speed rotation will cause characteristic dynamic effects, such as gyro moment. In this study, seismic responses of a disk-shaft system are evaluated analytically. The disk-shaft system is treated as an elastic shaft with a rigid disk. In this analysis, gyroscopic effects of a rotating disk are also considered. Equations of motion are derived for the translational and rotational motions when the system is subjected to both horizontal and vertical seismic excitations. Response behaviors of a rotating disk-shaft system are evaluated for sinusoidal excitations and seismic wave excitations. In the sinusoidal excitations, excitation frequencies and rotational speed are varied, and in the seismic wave excitations, seismic responses are evaluated for the waves with various predominant frequencies.

High energy pipes, carrying steam at high pressure and temperature, are very common in the industry. In this paper, a Fitness-For-Service assessment was performed for a pipeline connecting the boiler of a paper mill to the cogeneration turbine and the process headers. A pressure of 6.4 MPa and a temperature of 475 °C were the operating conditions for 230000 hours of continued service, thus arising concern about metal loss due to erosion/corrosion and high temperature creep damage. Original pipeline design information was unknown, hence, an extensive NDE program was carried out to obtain the required data for the FFS analysis. Because of the elevated number of in-service hours, an API 579-1 Level 3 assessment was required and a FE shell model of the line was set up to evaluate plastic strain accumulation due to creep through a time-dependant inelastic analysis. The predicted critical components were then investigated experimentally taking metallographic replicas in situ and the actual damage was finally, qualitatively, compared with that calculated with the API 579-1 procedures, with good agreement. The results of the assessment led to an estimate of 70000 hours of residual life for the pipeline and could drive the planning for future NDE according to a RBI approach.

A-parameter, void area ratio and other methods about creep void are used to estimate creep damage resulting from creep voids. However, these methods are based on not three-dimensional but two-dimensional geometry, though creep voids are three-dimensional cavities. By combining the 3D-EBSD method with SEM images, we have observed the three-dimensional shape of creep voids and their geometrical relationship with grain boundaries at first. The method is applied to 1Cr-1Mo-0.25V turbine rotor steel subjected to a creep rupture test (580°C, 180MPa). Also, interrupted creep specimens are prepared to observe the progress of void growth. Forty sections with 0.5 μm interval and 100μm × 100μm area are measured by mechanical polishing in order to reconstruct the three-dimensional shapes. In the results, four types of creep void are observed. One is sphere type whose radius is approximately 1μm. It is observed in the specimen whose creep life fraction is 25%. In the specimens with 50% and 75% creep damage, prolate and oblate spheroid whose radius is approximately 2.5μm are observed. Finally, connected voids are located within ruptured specimen. As the creep damage is progressed, not only void growth but also void nucleation is observed. Especially, on prior austenite grain boundary which is three-dimensionally perpendicular to the stress direction, creep voids are nucleated and grow in a concentrated manner. However, such nucleated small voids do not affect the void volume fraction.

Many engineering components, such as power plant steam pipes, aero-engine turbine discs, etc, operate under severe loading/temperature conditions for the majority of their service life. As a result, cracks can initiate and subsequently propagate over time due to creep. Damage mechanics is a robust method for the prediction of behaviour of components subjected to high temperature creep conditions and in particular, the Liu and Murakami model has proven to be a useful tool for the prediction of creep crack growth under such conditions. Previous methods for obtaining the constant of multiaxiality required for the use of such models, i.e. α , have relied upon the steady load testing of specimens designed to give a specific multiaxial stress-state, such as notched bars, and the failure time obtained. A series of results from finite element ( FE ) analyses based on the same geometry and loading/temperature conditions as the experiment, each performed with a different α -value, are then interpolated in order to identify the α -value which results in the same failure time, t f , as that of the experimental test. However, the stress-state present within such a specimen geometry (and therefore the α -value obtained) does not reflect the multiaxial severity of the stress state ahead of a crack tip. Therefore, for the application of the Liu and Murakami model to crack tip (i.e., creep crack growth) conditions, it follows that the α -value should be obtained from a multiaxial stress-state of equal severity to that to which it is to be applied, i.e. a crack tip. Therefore compact tension ( CT ) specimen creep crack growth data has been used in order to obtain the α -value. The process for the α -value determination is similar to that discussed for the notched bar, except that the interpolation of the time to failure is replaced with an interpolation of the time to a given crack length, t a . The resulting FE predictions based on CT and thumbnail crack specimen geometries, for a 316 stainless steel, are shown to be accurate in comparison to experimental results.

In this paper, experience and results of the Pipe integrity design project applied to Unit 2 of Armenian NPP in Metsamor are presented. The feedwater and steam piping lines, which were covered by the Project, are located in the turbine hall on the elevation of +14.7 m, outside the containment. Piping was assessed from point of view of both pipe rupture postulation criteria defined in SRP 3.6.2 [2] and in BTP 3.4 [4] and seismic margin requirements [5] based on the international practice for the NPPs in operation. Concerning hydrodynamic calculations, possible causes of steam and water hammer were assessed. To lower the stresses in critical locations and to solve the effects of steam/feedwater/emergency feedwater pipe whip, some measures have been proposed — installations of whip restraints, hydraulic snubbers, etc. Detailed design files have been prepared for the proposed measures. Within this project, ISI program was conducted, with application to the most loaded locations. Proposal of the first stage of inspections was given, taking into account the possibility that the inspections will be performed within one outage.

During the past 15 years many works have been done on Ageing Management Program (AMP) of Safety classed components in EDF. The paper will describe all the different aspects concerning these programs, and in particular the EDF step by step procedure and the major results. To-day, EDF is starting the 3 rd ten-year shutdown of all these 3-loop plants (34 plants). During the associated Safety Review, a specific task is devoted to ageing effects and control of all the safety concerned components. A large list of components has been reviewed: mechanical, civil engineering, instrumentation and control, cables, non metallic components. Few non safety but important in term of availability components are considered, like turbine or some balance of plant components. A general review of results and difficulties for 40 and 60 years are presented in the paper. The second part is devoted to a short review of our procedure with IAEA guidelines. The third part will shortly describe the associated R&D program for metallic components and knowledge management associated to AMP. The major conclusions are clearly supporting the needs of international basic procedure and harmonization on the major topics.