Structural Health Monitoring for Conventional Power Plants: Solutions for Operational Challenges

2017 ◽  
Author(s):  
Jürgen Rudolph ◽  
Steffen Bergholz
Keyword(s):  
Power Plants ◽  
Low Cycle Fatigue ◽  
Thermal Power ◽  
Assessment Method ◽  
Detailed Knowledge ◽  
Thermal Power Plants ◽  
Design Codes ◽  
Highly Qualified ◽  
Structural Health ◽  
Creep Fatigue

The load follow operation of thermal power plants in the context of the German “Energiewende” is a big challenge for those power plants. In this context TMF/SHM methods gain increasingly in importance. Most existing power plants do not actually work any more according to the load profile which was originally specified. Load monitoring with the potential of optimization of operational modes combined with highly qualified fatigue and creep-fatigue assessment modules is a central concern. A lot of new methods were developed for getting appropriate information about the structural health situation of loaded components and prevent premature damage. In this context, it is essential to process both design load data as well as information of the real operational load situation and combine this with a highly qualified assessment method based on the relevant design codes for conventional power plant components such as EN 12952-3 and EN 13445-3. In the case of thermal power plants both fatigue due to cyclic loading and creep due to high temperatures (and their combination) play an important role. Note that there is a change of dominating damage mechanisms and dominating damage locations (from creep towards low cycle fatigue) due to new (load follow) operating modes. This implies the qualified assessment of fatigue damage respectively combined creep-fatigue phenomena. Due to the detailed knowledge of stress histories, temperatures and the duration of hold times a best forecast can be given. A staged concept is envisaged consisting of a simplified estimation according to conventional design codes (EN 12952-3 / EN 13445-3) and a detailed solution based on the application of a non-linear material model.

Grain Boundary Cracking of Nickel-Based Alloy 625 Under Creep Loadings at Elevated Temperatures

2019 ◽  
Author(s):  
Yan Liang ◽  
Yifan Luo ◽  
Ken Suzuki ◽  
Hideo Miura
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Power Plants ◽  
Elevated Temperatures ◽  
Thermal Power ◽  
Thermal Power Plants ◽  
Alloy 625 ◽  
Creep Fatigue ◽  
Creep Loading ◽  
Initial Cracks

Abstract Since the operating condition of thermal power plants has become harsher for minimizing the emission of CO2, Ni-based superalloys, such as Alloy 617 and 625, have been used in the plants to replace the conventional ferritic materials. Unfortunately, the increase of coefficient of thermal expansion compared with conventional steels is a concern. In addition, Ni-based superalloys have to suffer creep-fatigue random loading because thermal power plants have to compensate the random output of various renewable energies. It was found that the lifetime of Ni-based superalloys under creep-fatigue loading was much shorter than that under simple fatigue or creep loading. Thus, it has become very important to clarify the crack mechanism and establish the quantitative theory for estimating their lifetime under various loading conditions at elevated temperatures. Thus, the elucidation of the initial damage mechanism of Alloy 625 under various loading is indispensable. Hence, the initial cracking mechanism of Alloy 625 at grain boundaries under creep loading was investigated experimentally. The creep test was applied to small specimens in Argon atmosphere. The change of the micro texture during the creep test was observed by using SEM. It was confirmed that all the initial cracks appeared at certain grain boundaries. The change of the crystallinity was observed by EBSD (Electron Back-Scatter Diffraction) analysis quantitatively. It was found that the local accumulation of dislocations at the cracked grain boundaries caused the initial cracks at those grain boundaries. The initiation of cracks appeared clearly between two grains which had difference of KAM (Kernel Average Misorientation) values larger than 0.2. Therefore, dislocations were accumulated at one side of the grain boundary. By measuring the KAM values near grain boundaries, the appearance of initial cracks can be predicted approximately.

Findings on Creep-Fatigue Damage in Pressure Parts of Long-Term Service-Exposed Thermal Power Plants

1985 ◽  
Vol 107 (3) ◽  
pp. 260-270 ◽  
Author(s):  
F. Masuyama ◽  
K. Setoguchi ◽  
H. Haneda ◽  
F. Nanjo
Keyword(s):  
Fatigue Damage ◽  
Power Plants ◽  
Thermal Power ◽  
Field Experiences ◽  
Creep Damage ◽  
Thermal Power Plants ◽  
Damage Analysis ◽  
Creep Fatigue ◽  
Fatigue Damage Analysis

The increase of long-term service exposure to thermal power plants, the tendency toward intermediate and cyclic operation to meet the change in electric power demand and supply situation, and the requirement to develop higher-temperature and higher-pressure plants have led to increasing attention towards the reliability improvement. This paper presents findings from field experiences of cracking or failure and two types of damage analyses—(1) creep-fatigue damage analysis based on the life fraction rule and (2) metallurgical damage analysis—of boiler pressure parts that have been exposed to long-term elevated temperature service. The field experiences are (1) cracking or failure of thick-walled Type 316 stainless steel pressure parts in the main steam line of an ultra-supercritical thermal power plant and (2) dissimilar metal weld joints for boiler tubing. The creep-fatigue damage analysis of these pressure parts showed a reasonable correspondence with the field experience. According to the creep-fatigue damage analysis and the metallurgical damage analysis, most of damage was restrained creep mode phenomenon without deformation. The creep damage was composed of metallurgical damage and mechanical damage such as microvoids and structural defects. One method of simulating field experienced creep damage was proposed and performed. As a result, the process of creep voids being generated and growing into cracks without deformation was successfully observed. Also a review of the current status of nondestructive detecting methods of creep damage suggests that detecting the creep voids metallurgically is more practical at the present time than doing so analyzing the changes in physical properties of the material. It is also suggested that, in the metallurgical approach, detecting the creep voids and cracks by replica method and anlayzing precipitates for evaluation of material deterioration by precipitate extraction method will make it possible to successfully address the problem of plant equipment creep damage evaluation and life prediction.

scholarly journals Structural-&-Phase Condition and the Damageability of the Welded Joints of Steam Pipelines at Thermal Power Plants

2021 ◽  
pp. 56-63
Author(s):  
Vitaly Dmitrik ◽  
Igor Kasyanenko ◽  
Alexandr Krakhmalyov
Keyword(s):  
Service Life ◽  
Welded Joints ◽  
Power Plants ◽  
Low Cycle Fatigue ◽  
Thermal Power ◽  
Economic Effect ◽  
Structural Phase ◽  
Initial Structure ◽  
Thermal Power Plants ◽  
Phase Condition

The authors studied the interrelation between the type of structure and the damage rate of the welded joints of steam pipelines made of the heat-resistant pearlitic steels that were operated for a long time, i.e. more than 270 thousand hours in the conditions of creepage and low-cycle fatigue. The purpose of this research was to establish the interrelation between the structural-&-phase condition of the metal used for welded joints of the elements of steam systems and their damageability rate for the service life of welded joints exceeding 270 thousand hours. During the studies, the methods of optical and electron microscopy were used according to the requirements of the guideline documentation and also the methods that are used for the determination of mechanical properties. The level of their reliability has been substantiated and the residual life has been determined. To impart functional performances to welded joints we used well-known methods that were appropriately emended according to the structural changes of above joints. Such changes condition the conversion of the original structure of welded joints into the ferrite-carbide mixture. The availability of the conversion process of the initial structure on the thermal action zone sections (TAZ) of welded joints has essential distinctions due to a different disposition of metal to its own damageability. On the whole, the welded joints are damaged more intensively in comparison to the basic metal of steam pipelines. The analysis of the structural state of welded joints in the steam pipelines of thermal power plants as for the extension of their service life results in a considerable economic effect. Understanding the fact that the metal deterioration in welded joints adheres mainly to the fragile mechanism we managed to establish the level of their damageability that demands the renewal of damaged welded joints. We believe that the damageability level of welded joints that tots up to 0.25 or 0.35 of the volume of their TAZ section should be considered as critical for the service life exceeding 270 thousand hours. The damaged welded joints should be renewed throughout the time period of 15 to 20 thousand hours as soon as the specified damageability level is attained.

Microscopic Analysis of the Initiation of High-Temperature Damage of Ni-Based Heat-Resistant Alloy

2016 ◽  
Author(s):  
Takuya Murakoshi ◽  
Ken Suzuki ◽  
Isamu Nonaka ◽  
Hideo Miura
Keyword(s):  
Co2 Emissions ◽  
Power Plants ◽  
High Efficiency ◽  
Coefficient Of Thermal Expansion ◽  
Thermal Power ◽  
Fatigue Loading ◽  
Thermal Power Plants ◽  
Loading Conditions ◽  
Creep Fatigue ◽  
The Difference

It is imperative to reduce greenhouse-effect gas such as CO2. Since the emission of CO2 from fossil fuel combustion to generate electricity is a critical quantity, accounting for 42% of global CO2 emissions in 2013 [1], high efficiency of thermal power plants is indispensable for reducing the CO2 emissions. In order to further improve thermal efficiency of thermal power plants, various R&D projects have been conducted (such as Thermie 700 in the EU and DOE-Vision 21 in the US) to develop A-USC (advanced ultra-supercritical) power plants of the 700°C-class. Alloy 617 is a candidate alloy for boiler tubes and pipes. Since it has higher coefficient of thermal expansion than conventional ferritic steels, however, the increase in the thermal stress is of concern in the power plant components. In addition, it is important to consider the effect of creep-fatigue loading on the lifetime of the components in the design and maintenance of the components. This is because frequent output change is inevitable for assuring the stable and reliable supply of electricity under the combination with renewable energies. Conventionally, the creep-fatigue damage has been evaluated by linear cumulative damage rule. However, it has been found that there are a lot of loading conditions and materials to which the rule can’t be applied [2–3]. Therefore, it is indispensable to establish the method for evaluating the total damage of materials under creep-fatigue loading conditions. Thus, the authors conducted fatigue and creep-fatigue tests and observed the change of the micro texture to elucidate the damage evolution of the alloy from the viewpoint of the change of the order of atom arrangement using EBSD (Electron Back-Scatter Diffraction) analysis. As a result, it was found that the difference of damage accumulation under fatigue and creep-fatigue loadings appeared in the change of the GROD (Grain Reference Orientation Deviation) value in the inelastic strain range. Therefore, the difference in the damage mode between fatigue and creep loads can be analyzed by using these KAM and GROD values.

On the prospect of introduction of plasma ignition in power boilers

2019 ◽  
Vol 12 (1) ◽  
pp. 22-28
Author(s):  
V. Ye. Mikhailov ◽  
S. P. Kolpakov ◽  
L. A. Khomenok ◽  
N. S. Shestakov
Keyword(s):  
Russian Federation ◽  
Solid Fuel ◽  
Power Plants ◽  
Thermal Power ◽  
Fuel Oil ◽  
Solid Fuels ◽  
Thermal Power Plants ◽  
Plasma Ignition ◽  
The Russian Federation ◽  
Capital Construction

One of the most important issues for modern domestic power industry is the creation and further widespread introduction of solid propellant energy units for super-critical steam parameters with high efficiency (43–46%) and improved environmental parameters. This will significantly reduce the use of natural gas.At the same time, one of the major drawbacks of the operation of pulverized coal power units is the need to use a significant amount of fuel oil during start-up and shutdown of boilers to stabilize the burning of the coal torch in the variable boiler operating modes.In this regard, solid fuel TPPs need to be provided with fuel oil facilities, with all the associated problems to ensure the performance (heating of fuel oil in winter), reliability and safety. All of the above problems increase both the TPP capital construction costs, and the electricity generating cost.A practical solution to the above problems at present is the use of a plasma technology for coal torch ignition based on thermochemical preparation of fuel for combustion. The materials of the developments of JSC “NPO CKTI” on application of plasmatrons in boilers of thermal power plants at metallurgical complexes of the Russian Federation are also considered.Plasma ignition systems for solid fuels in boilers were developed by Russian specialists and were introduced at a number of coal-fi red power plants in the Russian Federation, Mongolia, North Korea, and Kazakhstan. Plasma ignition of solid fuels is widely used in China for almost 30% of power boilers.The introduction of plasma-energy technologies will improve the energy efficiency of domestic solid-fuel thermal power plants and can be widely implemented in the modernization of boilers.During the construction of new TPPs, the construction of fuel oil facilities can be abandoned altogether, which will reduce the capital costs of the construction of thermal power plants, reduce the construction footprint, and increase the TPP safety.

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