The effect of the steam temperature fluctuations during steady state operation on the remnant life of the superheater header

Kwon, Oh Geon; Myers, Matthew R.; Karstensen, A. D.; Knowles, David

doi:10.1016/j.ijpvp.2006.02.012

Cited by 14 publications

(4 citation statements)

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“…about 400 MPa and 500 MPa, respectively, with peak tensile stresses of 275 MPa and 340 MPa, respectively. The prediction of a large tensile stress in the axial direction is consistent with the results in [5] pertaining to observed ligament cracking in steam headers. Figure 15 present the corresponding TMF hysteresis loops for the representative cycle, for the same four locations.…”

Section: Sub-model Thermomechanical Analysessupporting

confidence: 87%

“…In [4], thermo-mechanical modelling of P91steel in complex power plant geometries, including 2 effects of varying thermal and mechanical loads representative of plant start-up was carried out using an elastic-plastic material model (without strain-rate effects). In [5], [6], [7] the inservice life of 2 1 / 4 Cr-1Mo steel power plant components has been investigated, based on a linear elastic finite-element analysis, which is expected to underestimate the component lifetime. Lifetime assessment of header geometries under system loading was examined in [8], which highlighted the importance of modelling both the global geometry and local subsections of a header geometry.…”

Section: Introductionmentioning

confidence: 99%

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Development of life assessment procedures for power plant headers operated under flexible loading scenarios

Farragher

Scully²,

O’Dowd

et al. 2013

International Journal of Fatigue

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Publication InformationFarragher, TP, Scully, S, O Dowd, NP, Leen, SB (2013) 'Development of life assessment procedures for power plant headers operated under flexible loading scenarios'. International Journal Of Fatigue, 49 :50-61. PublisherElsevier ScienceDirect 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 Abstract A finite element methodology for thermomechanical fatigue analysis of a subcritical power plant outlet header under realistic loading conditions is presented. The methodology consists of (i) a transient heat transfer model, (ii) a sequential anisothermal cyclic viscoplastic model and (iii) a multiaxial, criticalplane implementation of the Ostergren fatigue indicator parameter. The methodology permits identification of the local thermomechanical stress-strain response at critical locations and prediction of fatigue life and cracking orientation for complex transient, anisothermal, cyclic elastic-plastic-creep material behaviour. Measured plant data, in the form of steam and pipe temperature transients and steam pressure data, are employed to identify heat transfer constants and validate the predicted thermal response, with particular attention given to plant start-up and attemperation effects. The predictions indicate out-of-phase temperature-strain response at the header inside surface and in-phase response on the outside surface. Cooling transients are predicted to control damage and crack initiation at the inner bore, whereas heating transients are predicted to have a more damaging effect at weld locations. A representative test cycle is presented, which is shown to capture the salient thermo-mechanical cyclic damage of the realistic cycle. The predicted results correlate well with industrial experience in terms of crack (initiation) orientation, location and life. IntroductionThere is a need to understand the performance of candidate power plant materials for higher temperatures and pressures. 9-12% Cr steels are an example of such candidate materials, owing to their excellent mechanical properties, and steels such as P91 and P92 are already being utilised in power generation plant [1]. There is an increasing trend towards shifting of energy supply from conventional fossil fuel power plant to sustainable energies, e.g. wind power. To allow for the variable nature of renewable energy supply, there is a requirement to operate existing plant, designed for 'base-load' operation, with relatively infrequent shutdown and start-up, in 'load-following' mode, characterised by increased frequency of shutdown and start-up. This issue has increased the importance of design and assessment of materials and components for high temperature, pressurised plant with respect to thermomechanical fatigue (TMF) and creep-fatigue failure.Current header design does not consider cyclic thermal stresses and load cycling that can lead to creep-f...

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Section: Sub-model Thermomechanical Analysessupporting

confidence: 87%

Section: Introductionmentioning

confidence: 99%

Development of life assessment procedures for power plant headers operated under flexible loading scenarios

Farragher

Scully²,

O’Dowd

et al. 2013

International Journal of Fatigue

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“…In fact, in-service plant data show that loads fluctuate continuously, even during stable operation states (Carney and Gilman, 2011), as shown in Figure 1. Such fluctuations significantly aggravate fatigue damage in components such as boiler headers, shell-nozzle junctions (Samal et al., 2009), and pipes (Kwon et al., 2006), while fluctuating loads also cause creep damage to accumulate at varying rates. To enable timely assessment of the damage state of these critical components, evaluation methods should promptly identify the loading spectrum and analyze the damage state.…”

Section: Introductionmentioning

confidence: 99%

An online monitoring method for creep-fatigue life consumption with real-time damage accumulation

Hong

Cai

Wang

et al. 2021

International Journal of Damage Mechanics

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Online damage evaluation based on monitored complex cyclic loadings has become an important technique for reliability assessment, especially in high-temperature environments where creep occurs in addition to fatigue. Accuracy and rapidity of calculation are basic requirements for online damage evaluation methods. However, current creep damage evaluation methods seldom consider the fluctuation in stress, which leads to inaccuracy in life-consumption estimates. In addition, traditional cycle-counting methods are not applicable to online use. In this study, an online creep-fatigue damage evaluation method is proposed that accounts for the creep behavior that occurs under fluctuating loads. The cycle-counting method is modified from a rainflow-counting algorithm; it broadens the counting of half-cycles and adopts a new equivalent temperature in the stress-strain response calculation. The proposed method is explained in detail and demonstrated with a case study. The application of this method to a high-temperature, high-pressure pipe demonstrates its online applicability and accuracy. A time-matching algorithm is developed to display the damage evolution in real time, thus revealing the link between the incremental damage and the current load conditions, and yielding an intuitive demonstration of a given component’s state of health.

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“…Thermal expansion is the essential factor to generate thermal stress/strain in materials and it is, therefore, important to develop heat resistant steels/alloys with reduced thermal expansion to minimize the thermal stress and thereby suppressing degradation of the materials due to thermal fatigue conditions. [1][2][3][4][5][6] Ferritic heat resistant steels are widely used for large components in conventional fossil fired steam turbine power plants such as main steam pipes and headers etc. because of their relatively low cost, high strength/toughness and low thermal expansion coefficient.…”

Section: Introductionmentioning

confidence: 99%

Reduction of Thermal Expansion of Ferritic/martensitic Heat Resistant Steels -Alloying Effects on Thermal Expansion of <i>α</i>-Fe Phase-

Kobayashi

Fukunishi

2020

ISIJ Int.

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Alloying effects on the thermal expansion of the α-Fe phase in connection with the magnetic states were investigated with a final goal to design ferritic/martensitic heat resistant steels with a reduced thermal expansion coefficient at high temperatures. The thermal expansion coefficient decreases with increasing the content of the alloying elements M (M = Co, Cr and V) regardless of the types of the elements in the ferromagnetic state well below the curie temperature in each alloy. The thermal expansion coefficient increases with temperature more significantly in the paramagnetic states compared to the ferromagnetic states. The temperature dependence of the thermal expansion coefficient in the paramagnetic states is not much influenced by the type of alloying element. As a result, the lower the Tc is, the higher the thermal expansion coefficient tends to become in the paramagnetic states at high temperatures. Based on the results obtained, a way is proposed to design heat resistant ferritic steels with reduced thermal expansion coefficients; to add both Cr and Co as major alloying elements such that the Tc and the A3 temperatures are placed above their service temperature.

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The effect of the steam temperature fluctuations during steady state operation on the remnant life of the superheater header

Cited by 14 publications

References 1 publication

Development of life assessment procedures for power plant headers operated under flexible loading scenarios

Development of life assessment procedures for power plant headers operated under flexible loading scenarios

An online monitoring method for creep-fatigue life consumption with real-time damage accumulation

Reduction of Thermal Expansion of Ferritic/martensitic Heat Resistant Steels -Alloying Effects on Thermal Expansion of <i>α</i>-Fe Phase-

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