Steam Generator Grade P91 Steel Components Creep-Assessment Through a Procedure for the Italian Code Application and Comparison With the ECCC Recommendations, American Standard

2017 ◽  
Author(s):  
Ottaviano Grisolia ◽  
Lorenzo Scano
Keyword(s):  
High Temperature ◽  
Steam Generator ◽  
Polynomial Function ◽  
Steam Generators ◽  
Steel Microstructure ◽  
Operation Temperature ◽  
Creep Analysis ◽  
Material Creep ◽  
Level 3 ◽  
American Standard

ASTM A 335-Grade P91 components of steam generators may be critical because of possible steel microstructure changes and/or embrittlement due to the FATT increase during service at high temperature: both phenomena may worsen the material creep behavior globally. Operation temperatures below 600°C such as in the worked case considered herein should be less critical; nevertheless, the worked case plan has included additional controls on microstructure also to have a reference for the future. Present study considers for the worked case steam generator the creep analysis of high-temperature-section (superheater / reheater) two components, outflow tubing and manifold: they may be critical because of the long continued service (110,000 hours or twelve years) and loading conditions (maximum operation temperature and applied stress at the intersection). Aim of the work is to compare life results from the Italian creep code with those predicted by the API 579-1; it also checks compatibility of results from the polynomial models in Italian, ECCC and API 579-1 procedures. Life results based on the Italian-code polynomial function are consistent with those based on the polynomial function proposed in ECCC: With preliminary stresses from pressure formulas, life estimates are a bit more conservative than the ECCC model’s. Finally, life results obtained through the API 579-1 Level 3 assessment appear consistent with those predicted by the Italian creep code, ECCC recommendations application.

Steam Generator Grade P91 Steel Components Creep-Assessment By Test After Extended Service

2021 ◽  
Author(s):  
Ottaviano Grisolia ◽  
Lorenzo Scano ◽  
Francesco Piccini ◽  
Antonietta Lo Conte ◽  
Massimiliano De Agostinis ◽  
...  
Keyword(s):  
High Temperature ◽  
Weld Metal ◽  
Steam Generator ◽  
Microstructure Evolution ◽  
Creep Strength ◽  
Operation Temperature ◽  
Creep Analysis ◽  
Creep Cavitation ◽  
Weld Metal Microstructure ◽  
Metal Microstructure

Abstract Previous study carried out creep analysis for steam generator high-temperature-section two components, outflow tubing and manifold of the superheater harp: they may have been critical because of the long continued service (109,000 hours or twelve years) and loading conditions, including maximum operation temperature (565°C) and applied stress (65 MPa). Metallographic methods by replica had showed no evidence of the creep cavitation in all the positions considered for both tubing and manifold. In particular, they had not found any cavitation or phases affecting creep strength of the material in the base, HAZ and weld metal microstructure. Now, present study carries out investigation for the two components based on the next plant outage outcome, after further 20,000-hours service. Both metallographic methods and hardness measurements’ results would compare with previous ones providing microstructure evolution in the period.

HRSG Header Creep-Assessment Through a Procedure for the Italian Code Application and Comparison With the American Standard

2015 ◽  
Author(s):  
Ottaviano Grisolia ◽  
Lorenzo Scano
Keyword(s):  
Weight Fraction ◽  
External Loading ◽  
Creep Life ◽  
Element Analysis ◽  
Creep Analysis ◽  
Level 3 ◽  
Approach Method ◽  
American Standard ◽  
Level 1 ◽  
Minimum Stress

Lower headers of bottom-supported heat-recovery steam generators (HRSG) may be critical because of their longitudinal dimensions, thermal expansions and external loading (the harp’s weight): Present work considers the creep analysis of the high-temperature-section (superheater /reheater) headers: they may be critical because of the long continued service (175000 hours or twenty years), larger dimensions and the external loads, including a negligible steam-drum weight fraction. The aim of the work is to compare life results from the Italian creep code with those predicted by the American standard API 579-1. This work also checks the compatibility of results coming from the two polynomial models in both Italian and API 579-1 procedures. Classical methods, applied using both ASME and Italian pressure formulae, show that, as for the evaporator-section header, the pressure contribution to longitudinal stress may be greater than bending alone; considering now the increased header’s weight, the stress ratio is also comparable to the evaporator’s. Consistency of results from numerical-model stress analysis (elastic) is good, confirming the pressure contribution is greatest. For the Level-1 assessment (B31.1 stresses), the Italian procedure and the API 579-1 return consistent creep life results, though the API 579-1 results appear more conservative than the Italian-procedure’s. Level-1 assessment, acted through an elastic finite element analysis (FEA), uses Larson-Miller parameter (LMP)-approach method with minimum stress-to-rupture data: the Italian procedure and API 579-1 return consistent creep life results when evaluated on the tubehole branch side, Italian-procedure’s appearing little more conservative than the API 579-1’s. For the Level-2 assessment (FEA stresses), again the Italian procedure and the API 579-1 return consistent creep life results with the Italian-procedure ones again a little more conservative than the API 579-1’s for both sides of the intersection. Level-3 assessment (incorporating creep, plasticity and relaxation) shows (short) creep lives similar to Italian-procedure’s.

Parametric Study of External Pressure on Steam Generator Tube Bends

2012 ◽  
Author(s):  
Mitch Hokazono ◽  
Clayton T. Smith
Keyword(s):  
Steam Generator ◽  
Parametric Study ◽  
External Pressure ◽  
Light Water Reactor ◽  
Material Strength ◽  
Steam Generators ◽  
Elliptical Cross ◽  
Light Water ◽  
Water Reactor ◽  
Steam Generator Tubes

Integral light-water reactor designs propose the use of steam generators located within the reactor vessel. Steam generator tubes in these designs must withstand external pressure loadings to prevent buckling, which is affected by material strength, fabrication techniques, chemical environment and tube geometry. Experience with fired tube boilers has shown that buckling in boiler tubes is greatly alleviated by controlling ovality in bends when the tubes are fabricated. Light water reactor steam generator pressures will not cause a buckling problem in steam generators with reasonable fabrication limits on tube ovality and wall thinning. Utilizing existing Code rules, there is a significant design margin, even for the maximum differential pressure case. With reasonable bend design and fabrication limits the helical steam generator thermodynamic advantages can be realized without a buckling concern. This paper describes a theoretical methodology for determining allowable external pressure for steam generator tubes subject to tube ovality based on ASME Section III Code Case N-759-2 rules. A parametric study of the results of this methodology applied to an elliptical cross section with varying wall thicknesses, tube diameters, and ovality values is also presented.

scholarly journals Gas Turbine Heat Recovery Steam Generators for Combined Cycles Natural or Forced Circulation Considerations

1988 ◽  
Author(s):  
Akber Pasha
Keyword(s):  
Gas Turbine ◽  
Steam Generator ◽  
Heat Recovery ◽  
Power Plants ◽  
Natural Circulation ◽  
Combined Cycle ◽  
Heat Recovery Steam Generator ◽  
Steam Generators ◽  
Forced Circulation ◽  
Gas Turbine Exhaust

In recent years the combined cycle has become a very attractive power plant arrangement because of its high cycle efficiency, short order-to-on-line time and flexibility in the sizing when compared to conventional steam power plants. However, optimization of the cycle and selection of combined cycle equipment has become more complex because the three major components, Gas Turbine, Heat Recovery Steam Generator and Steam Turbine, are often designed and built by different manufacturers. Heat Recovery Steam Generators are classified into two major categories — 1) Natural Circulation and 2) Forced Circulation. Both circulation designs have certain advantages, disadvantages and limitations. This paper analyzes various factors including; availability, start-up, gas turbine exhaust conditions, reliability, space requirements, etc., which are affected by the type of circulation and which in turn affect the design, price and performance of the Heat Recovery Steam Generator. Modern trends around the world are discussed and conclusions are drawn as to the best type of circulation for a Heat Recovery Steam Generator for combined cycle application.

Crack Growth Prediction and Leakage Potential of Steam Generator Tubes Subjected to Flow Induced Vibrations

2014 ◽  
Author(s):  
Salim El Bouzidi ◽  
Marwan Hassan ◽  
Jovica Riznic
Keyword(s):  
Crack Growth ◽  
Steam Generator ◽  
Power Plants ◽  
Mechanical Energy ◽  
Steam Generators ◽  
Two Phase ◽  
Element Analysis ◽  
Wide Range ◽  
Flow Induced Vibrations ◽  
Crack Growth Model

Nuclear steam generators are critical components of nuclear power plants. Flow-Induced Vibrations (FIV) are a major threat to the operation of nuclear steam generators. The two main manifestations of FIV in heat exchangers are turbulence and fluidelastic instability, which would add mechanical energy to the system resulting in great levels of vibrations. The consequences on the operation of steam generators are premature wear of the tubes, as well as development of cracks that may leak radioactive heavy water. This paper investigates the effect of tube support clearance on crack propagation. A crack growth model is used to simulate the growth of Surface Flaws and Through-Wall Cracks of various initial sizes due to a wide range of support clearances. Leakage rates are predicted using a two-phase flow leakage model. Non-linear finite element analysis is used to simulate a full U-bend subjected to fluidelastic and turbulence forces. Monte Carlo Simulations are then used to conduct a probabilistic assessment of steam generator life due to crack development.

scholarly journals Numerical discretization analysis of a HTR steam generator model for the thermal-hydraulics code trace

2014 ◽  
Vol 29 (suppl.) ◽  
pp. 31-38 ◽  
Author(s):  
Markus Esch ◽  
Dietrich Knoche ◽  
Antonio Hurtado
Keyword(s):  
High Temperature ◽  
Steam Generator ◽  
Electricity Production ◽  
Thermal Hydraulics ◽  
The Past ◽  
Crucial Component ◽  
High Temperature Reactor ◽  
Different Diameters ◽  
Typical Design ◽  
Steam Generator Model

For future high temperature reactor projects, e. g., for electricity production or nuclear process heat applications, the steam generator is a crucial component. A typical design is a helical coil steam generator consisting of several tubes connected in parallel forming cylinders of different diameters. This type of steam generator was a significant component used at the thorium high temperature reactor. In the work presented the temperature profile is being analyzed by the nodal thermal hydraulics code TRACE for the thorium high temperature reactor steam generator. The influence of the nodalization is being investigated within the scope of this study and compared to experimental results from the past. The results of the standard TRACE code are compared to results using a modified Nusselt number for the primary side. The implemented heat transfer correlation was developed within the past German HTR program. This study shows that both TRACE versions are stable and provides a discussion of the nodalization requirements.

scholarly journals Features of thermodynamic and thermal processes in hydrogen combustion units and systems on their basis

2021 ◽  
Vol 2039 (1) ◽  
pp. 012032
Author(s):  
A I Schastlivtsev ◽  
V I Borzenko
Keyword(s):  
High Temperature ◽  
Combustion Products ◽  
Hydrogen Combustion ◽  
Thermal Processes ◽  
Steam Generators ◽  
Temperature Combustion ◽  
Main Components ◽  
High Temperature Combustion

Abstract The main types and designs of hydrogen combustion units (HCU), including hydrogen-oxygen steam generators, superheaters and air heaters of various power levels, are considered. The main problems arising in the development, creation and testing of such installations are determined, including the problems of cooling the most heat-stressed units, mixing of the main components of the fuel and oxidizer, mixing of high-temperature combustion products and ballasting components, problems associated with the completeness of hydrogen combustion and ensuring safety during operation.

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