DOCSLIB.ORG

Investigation of Corrosion Fatigue Phenomena in Transient Zone of Mechanical Drive Steam Turbines and Its Preventive Measures

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Investigation of Corrosion Fatigue Phenomena in Transient Zone of Mechanical Drive Steam Turbines and Its Preventive Measures Proceedings of the Second Middle East Turbomachinery Symposium 17 – 20 March 2013, Doha, Qatar Investigation of Corrosion Fatigue Phenomena in Transient Zone of Mechanical Drive Steam Turbines and its Preventive Measures by Satoshi Hata Engineering and Design Division Mitsubishi Heavy Industries, Compressor Corporation Naoyuki Nagai Hiroshima Research & Development Center Mitsubishi Heavy Industries, Ltd. Norihito Fujimura MCO Saudi Arabia, LCC. (MCOSA) Mitsubishi Heavy Industries, Compressor Corporation Satoshi Hata ABSTRACT Satoshi Hata is a Group Manager For mechanical drive steam turbines, the investigation within the Turbo Machinery results of corrosion fatigue phenomena in the transient zone Engineering Department, Mitsubishi are introduced, including basic phenomena on expansion Heavy Industries, Ltd., in Hiroshima, line and actual design and damage experience. These results Japan. He has 30 year experience in were analyzed from the standpoint of stress intensity during R&D for nuclear uranium centrifuges, turbomolecular pumps, heavy-duty the start of cracking. In order to resolve such problems, gas turbines, steam turbines and preventive coating and blade design methods against fouling compressors. Mr. Hata has B.S., M.S. and corrosive environments are developed. Detailed and Ph.D. degrees (in Mechanical evaluation test results are given for coating performance Engineering) from Kyusyu Institute of using a unique test procedure simulating fouling phenomena Technology. and washing conditions. Finally, the results of the Naoyuki Nagai successful modification of internals and on-line washing Naoyuki Nagai is a Research Manager results on site are introduced. in the Research & Development Center, at Mitsubishi Heavy Industries, Ltd., in INTRODUCTION Hiroshima Japan. He has 27 year In petrochemical plants, the flow path of process gas experience in R&D and troubleshooting compressor drive steam turbines have several kinds of for rotor dynamics, torsional dynamics （1） involved in electromagnetic, control potential damage such as erosion and corrosion, resulting and aerodynamic coupling regarding in deterioration of performance and a decrease in strength about compressor, steam turbine and margin. Especially, in the process of steam expansion, driving system. Mr. Nagai received his depending on steam pressure and temperature, corrosive B.S. and M.S. degrees from Kyushu chemicals in very low levels of concentration tend to be Institute of Technology and Ph.D. from Hiroshima University (in Mech. enriched to a high level. These enriched chemicals deposit Engineering). on the internal parts of the steam turbine and cause a decrease in strength or blade failure（2）. Norihito Fujimura In this paper, the authors investigate the relationship Norihito Fujimura is an application between this enrichment zone, strength safety margin, and engineer of Engineering Department in blade failure, and the root causes according to analysis of Global Marketing & Sales Division, Mitsubishi Heavy Industries, actual blade failures. Based on these investigation results, Compressor Corporation, in Tokyo, the authors introduce blade structure improvements in Japan. He has eight years’ experience order to increase the safety margin for corrosion fatigue. in designing compressors and steam As one of the factors related to performance deterioration turbines. Mr. Fujimura has B.S and and operation restriction, fouling on nozzle and blade M.S degrees in Mechanical profiles has to be highlighted, and it is necessary to think Engineering from Oita University of some improvements for the prevention of fouling. The authors study surface treatment methods applicable to Copyright 8 2013 by Turbomachinery Laboratory, Texas A&M University Proceedings of the Second Middle East Turbomachinery Symposium 17 – 20 March 2013, Doha, Qatar actual blades to improve anti-corrosion and anti-fouling. Case Study of Typical Low Pressure Blade Damage and They also introduce a new surface treatment method and Root Cause Analysis the results of an evaluation test for coating functions, Figure 3 shows a typical failure of blades in the low including washing efficiency using a unique simulation test pressure section (tenon and finitely grouped type of L-1 set-up. Finally, the possibility of long-term effective stage) （5）. The tenon and shroud plate have failed. Detailed operation based on a combination of a new surface conditions of the fracture surface and crack propagation treatment method, new online washing system and special direction (arrows) are shown in Figure 4. This is flow path design is explained. conformed cracking initiated on the internal side of the tenon and this failure is HCF according to the observed Turbine Expansion Line and Typical Damage fine spacing striation（6）. In the physical process of the low pressure stages of a L-1Stage Damage steam turbine expanding from the superheated zone to the Portion saturated zone, possible causes of mechanical damage are shown in Figure 1. On dry and wet areas around the saturation line, we tend to observe SCC caused by high concentrated NaOH, pitting, corrosion fatigue related to NaCl enrichment in the special zone (Wilson zone) in which dry and wet conditions continuously occur in the moisture range of 2% to 6% and heavy drain erosion in high moisture zones of over 12%. As shown in Figure 2, a fatigue endurance limit for 13Cr stainless steel under Figure 3 Typical Blade Damage of LP Section NaCl distilled water decreases drastically, and in this b) Inlet side Wilson zone we have to pay particular attention to blade Point A design, whilst considering the critical importance of controlling impurities in steam for actual continuous a) operation. It is necessary to understand the corrosive environment in actual operation to evaluate fatigue life. However, it is very difficult to expect concentration level Crack changes of corrosive chemicals under conditions of rapid propagating expansion in complicated high velocity flow fields. In this direction Concave side Concave sense, it is important to evaluate mechanical integrity with side Convex a combination of detailed static and dynamic stress analysis and operation experience. Outlet side LP Turbine Inlet Figure 4 Crack Propagation on Fracture Surface Caustic SCC NaOH,Oxides Pitting, SCC,Corrosion Fatigue Detailed fracture and stress analyses of the actual blade are - 2- 2- Salt Zone Cl , SO4 , CO3 ,O2, CuO, Acetate carried out by root cause analysis, which is shown in Drying on Hot Surfaces Figure 5. Key factors involved in this failure could include ～30% NaCl Solution S excessive static and dynamic external forces, and a C at Enthalpy O ura 2 C tion or L A ro ine decrease in the fatigue endurance limit in a corrosive c E si id ro on > s, s V < ion 2% el pH oc environment. It is also important to evaluate resonance it Enrichment Zone y 4% W stress in the variable speed range in such a corrosive （ ） a Wilson Zone te r 6% Moisture Dr op environment. le t Er 8% os io Over Speed Large Centrifugal Force n 10% Excessive 12% Static Stress Large Stress Concentration （3） Figure 1. Turbine Expansion Line and Typical Damage Harmonic Resonance High Order Nozzle Wake Resonance Low Damping / High Response Excessive 500 Smooth and notched bar specimens Vibration Stress Over Load / Large Turbulence 18℃ 60 Hz Air Blade 400 Large Stress Concentration Distilled Water Failure NaCl(％) 300 3 Fretting on Contact Surface × -1 3 10 3×10-2 -3 200 3×10 -4 Insufficient Mechanical Property 3×10 Inferior Material 100 80℃ Defects of Material 3 0 104 105 106 107 108 109 Insufficient Quality of Steam （20） （200） （0.002） （0.02） （0.2） （2） Rotating bending stressRotating (MPa) Corrosive Number of cycles (Days) Corrosive Chemicals Enrichment Environment Fatigue Endurance Limit Decrease Figure 2. Decrease of Fatigue Endurance Limit for 13Cr Stainless Steel under NaCl Distilled Water（4） Figure 5 Root Cause Analysis for Blade Damage Copyright 8 2013 by Turbomachinery Laboratory, Texas A&M University Proceedings of the Second Middle East Turbomachinery Symposium 17 – 20 March 2013, Doha, Qatar Enrichment of Corrosive Chemicals in Steam and Point C Corrosion Fatigue j i In order to investigate the relationship between corrosion Na : 3100ppm Na : 4000ppm Cl : 4000ppm Cl : 1800ppm fatigue and the wet/dry transient zone, a detailed analysis K : 1700ppm 890μm from surface 640μm from surface of the fracture surface and corrosion chemicals deposited on an actual damaged rotor is carried out. Fracture surface As a result of the fracture surface analysis shown in Figure h k g Na : 2400ppm Na : 1900ppm Cl : 3700ppm 6, the typical corrosion pits of diameter about 20 Cl : 1700ppm Cl : 3000ppm K : 1500ppm K : 800ppm K : 1100ppm 103μm from surface 70μm from surface 69μm from surface micrometers in diameter are observed around the fatigue Fracture surface crack starting point. Though corrosion fatigue includes environmental factors, it is difficult to quantitatively Figure 8 Corrosive Chemicals Concentration of Deposits estimate the actual operating condition affecting the fatigue on Fracture Surface limit, and there are a lot of other unclear factors. A basic mechanism of corrosion fatigue is explained in Figure 7（9） In addition, the same corrosion pits are observed on the （16）. This corrosion fatigue phenomenon is affected by tenon, blade profile, and root of sound blades of the same certain types of chemical materials and their concentration stage and turbine as shown in Figure 9. Inside these pits, levels, and it is thought
Load more

Recommended publications
  • Corrosion Fatigue: Type 304 Stainless Steel in Acid-Chloride and Implant Metals in Biological Fluid
    76-9939 BOWERS, Davtd Francis, 1937- CORROSION FATIGUE: TYPE 304 STAINLESS STEEL IN ACID-CHLORIDE AND IMPLANT METALS IN BIOLOGICAL FLUID. The Ohio State University, Ph.D., 1975 Engineering, metallurgy Xerox University Microfilms, Ann Arbor, Michigan 48ioe CORROSION FATIGUE: TYPE 304 STAINLESS STEEL IN ACID-CHLORIDE AND IMPLANT METALS IN BIOLOGICAL FLUID Dissertation Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University by David Francis Bowers, B.S., M.S. Metallurgical Engineering The Ohio State University 1975 Approved by (dviser Department of Metallurgical Engineering Reading Committee: Dr. Mars G. Fontana Dr. Frank Beck Dr. John P. Hirth To My Wife and Daughter TABLE OF CONTENTS Page ACKNOWLEDGEMENTS.......................................... iv VITA........................................................ vi LIST OF TABLES............................................. viii LIST OF FIGURES... ...................... x INTRODUCTION.................. .. ......................... 1 I. LITERATURE SURVEY..................... 4 1.1 Concepts and Theory of Fatigue Crack Growth.. 4 1.2 Fracture Mechanics Approach to Crack Growth in Engineering Structures..................... 18 1.3 Effect of Microstructure on Fatigue Cracking Growth................................ 24 1.4 Mechanical Variables in Corrosion Fatigue.... 41 1.5 Environmental Interaction with Fatigue Crack Growth.................................... 59 II. EXPERIMENTAL DETAILS...............................
    [Show full text]
  • Top Performance When the Going Gets Tough
    Top performance when the going gets tough The Alfa Laval DuroShell plate-and-shell heat exchanger Sub-headline coming soon DuroShell – plate-and-shell made tougher Alfa Laval DuroShell is a specially engineered plate-and-shell heat exchanger ideal for demanding duties and corrosive media. Able to withstand fatigue even at high temperatures and pressures, it outperforms not only traditional heat exchangers, but also other plate-and-shells. As flexible as it is strong DuroShell creates new possibilities through its com- pactness, efficiency and exceptional resistance to fatigue. Able to work with liquids, gases and two- phase mixtures, it stands out among heat exchangers in its duty range. DuroShell handles pressures up to 100 barg (1450 psig) in compliance with PED and ASME, and temperatures as high as 450 °C (842 °F). Built for your application DuroShell is fully welded and gasket-free, with internal features that make it still more robust. Plates are avail- able in 316L stainless steel, while the pressure vessel itself can be built in 316L stainless steel or carbon steel. Three different sizes are possible, with heat transfer surfaces ranging 2–235 m2 (21.5–2530 ft 2) in area. DuroShell RollerCoaster Robust and efficient performance. DuroShell PowerPack Optimized flow distribution and fatigue resistance. Learn more at www.alfalaval.com/duroshell Plate-and-shell benefits made better • More uptime and longer life due to • Installation savings through even greater fatigue resistance more compact, lightweight design • Higher operating pressures thanks • Greater reliability as a result of to robust, patented construction closed, fully welded construction • Operational gains created by 15–20 % higher thermal efficiency How it works Revolutionary technology Optimized flow DuroShell is a plate-and-shell heat exchanger, but one DuroShell operates with one media on the plate side with a unique internal design.
    [Show full text]
  • Corrosion-Fatigue Evaluation of Uncoated Weathering Steel Bridges
    applied sciences Article Corrosion-Fatigue Evaluation of Uncoated Weathering Steel Bridges Yu Zhang, Kaifeng Zheng, Junlin Heng * and Jin Zhu Department of Bridge Engineering, School of Civil Engineering, Southwest Jiaotong University, Chengdu 610031, China * Correspondence: [email protected]; Tel.: +86-182-8017-6652 Received: 19 July 2019; Accepted: 19 August 2019; Published: 22 August 2019 Featured Application: The new findings highlight the enhancement in corrosion-fatigue performance of steel bridges by using the uncoated weathering steel. Besides, an innovative approach has been established to simulate the corrosion-fatigue process in uncoated weathering steel bridges, providing deep insights into the service life of the bridges. The approaches suggested in the article can be used (not limited to) as a reference for the research and design of uncoated weathering steel bridges. Abstract: Uncoated weathering steel (UWS) bridges have been extensively used to reduce the lifecycle cost since they are maintenance-free and eco-friendly. However, the fatigue issue becomes significant in UWS bridges due to the intended corrosion process utilized to form the corrodent-proof rust layer instead of the coating process. In this paper, an innovative model is proposed to simulate the corrosion-fatigue (C-F) process in UWS bridges. Generally, the C-F process could be considered as two relatively independent stages in a time series, including the pitting process of flaw-initiation and the fatigue crack propagation of the critical pitting flaw. In the proposed C-F model, Faraday’s law has been employed at the critical flaw-initiation stage to describe the pitting process, in which the pitting current is applied to reflect the pitting rate in different corrosive environments.
    [Show full text]
  • Fatigue Overview Introduction to Fatigue Analysis
    Fatigue overview Introduction to fatigue analysis • Fatigue is the failure of a component after several repetitive load cycles. • As a one-time occurrence, the load is not dangerous in itself. Over time the alternating load is able to break the structure anyway. • It is estimated that between 50 and 90 % of product failures is caused by fatigue, and based on this fact, fatigue evaluation should be a part of all product development. What is fatigue? In materials science, fatigue is the progressive and localized structural damage that occurs when a material is subjected to cyclic loading (material is stressed repeatedly). Clients tous différents Routes de qualités variables Contraintes Fatigue Design in Automotive Industry Conception fiable PSA (Peugeot Citroën) Résistances 3s 3s Dispersion matériau Dispersion de production Fatigue • Fracture mechanics can be divided into three stages: 1. Crack nucleation 2. Crack-growth 3. Ultimate ductile failure Introduction to fatigue analysis • Fatigue is the failure of a component after several repetitive load cycles. • As a one-time occurrence, the load is not dangerous in itself. Over time the alternating load is able to break the structure anyway. • It is estimated that between 50 and 90 % of product failures is caused by fatigue, and based on this fact, fatigue evaluation should be a part of all product development. Historical background • In comparison to the classical stress analysis, fatigue theory is a relative new phenomenon. The need to understand fatigue arose after the industrial revolution introduced steel structures. Three areas were particularly involved in early failures: Railway trains, Mining equipment and Bridges. Historical background • 1837: Wilhelm Albert publishes the first article on fatigue.
    [Show full text]
  • Corrosion Fatigue of Austenitic Stainless Steels for Nuclear Power Engineering
    metals Article Corrosion Fatigue of Austenitic Stainless Steels for Nuclear Power Engineering Irena Vlˇcková 1,*, Petr Jonšta 2, ZdenˇekJonšta 2, Petra Vá ˇnová 2 and Tat’ána Kulová 2 1 RMTSC, Material & Metallurgical Research Ltd., Remote Site Ostrava, VÚHŽ a.s., Dobrá 739 51, Czech Republic 2 Department of Materials Engineering, VŠB-Technical University of Ostrava, Ostrava 708 33, Czech Republic; [email protected] (P.J.); [email protected] (Z.J.); [email protected] (P.V.); [email protected] (T.K.) * Correspondence: [email protected]; Tel.: +420-558601257 Academic Editor: Hugo F. Lopez Received: 21 September 2016; Accepted: 8 December 2016; Published: 16 December 2016 Abstract: Significant structural steels for nuclear power engineering are chromium-nickel austenitic stainless steels. The presented paper evaluates the kinetics of the fatigue crack growth of AISI 304L and AISI 316L stainless steels in air and in corrosive environments of 3.5% aqueous NaCl solution after the application of solution annealing, stabilizing annealing, and sensitization annealing. Comparisons were made between the fatigue crack growth rate after each heat treatment regime, and a comparison between the fatigue crack growth rate in both types of steels was made. For individual heat treatment regimes, the possibility of the development of intergranular corrosion was also considered. Evaluations resulted in very favourable corrosion fatigue characteristics of the 316L steel. After application of solution and stabilizing annealing at a comparable DK level, the fatigue crack growth rate was about one half compared to 304L steel. After sensitization annealing of 316L steel, compared to stabilizing annealing, the increase of crack growth rate during corrosion fatigue was slightly higher.
    [Show full text]
  • Design for Cyclic Loading, Soderberg, Goodman and Modified Goodman's Equation
    Design for Cyclic Loading 1. Completely reversing cyclic stress and endurance strength A purely reversing or cyclic stress means when the stress alternates between equal positive and Pure cyclic stress negative peak stresses sinusoidally during each 300 cycle of operation, as shown. In this diagram the stress varies with time between +250 MPa 200 to -250MPa. This kind of cyclic stress is 100 developed in many rotating machine parts that 0 are carrying a constant bending load. -100 When a part is subjected cyclic stress, Stress (MPa) also known as range or reversing stress (Sr), it -200 has been observed that the failure of the part -300 occurs after a number of stress reversals (N) time even it the magnitude of Sr is below the material’s yield strength. Generally, higher the value of Sr, lesser N is needed for failure. No. of Cyclic stress stress (Sr) reversals for failure (N) psi 1000 81000 2000 75465 4000 70307 8000 65501 16000 61024 32000 56853 64000 52967 96000 50818 144000 48757 216000 46779 324000 44881 486000 43060 729000 41313 1000000 40000 For a typical material, the table and the graph above (S-N curve) show the relationship between the magnitudes Sr and the number of stress reversals (N) before failure of the part. For example, if the part were subjected to Sr= 81,000 psi, then it would fail after N=1000 stress reversals. If the same part is subjected to Sr = 61,024 psi, then it can survive up to N=16,000 reversals, and so on. Sengupta MET 301: Design for Cyclic Loading 1 of 7 It has been observed that for most of engineering materials, the rate of reduction of Sr becomes negligible near the vicinity of N = 106 and the slope of the S-N curve becomes more or less horizontal.
    [Show full text]
  • The Environmental Effect on Corrosion Fatigue Behavior of Austenitic Stainless Steels
    The Environmental Effect on Corrosion Fatigue Behavior of Austenitic Stainless Steels by Lun Yu B.S. Nuclear Engineering (2013) Shanghai Jiao Tong University SUBMITTED TO THE DEPARTMENT OF NUCLEAR SCIENCE AND ENGINEERING IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY IN NUCLEAR SCIENCE AND ENGINEERING AT THE MASSACHUSETTS INSTITUTE OF TECHNOLOGY September, 2017 © 2017 Massachusetts Institute of Technology. All rights reserved. Signature of Author: _____________________________________________________________ Lun Yu Department of Nuclear Science and Engineering August 25, 2017 Certified by: __________________________________________________________________ Ronald G. Ballinger Professor of Nuclear Science and Engineering, Materials Science and Engineering Thesis Supervisor Certified by: ___________________________________________________________________ Michael P. Short Assistant Professor of Nuclear Science and Engineering Thesis Reader Accepted by: ___________________________________________________________________ Ju Li Battelle Energy Alliance Professor of Nuclear Science and Engineering, Professor of Materials Science and Engineering Chair, Department Committee on Graduate Students This page was left blank intentionally The Environmental Effect on Corrosion Fatigue Behavior of Austenitic Stainless Steels by Lun Yu Submitted to the Department of Nuclear Science and Engineering on September 1, 2017 in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy in Nuclear Science and
    [Show full text]
  • Very High Cycle Fatigue of Engineering Materials
    Faculty of Technology and Science Materials Engineering Vitaliy Kazymyrovych Very high cycle fatigue of engineering materials (A literature review) Karlstad University Studies 2009:22 Vitaliy Kazymyrovych Very high cycle fatigue of engineering materials (A literature review) Karlstad University Studies 2009:22 Vitaliy Kazymyrovych. Very high cycle fatigue of engineering materials - A literature review Research Report Karlstad University Studies 2009:22 ISSN 1403-8099 ISBN 978-91-7063-246-4 © The Author Distribution: Faculty of Technology and Science Materials Engineering SE-651 88 Karlstad +46 54 700 10 00 www.kau.se Printed at: Universitetstryckeriet, Karlstad 2009 Very high cycle fatigue of engineering materials (A literature review) V.Kazymyrovych* Department of Materials Engineering, Karlstad University SE-651 88, Sweden * Email address: [email protected] Abstract This paper examines the development and present status of the Very High Cycle Fatigue (VHCF) phenomenon in engineering materials. The concept of ultrasonic fatigue testing is described in light of its historical appearance covering the main principles and equipment variations. The VHCF behaviour of the most important materials used for very long life applications is presented, with particular attention paid to steels. In section 3 the VHCF properties of titanium-, nickel-, aluminium- and magnesium alloys are described. Furthermore, the typical fatigue behaviour and mechanisms of pure metals are presented. Section 4 examines the VHCF properties of various types of steels e.g. low carbon steel, spring steel, stainless steel, bearing steel as well as tool steel. In addition to this, the main material defects that initiate VHCF failure are examined in this study. Furthermore, the different stages characteristic for fatigue crack development in VHCF are described in section 5 in terms of relative importance and sequence.
    [Show full text]
  • 10Th International Congress on Marine Corrosion and Fouling, University of Melbourne, February 1999
    10th International Congress on Marine Corrosion and Fouling, University of Melbourne, February 1999 Additional Papers John A Lewis (Editor) Maritime Platforms Division Aeronautical and Maritime Research Laboratory DSTO-GD-0287 ABSTRACT This volume contains nineteen papers from the 10th International Congress on Marine Corrosion and Fouling, held at the University of Melbourne in Melbourne, Australia, in February 1999. The scope of the congress was to enhance scientific understanding of the processes and prevention of chemical and biological degradation of materials in the sea. Papers in this volume range across the themes of marine biofilms and bioadhesion, macrofouling processes and effects, methods for prevention of marine fouling, biocides in the marine environment, biodeterioration of wood in the sea, and marine corrosion. RELEASE LIMITATION Approved for public release Published by DSTO Aeronautical and Maritime Research Laboratory 506 Lorimer St Fishermans Bend, Victoria 3207 Australia Telephone: (03) 9626 7000 Fax: (03) 9626 7999 © Commonwealth of Australia 2001 AR-011-880 May 2001 APPROVED FOR PUBLIC RELEASE 10th International Congress on Marine Corrosion and Fouling, University of Melbourne, February 1999 Additional Papers Executive Summary The fouling and corrosion of vessels and structures immersed in the sea continues to pose significant economic and operational costs to the owner. Fouling growth can interfere with the operation of submerged equipment, impose increased loading stresses and accelerate corrosion on marine structures, and adversely affect the performance of ships by increasing hydrodynamic drag, which necessitates the use of more power and fuel to move the ship through the water. Similarly, marine corrosion and biodegradation of materials can compromise the operation and structural integrity of vessels, structures and other immersed equipment.
    [Show full text]
  • Four Types of Heat Exchanger Failures
    Four Types of Heat Exchanger Failures . mechanical, chemically induced corrosion, combination of mechanical and chemically induced corrosion, and scale, mud, and algae fouling By MARVIN P. SCHWARTZ, Chief Product Engineer, ITT Bell & Gossett a unit of Fluid Handling Div., International Telephone & Telegraph Corp , Skokie IL Hcat exchangers usually provide a long service life with Maximum recommended velocity in the tubes and little or no maintenance because they do not contain any entrance nozzle is a function of many variables, including moving parts. However, there are four types of heat tube material, fluid handled, and temperature. Materials exchanger failures that can occur, and can usually be such as steel, stainless steel, and copper-nickel withstand prevented: mechanical, chemically induced corrosion, higher tube velocities than copper. Copper is normally combination of mechanical and chemically induced limited to 7.5 fps; the other materials can handle 10 or 11 corrosion, and scale, mud. and algae fouling. fps. If water is flowing through copper tubing, the velocity This article provides the plant engineer with a detailed should be less than 7.5 fps when it contains suspended look at the problems that can develop and describes the solids or is softened. corrective actions that should be taken to prevent them. Erosion problems on the outside of tubes usually result Mechanical-These failures can take seven different from impingement of wet, high-velocity gases, such as forms: metal erosion, steam or water hammer, vibration, steam. Wet gas impingement is controlled by oversizing thermal fatigue, freeze-up, thermal expansion. and loss of inlet nozzles, or by placing impingement baffles in the cooling water.
    [Show full text]
  • Creep-Fatigue Failure Diagnosis
    Review Creep-Fatigue Failure Diagnosis Stuart Holdsworth Received: 22 October 2015 ; Accepted: 6 November 2015 ; Published: 16 November 2015 Academic Editor: Robert Lancaster EMPA: Swiss Federal Laboratories for Materials Science and Technology Überlandstrasse 129, Dübendorf CH-8600, Switzerland; [email protected]; Tel.: +41-58-765-47-32 Abstract: Failure diagnosis invariably involves consideration of both associated material condition and the results of a mechanical analysis of prior operating history. This Review focuses on these aspects with particular reference to creep-fatigue failure diagnosis. Creep-fatigue cracking can be due to a spectrum of loading conditions ranging from pure cyclic to mainly steady loading with infrequent off-load transients. These require a range of mechanical analysis approaches, a number of which are reviewed. The microstructural information revealing material condition can vary with alloy class. In practice, the detail of the consequent cracking mechanism(s) can be camouflaged by oxidation at high temperatures, although the presence of oxide on fracture surfaces can be used to date events leading to failure. Routine laboratory specimen post-test examination is strongly recommended to characterise the detail of deformation and damage accumulation under known and well-controlled loading conditions to improve the effectiveness and efficiency of failure diagnosis. Keywords: failure diagnosis; creep-fatigue; material condition; mechanical analysis 1. Introduction The diagnosis of failures invariably involves consideration of both the associated material condition and the results of a mechanical analysis of prior operating history. Material condition refers not only to a knowledge of the chemical composition and mechanical properties relative to those originally specified for the failed component, but also the appearance and extent of microstructural and physical damage responsible for failure.
    [Show full text]
  • Creep, Fatigue and Creep-Fatigue Interactions in Modified 9% Cr - 1% Mo (P91) Steels" (2013)
    University of Arkansas, Fayetteville ScholarWorks@UARK Theses and Dissertations 5-2013 Creep, Fatigue and Creep-Fatigue Interactions in Modified 9% rC - 1% Mo (P91) Steels Valliappa Kalyanasundaram University of Arkansas, Fayetteville Follow this and additional works at: http://scholarworks.uark.edu/etd Part of the Mechanics of Materials Commons, Structural Engineering Commons, and the Structural Materials Commons Recommended Citation Kalyanasundaram, Valliappa, "Creep, Fatigue and Creep-Fatigue Interactions in Modified 9% Cr - 1% Mo (P91) Steels" (2013). Theses and Dissertations. 692. http://scholarworks.uark.edu/etd/692 This Dissertation is brought to you for free and open access by ScholarWorks@UARK. It has been accepted for inclusion in Theses and Dissertations by an authorized administrator of ScholarWorks@UARK. For more information, please contact [email protected], [email protected]. CREEP, FATIGUE AND CREEP-FATIGUE INTERACTIONS IN MODIFIED 9% Cr – 1% Mo (P91) STEELS CREEP, FATIGUE AND CREEP-FATIGUE INTERACTIONS IN MODIFIED 9% Cr – 1% Mo (P91) STEELS A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Mechanical Engineering By Valliappa Kalyanasundaram Madurai Kamaraj University Bachelor of Engineering in Mechanical Engineering, 2004 University of Arkansas Master of Science in Mechanical Engineering, 2008 May 2013 University of Arkansas ABSTRACT Grade P91 steel, from the class of advanced high-chrome ferritic steels, is one of the preferred materials for many elevated temperature structural components. Creep-fatigue (C-F) interactions, along with oxidation, can accelerate the kinetics of damage accumulation and consequently reduce such components’ life. Hence, reliable C-F test data is required for meticulous consideration of C-F interactions and oxidation, which in turn is vital for sound design practices.
    [Show full text]