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steam turbine blade crack
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Cracks were analysed at the root of the third blade row of low-pressure steam turbine blades of different natural frequencies. The root cause of the fatigue crack initiation was pitting corrosion of the forged ferritic/martensitic X20Cr13 material. Metallographic investigations, finite element analysis and fracture mechanics. A crack of the fourth stage blade in a low-pressure turbine of a 500 MW steam turbine is studied. From non-destructive inspection, the crack was found at the leading edge vane of the fourth stage blade. Material composition analysis, hardness measurement and microstructure analysis were performed to study the cause. An increasing number of low-pressure steam turbines—especially at supercritical fossil units—have experienced stress corrosion cracking in the blade attachment region of their low-pressure rotors. Approaches to solving this problem range from redesign of the attachment and blade replacement to in-situ. The analysed blades belongs to the 27th stage of a 200 MW power steam turbine with operation time t="92245" hours. Fatigue failures of blades in rotating turbine disk were detected in service. Their fracture was the result of fatigue crack initiation and propagation up to the formation of a critical crack. In all of these failures,. ABSTRACT. This review paper discusses with the basic of corrosion and problem solutions. The operating life of a steam turbine largely depends on the mechanical and chemical properties materials used for turbine blades. Major steam turbine problems, such as stress corrosion, cracking of rotors and discs, corrosion. final failure. In this work, the results of fatigue tests on 12% Cr martensitic stainless steel, which is a standard blade material in the low pressure part of a steam turbine, are presented. The influence of corrosion pits and environment on the fatigue limit is investigated. Pit-to-crack transition is studied by optical observation and. The study of vibration response of a turbine blade helps the crack presence in a blade which alters its dynamic characteristics. The change is characterized by changes in the modal parameters associated with natural frequencies. In this paper, comparison of vibration response is made between first stage LP steam turbine. Long crack growth rates for steam turbine steels are now quite well quantified for a range of environmental conditions relevant to steam turbine operation. However there has been little focused research to determine the kinetics of growth in the short crack regime i.e. crack depths typically less than 500 micron. To address. Typical Blade Attachment SCC Failure Locations Background Stress corrosion cracking (SCC) of low-pressure steam turbine rotor blade attachments is an industry issue on older fossil and nuclear units. Many units have experienced forced outages and/or extended repairs due to direct or collateral damage. Cracks that. In case of a low pressure steam turbine the crack like flaws due to low cycle fatigue (LCF) is one of the main reasons for its premature failure as reporte. In order to evaluate the environmentally assisted cracking (EAC) susceptibility of three possible alloys, 16Cr-4Ni, 12Cr, and 13Cr, to be used as turbine blade materials for a geothermal power plants, corrosion fatigue tests were performed in simulated condensed geothermal environment without H2S. EAC includes an. In fact, the cost of turbine losses induced by blade and dovetail cracking alone was more than 40% of the total turbine loss value based on an earlier FM Global study [1], consistent with the “Handbook of Loss Prevention" [2]. For. PowerGen steam turbines, about 59% of the total loss value and. 62% of loss events were. Precracking. ➢ The maximum stress in this work was no greater than 145 MPa. ➢The reversed plastic zone produced by precracking is about 2.5 µm. ➢ The specimens after producing precrack was stress relieved. ➢ For testing in air, the initial defect was produced using a sharp blade with diamond paste. After 10 years of operation of a steam turbine with large output power there was an accident during the turbine run-up. One of rotating blade fell off. All 6 LP rotors (two machines) were checked and many cracks on the L-1 blades were found. Due to economic reasons, blades with an identical geometry were manufactured. This paper presents a case study dealing with the assessment of cracking observed at steam turbine blade attachment holes, and subsequent use of an innovative repair solution based on a friction processing technique, friction hydro-pillar processing (FHPP). This was performed with a bespoke welding platform developed. ABSTRACT A prerequisite for the introduction of a new high strength steel blade in steam turbines is to ensure that its stress corrosion and corrosion fatigue performance is at least no worse than that of existing materials. To that end a series of. Commission of the European Communities. COST. Stress corrosion cracking and corrosion fatigue of steam-turbine rotor and blade materials. M. O. Speidel,1 J. Denk,2 B. Scarlin2. 11nstitute of Metallurgy. CH-Eth, Zürich. 2 Asea Brown Boveri. CH-Baden. Edited by. J. B. Marriott. Commission of the European Communities. Turbines with new upgrading LP Turbines. This decision is presented with review of the various steam turbine problems as: -. SCC on turbine discs. - blades cracking. - erosion-corrosion with comparison of various maintenance options and efforts undertaken by the NE Krško to improve performance of the original low. The procedure for repair welding of cracked steam turbine blades made of martensitic stainless steels has been developed using the gas tungsten arc welding process. Weld repair procedures were developed using both ER316L austenitic stainless steel filler wire and E. Key Words Nickel chromium molybdenum steels, Rotor discs, Corrosion Stress-corrosion cracking Corrosion Chlorides Pitting (corrosion) Turbine blades, Corrosion Water chemistry Feedwater Steam turbines Alloys Nickel chromium molybdenum steels — A470 Class 4 Background Applications The steam turbine drives an. Inspection of turbine blades and vanes: body, fillet, and root. > crack detection in high/low pressure valve body and bolting threads. > Detection of (near-)surface cracks in turbine casings. > Inspection of rotor shaft, shaft groove, and steam inlet and outlet piping, especially areas with welds, bends, or attachment points. He, Binyan (2015) Fatigue crack growth behaviour in a shot peened low pressure steam turbine blade material University of Southampton, Engineering and the Environment, Doctoral Thesis , 272pp. Record type: Thesis (Doctoral). PDF Thesis_Binyan He-25089471.pdf - Other. Download (56MB). E. Plesiutschnig, R. Vallant, G. Stöfan, C. Sommitsch, M. Mayr, A. Marn, and F. Heitmeier (2015). Cracks on the Roots of Turbine Blades of the Low-Pressure Turbine in a Steam Power Plant. Practical Metallography: Vol. 52, No. 4, pp. 214-225. https://doi.org/10.3139/147.110318. Corrosion fatigue crack propagation rates have been determined for two steam turbine blade steels, PH13-8, a candidate steel for advanced turbines and FV566, typical of current turbine blades. The testing was undertaken in simulated condensate environment, 300 ppb Cl- and 300 ppb SO42-, at 90 °C using trapezoidal. A root-cracked blade in a high-pressure steam turbine of a nuclear power plant had to be replaced with a new blade by cutting the shroud to remove the cracked blade. This necessitated in situ welding... Introduction. In low-pressure steam turbines, the steam cools down during its adiabatic expansion and a complex mixture of vapour and liquid phases is present [1]. The first (early) condensate can cause significant corrosion damage to the steam turbines, including stress-corrosion cracking. (SCC) of rotors, discs and blades. Some case histories of repair welding of steam generator components are discussed with special emphasis on details of repair welding of cracked steam turbine blades and shrouds in some of the commercial nuclear power plants using procedures developed. Keywords. Repair welding; steam turbine components; repair. Finite element method (FEM) is used to determine critical location, zone of the stress concentration at low pressure steam turbine disc, in which rotor blades are connected with rotation disc. At critical location of rotation disc initial crack lengths are assumed. For various crack lengths at LP steam turbine disc. steel steam turbine blade characterized via scanning auger. (NaCl + Na2SO4) solution, of steam turbine blades, made of martensitic stainless steel (12%. However, crack initiations within the bulk, from nonmetallic inclusions, have also been identified after 40000 h service, suggesting that the microstructure has evolved. Shukla A and Harsha S P 2015 An experimental and FEM modal analysis of cracked and normal Steam Turbine Blade Materials Today: Proceedings 2 2056-2063. Crossref. [4]. Jolanta B 2016 Redesign of steam turbine rotor blades and rotor packages-Environmental analysis within systematic eco-design approach Energy. forces related to the steam mass flow [6]. Furthermore, corrosion, causing crack initiation and propagation, is an significant failure mechanism in blades. This causes blades to be replaced or repaired and even probable re-design of elements [7]. In order to design a highly efficient steam turbine, it is essential to consider. Stress corrosion cracking of CrNi martensitic stainless steels for steam turbine blades. C.L. Verona* and R.L. Higginson. Department of Materials, Loughborough University, Loughborough,. Leicestershire LE11 3TU, UK. *E-mail: C.L.Verona@lboro.ac.uk. ABSTRACT. Stress corrosion cracking (SCC) is a delayed failure. Diagnostics of shroud ties of steam turbine blade system. Reliability of blades. The testing results of the shroud strip: 1- the field Нр distribution along the outlet edge of the shroud strip; 2 - the blade with detected crack; 3 - SC lines stipulated by jamming of shroud strips in U-shaped joints. Fig.2 presents the example of the. fatigue test facilities for LP steam turbine end stage blades at. Siemens and the successful execution of component tests with focus on High-Cycle Fatigue (HCF) regime. Results for blades of different sizes, surface conditions and materials have been evaluated. In addition, crack growth and threshold behaviour of blades. The present paper deals with the low cycle fatigue analysis of the low pressure (LP) steam turbine blade.. the centrifugal force because of the repeated startups of the turbine. The goal of the research is to develop a technique to assess fatigue life of the blade and to determine the number of startups to the crack initiation. such a straddle root disc with an indication of its crack locations and an example of catastrophic failure of a T-root blade attachment system. Fig. 2. a) Failure of T-Root due to non-detected cracking b) Steam turbine Straddle-Root discs with and without blades. Note the notch in the unbladed disc where the blades are. This tutorial paper discusses the basics of corrosion, steam and deposit chemistry, and turbine and steam cycle design and operation—as they relate to steam turbine problems and problem solutions. Major steam turbine problems, such as stress corrosion cracking of rotors and discs, corrosion fatigue of blades, pitting,. In 2006, Siemens Energy (then Siemens Power Generation Inc) issued an urgent technical advisory to recommend precautionary inspections of a certain class of two-flow steam turbines considered susceptible to blade root cracks in the L-0 row. The action was prompted by the 2005 separation of an L-0. aleeminku@kaeri.re.kr, bkhkim1700@kaeri.re.kr, ckhkim@kaeri.re.kr, dsm77@kaeri.re.kr, ewwkim@kaeri.re.kr, fhongsj@kaeri.re.kr, gckrhee@kaeri.re.kr. Keywords: flame hardening, 12cr steel, steam turbine blade, residual stress, martensitic transformation, crack formation. Abstract. This paper reports on the formation of. The focus on waste elimination has improved steam turbine blade machining and overall repair cycles immensely. Standard machining cycle times have been slashed with the transition from batch and que machining strategies to single piece flow for steam turbine blades. This transition has reduced cycle. Find out more on how we support and assist our customers with advanced engineering, production and quality expertise in steam turbine blades and components, with over eighty years of experience. Sulzer received a 55 MW geothermal steam turbine rotor from a customer in the Philippines for repair. The design is a double flow steam turbine type with 5 stages on each side. The rotor was received with stage 3 and stage 4 at the tur- bine side in un-bladed condition. The rotor was reported to have suffered blade failures. It is well understood that a crack presence in a turbine blade will alter its natural frequency and a cracked blade may thus experience resonance conditions even at... [29], Randall, R. L. and Rocketdyne, “Acoustic emission monitoring of steam turbines: final report," in Proceedings of the Joint ASME/IEEE Power Generation. Abstract: When a steam turbine was put out of service, cracks were noticed on many of the blades in the low pressure section round the stabilization bolts and perpendicular to the blade axis. The blades were made from chrome alloy steel X20Cr13 (material no. 1.402). When the bolts were brazed into the blades. During power plant shutdown and layup modes, steam turbines are exposed to oxygen, and the resulting corrosion can form tiny pits on turbine blades at random locations. Over years of operation, these pits can act as initiation sites for cracks that can destroy one or more blades or even entire turbines. 5/24/15. May 24, 2014: Loss of auxiliary power caused loss of cooling water and condenser back pressure increased during steam turbine trip. This event likely started a crack (or multiple cracks) at erosion pit areas on L-0 blade(s) that were then left dormant with normal back pressure limits and stresses. In April 2009, the steam turbine was overhauled again. No crack was detected. The analysis of the data allowed drawing some conclusions. The steam turbine. to the possible shaft crack. The Non-. Destructive Tests have been done only on accessible places not under the rotor blades. No shaft crack has been detected. The most endangered areas of rotor blades are upper parts of root where steam has acces. As a result of analisys [2] it was found that causes of failures originate in poor quality of steam. A conclusion from analysis [5] is that the direct reason of rotor blades cracking initiation is stress corrosion caused by simultaneous action. corrosion cracking in turbine blades, blade roots and blade attachment areas. Due to these facts, advanced non-destructive examination methods are required to ensure the safety and availability of the unit. 2. In- Service Inspection of Steam Turbine Blade Roots. The task faced here was to develop an. Abstract: Stress corrosion cracking of a 14 wt% Cr martensitic stainless steel, with commercial names PH-15Cr5Ni, FV520B or X4CrNiCuMo15-5, used for the manufacture of low pressure turbine blades, has been studied with the intention of gaining a better understanding of the processes involved, how they occur and why. Crack of a first stage blade in a steam turbine. (in lingua inglese) As mentioned before, for the single T root blade, the highest stress concentration was at the tang. The tang kept the blade coming out of the rotor disc when the centrifugal force was applied and hence when the tang was broken, the root rim was not tightly. lengths resulting in increased stress levels and allowing for a multitude of possible resonances. Various instances of low pressure steam turbine blade failures have been reported in [4-7]. Currently within the power generation industry in South Africa, fatigue cracking and failure of turbine blades is a predicament that faces a. Cracked turbine blades from a 600 megawatt steam turbine were submitted to Metallurgical Associates for analysis by an electric power utility. The main turbine steam pressure is 2400 psi at 1000 F° but only 250 F° at crack locations in the blade roots at the attachment to the hub. The unit had been subjected to 300. This Keynote paper discusses several vibration problems of steam turbine blades where the solution in each. further series of experiments on first stage blades in a turbine operating under high temperature steam inlet.. Recurring cracking of buttstrap connections, shown in Figure 9, between the 12 and 13 blade groups. Distortion of steam passages alters steam velocities and pressure drops, reducing the capacity and efficiency of the turbine. Where conditions are severe, deposits can cause excessive rotor thrust. Uneven deposition can unbalance the turbine rotor, causing vibration problems. As deposits accumulate on turbine blades,. The main goal of EC inspection automation was to develop a scanner-assisted method to inspect blade root cracking on L-2 stage of Westinghouse steam turbine. The scanner was designed to run on the extruded part of disk rim of Westinghouse steam turbine L-2 stage as its rail, and use L-1 stage disk rim as its supporting. In praxis, the entire HCF consists the life up to the crack initiation because the initiated crack propagates usually very fast in. d) mean centrifugal stresses in the steam turbine blade (Szwedowicz et al, 2006) and.. Campbell diagrams are presented for the last stage of steam turbine blades coupled by frictional bolts (Figure. The accumulation of damage caused by localized corrosion, pitting, stress corrosion cracking, and corrosion fatigue in low-pressure steam turbine components such as blades, discs, and rotors has been consistently identified as the main cause of turbine failure. The development of effective localized corrosion inhibitors is. Severe damage to the steam turbine. The inspection showed that the coupling had absorbed most of the vibrations when the breakdown occurred. This left the gearbox and generator relatively undamaged. However, the steam turbine was severely damaged: Diaphragms. Cracked welds; Bent vanes.
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