Torsional sn curves, determined on smooth bars containing surface. A methodology for predicting torsional fatigue life of. Torsional loads on circular shafts interested in stresses and strains of circular shafts subjected to twisting couples or torques generator creates an equal and opposite torque t shaft transmits the torque to the generator turbine exerts torque t on the shaft. Lees the influence of cracks in rotating shafts jj.
Crack initiation and crack growth can lead under service conditions to damages on components and has been probably already influenced by operating or environmental conditions. A methodology for predicting torsional fatigue life of turbine generator shafts using crack initiation plus propagation responsibility prepared by general electric company, steam turbinegenerator engineering and manufacturing department. The naval bronze bushing was original to the unit and had exceeded its life expectancy. The interaction of the mutual fracture surfaces results in a pressure and a frictional. Methodology for predicting torsional fatigue life of. Reliable clamping of the insert has a great impact on the quality of the component. Shaft crack detection in a steam turbine isma past editions. The resonance frequencies of the shaft with the circumferential crack depend on the crack length and location. Motor shaft materials for most motor applications, hot rolled carbon steel is a good choice. Patil address for correspondence research scholar1, assistant professor2, bharati vidyapeeth university college of engineering, punesatara road, pune, mh, india abstract we know a shaft crack is a detection of such shaft crack is a very serious matter. The effect of crack surface morphology factory roof, pitch height and wave length on the effective stress intensity. A clutch enabled the steam turbine to be connected to the generator in onload. Bently nevada technical bulletin 270 early shaft crack.
The result was a huge torsional stress and a cracked shaft. The shaft is assembled from single sections cylinder, cone and polygon including features chamfers, fillets, neckdowns, and so on. Understanding the root causes of axial cracking in wind. Digital simulation transverse crack of a rotating shaft with a. The fatigue and fracture analysis of steam turbine rotor. Crack growth prediction of the steam turbine generator shaft.
Adequate assessment of steam turbine components is a key issue in life management of steam turbines. Mptab7i2007r 20 calculation of vbelt tensions and shaft loads mechanical power transmission association 5672 strand court, suite 2, naples, fl 34110. It can estimate previous torsional transient damage and predict residual life. Turbine and generator rotors and shafts undergo high stresses during regular working life and, from a. When higher loads are present, an alloyed steel such as chromiummolybenum crmo is frequently used, and for applications with extreme corrosion or hostile. Foreword this foreword is provided for informational purposes only and is not to be construed to be part of any technical specification. What is important is the performance of the product and our ability to create a robust product that fulfills the customers demands. Autocad mechanical provides a utility known as the shaft generator, which enables you to draw solid and hollow shafts.
Abstract turbine generator shafts are often subjected to a complex transient torsional loading. Mode iii crack growth in turbo generator shafts often results in a fracture surface morphology resembling a factory roof. Vibrationbased crack diagnosis in rotating shafts during. Crack rotor test rig the test set up comprised a 50hp37kw three phase electric motor connected to a 3 phase generator by means of a shaft 1450 mm long and 38 mm in diameter. It extends the system operating life, improves system availability and retains the system. Spider generator shafts offered can be made available by us in different finish specifications using material options like stainless steel, carbon steel and others with different surface treatment options like polishing, nickel plating, chrome plating and others.
Shaft and bearing calculations gulf states engineering. The power network in china is encountering great changes and largescale network is increasingly implemented for long distance power transmission as well as various kinds of power electronic devices, which bring in the risk of the torsional vibration of the turbine generator shafts, may cause the fatigue damage and cracks in the product life cycle. To plan for a repair, the seal of the bearing was moved up and the lower third of the bushing was removed. The customer reported that the generator rotor had suffered a collector ring failure and also a ground to the main shaft. The influence of cracks in rotating shafts journal of sound and vibration, volume 285, issues 45, 6 august 2005, pages 10151037 jj. Just some rectangles like so,and some lines to represent the shaft. The shaft is assembled from single sections cylinder, cone and polygon including features chamfers, fillets, neckdowns, and more. Learn how to add internal contours for shafts using the shaft generator tool in autocad mechanical 2016. Therefore, turbogenerators, aircraft engines, compressors, pumps, and many. Research paper vibration analysis of a cracked shaft 1ali vaziri, 2prof. Ger4212 ge generator rotor design, operational issues.
Coupled torsional vibration and fatigue damage of turbine. Root cause ac motor failure analysis with a focus on shaft. Research paper vibration analysis of a cracked shaft. Cracks in rotating shafts, in epri, 4th incipient failure detection conference, predictiv e maintenan ce for the 90s, philadelphia, p a, october 1517, 12 6. Modeling and calibration for crack detection in circular shafts.
Abstract to provide a basis for estimating fatigue life in large rotating generator shafts subjected to transient oscillations, a study is made of fatigue crack propagation in mode iii antiplane shear in torsionallyloaded spheroidized aisi4340 steel, and results compared to analogous behavior in mode i. Various researchers have studied the response of cracked shafts and the work on the diagnosis of cracks has. Major arcing and heat damage occurred to the generator rotor forging shaft. Now as you can see, weve got some very simple objects againin the autocad mechanical drawing. Also, extensive repair can cause residual stressing in the runner resulting in structural cracking at areas of high stress. But because the material is ductile, the angle of the crack it is not at the 45 position. General electric co a methodology for predicting torsional fatigue life of turbine generator shafts using crack initiation plus propagation. Here, we investigated the dynamic response of solid turbo generator shafts with longitudinal and circumferential cracks.
Many technical papers on axial cracking in the past couple of years have focused on why this unusual bearing phenomenon is so prevalent in wind turbine gearboxes. Highspeed reclosing system and machine considerations. Axial cracks on inner rings of high speed and intermediate speed bearings have become a leading cause of wind turbine gearbox life issues. The defects onin the rotor shafts were regularized by the method of. In short, this improved methodology allows utilities to. As part of service life analyses, highlystressed bolted joints have also been subjected to ultrasonic examination from inside the heat bore for some time now.
The effect of steady torsion on fatigue crack growth in shafts. In addition to lowering operational costs, increased efficiency often translates to fewer emissions and can mean better compliance with environmental legislation. Function of a generator rotor this section covers the generator fields function in two main areas. Variable frequency drive for shaft generator ptopti shaft generators are commonly used to produce electrical power for the ships network, in vessels.
The current trend among machinery users is to extend the life of rotating. Shaft crack detection method rem technologies, inc. The inability to detect a crack at earlier stages, can leave insufficient time to schedule the manpower, parts, etc. Another signalbased method for shaft crack detection has been. Such transient torques may initiate and propagate a circumferential crack in the shafts. Heavy roughing of large forgings, long, with uneven surfaces but stable conditions are followed by extensive finishing of bearing surfaces. Failure analysis of hydraulic turbine shaft request pdf. The shaft is connected to the motor and generator using fenner. Case study rotor spider cracking chelan county public utility district cpud of chelan.
Monitoring of fatigue crack stages in a high carbon steel rotating. Often the symptoms of a shaft crack propagation are masked by those of other usual. Damage mechanisms such as fatigue driven cracklike flaws could lead to sudden and potential catastrophic unit failure. This was necessitated by the failure of a turbine rotor at southern california edisons mohave station in 1970 and 1971. Lees2 department of mechanical engineering, university of wales swansea, singleton park, swansea sa2 8pp, wales, uk. Add cylindrical or conical sections add features such as center holes, chamfers, grooves, fillets, threads, profiles and wrench fittings add standard parts such as bearings, gears, retaining rings and seals the shaft. Perform a strength check and generate the shaft into the autodesk inventor. Different faults such as shaft cracks, bearing failures, rotor. Vaziri and hashemi 67 in a series of investigations studied dynamic response of shafts with circumferential crack considering complexity of the cracked surface. Shaft deflection, runout, vibration, and axial motion. The objective of the present study is to evaluate the vibrational characteristics of turbogenerator shafts with a circumferential crack of various lengths by taking into account the local energy loss in the crack region due to the plasticity at the crack tip and the frictional energy loss due to the crack surface interactions. A crack may propagate from some small imperfections on the surface of the body or inside of the material and it is most likely to appear in correspondence of high stress concentration. In the lefthand side of figure 3, the sleeve is eggshaped, as may happen with thin, large diameter sleeves. In this study, the assessment and calculation methods for the crack propagation life of steam turbine rotor shafts containing defects are presented.
Instructor another fantastic mechanical part generatoris the shaft generator in autocad mechanical. The effective torsional rigidity was found to be a function of ratio of crack depth to the shaft radius only. Man primeserv onsite recovery has many years of experience in machining generator shafts, both on onshore and offshore wind turbines worldwide. A critical need thus exists for a reliable, easy to implement shaft crack detection method which can identify the presence, size, and location of a shaft crack in the early stages of crack development. That, unfortunately, has led to many motor and driven shaft failures due to torsionalfatigue factors. Variable frequency drive for shaft generator ptopti. Generator rotors, shafts and turbine runners typically come to mind when considering critical rotating equipment in a hydropower station. The effect of crack surface interaction on the stress. Variational formulation of a rod under torsional vibration. Fonte and freitas 2008 has taken a case of marine engine crankshaft failure which was similar to the diesel generator crankshaft studied by jimenez espadafor in which cracks are produced on the crankpin fillet due to bending and and elevation of crack appears to be semi elliptical in shape.
The interaction of the mutual fracture surfaces results in a pressure and a frictional stress field between fracture surfaces when the shaft is subjected to torsion. Mode iii fatigue crack propagation in low alloy steel. Use the shaft component generator to design the shape of a shaft, add and calculate loads and supports, and other calculation parameters. Method of shaft crack detection based on squared gain of vibration.
Crack detection in a rotating shaft using artificial. The analytic methods for estimating the average stress and the alternating stress amplitude of the steam turbine rotor shafts are introduced. Shaft crack, generator, finite element method, fault diagnosis. It was stated in that the dynamics of cracked rotors was first done by the general electric company. While the most common torsional fatigue cracks start at the sharp corner stress concentration at the bottom of the keyway when couplings are poorly fitted, another common appearance is the diagonal shaft crack like that shown in fig. The diagnosis of cracks in rotating shafts using nondestructive techniques. Depending on the severity of the disturbance, the amplitudes. So, youve dropped your keys down the narrow crack where the doors open in an elevator. The paper analyzed the failed coupling of some 600mw steam turbine generator and calculated the. Consequently, it is impossible to analyze all combinations of impellerspropellers, volutes, drive units and running conditions. Crack failures continually occur in shafts of turbine generator, where grid disturbance is an important cause. Turbo generators shafts are manufactured through the extrusion process. The development of crack detection methods in rotating shafts was initiated at about 1970. To estimate influences of grid disturbance, coupled torsional vibration and fatigue damage of turbine generator shafts are analyzed in this work, with a case study in a 600mw steam unit in china.
Crack detection in a rotating shaft using artificial neural. We specialise in executing shaft repairs uptower, thereby minimising expensive downtime for operators. Failure analysis of machine shafts efficient plant. Machine train consists of steam turbine 63 mw, generator 177 mw and gas turbine 114 mw. The longitudinal cracked section of the shaft section was modeled as a shaft with reduced effective torsional rigidity.
Generator shaft spider generator shafts manufacturer. Generator shaft there is a range of typical turning operations used for shafts that have undergone real continuous improvements. The effects of longitudinal and circumferential cracks on. Vibrationbased crack diagnosis in rotating shafts during acceleration through resonance jerzy t. Dorfman and trubelja 12 used a simplified model of the turbine generator system to examine the influence of cracks in the shaft. An overall methodology now exists that addresses both crack initiation and propagation in predicting the fatigue life of large turbine generator shafts.
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