Condition Monitoring and Vibrational Analysis of Shaft Through Experimental and FEA Approach

Transcription

1 ISSN Condition Monitoring and Vibrational Analysis of Shaft Through Experimental and FEA Approach #1 Prajakta M Patil, #2 Ashish U Gandigude 1 praj.patil91@gmail.com 2 ashish.gandigude@zealeducation.com #1 Department of Mechanical Engineering, Dnyanganga College of Engineering & Research, Pune-41,Maharashtra, India #2 Department of Mechanical Engineering, Dnyanganga College of Engineering & Research, Pune-41,Maharashtra, India ABSTRACT Condition Monitoring is an advanced and very useful tool of predictive maintenance techniques. There is a wide variety of condition monitoring techniques currently in use for the diagnosis and prediction of machinery faults, but little attention has been paid to the occurrence and detection of vibration of rotating equipments.vibrations are found almost everywhere in rotating shaft. Shaft vibrates due to unbalances, misalignments, imperfect bearings and the crack on the shaft. In this project, the setup of the rotating shaft is established and it s observation and monitoring is done during operations. Monitoring of rotating shaft is done by forming the cracked of 2 mm and 4 mm at the centre of the shaft.the vibrations of the shaft calibrated in terms of the frequency and amplitude with the help of FFT Analyser installed on the outer bearing. This gives the amplitude of vibration of the shaft during operations ( 2800 rpm ). The of the physical validation has been correlated with the finite element approach to ensure the circumstances due to crack are correct. ARTICLE INFO Article History Received :18 th November 2015 Received in revised form : 19 th November 2015 Accepted : 21 st November, 2015 Published online : 22 nd November 2015 eywords Amplitude, Condition monitoring, FFT analyser, FEA, Frequency. I. INTRODUCTION Condition monitoring is process of monitoring a parameter of condition in machinery. Out of various condition monitoring vibration analysis is used in general way for fault diagnosis of mechanical component Study of present condition monitoring techniques There are only seven main techniques of condition monitoring.they are: a. Visual monitoring b. Contaminant or debris monitoring c. Performance and behavior monitoring d. Corrosion monitoring thermograph e. Sound monitoring. e. Shock pulse monitoring. f. Vibration monitoring A Vibration Moinitoring Vibration monitoring is a well established method for determining the physical Movements of the machine or structure due to imbalance mounting an alignment this method can be obtained as simple.[3] Easy to use and understand or sophisticated real time analysis, vibration monitoring usually involves the attachment of a transducer to a machine to record its vibration level special equipments is also available for using the output from sensor to indicate nature vibration problem and even its precise cost. Shafts are components subjected to difficult operating conditions in high-performance rotating equipment such as compressors, steam and gas turbines, generators, pumps, and engines that are used in process and utility plants. Major characteristics of structures, which undergo change due to presence of crack, are: 2015, IERJ All Rights Reserved Page 1

2 The natural frequency. The amplitude response due to vibration Mode shape Type of material component. An important part of dynamic finite element analysis is model analysis. Computer modeling alone can not determine completely the dynamic behavior of structures, because certain structure properties such as damping and non rarity do not conform to traditional modeling treatment. There are also boundary condition uncertainties which modeling needs additional help to work. Substantial advances in experimental techniques have complemented modeling with the experimental determination of structural properties. A milestone of this endeavor is the advent of digital Fourier Transform analyzers. The experimental techniques are nurtured by the theory of modal analysis.the main intent of the proposed work is to analyse the frequencies generated in the rotating shaft due to its dynamic s state of motion. These large amplitude vibrations need to minimize to avoid the noise generated due to its frequencies. To have the Surety of the Experimental, The FEA approach is being used to correlate the. The proposed work is to get the frequency response curves for rotating shaft and Minimize the amplitude of its vibrations and detection of crack in rotating shaft. II. PROJECT SET UP Fig. 2 Motor Single Phase Induction Motor Motor rating 230 volt 8.4Amps 0.75 HP Motor speed=2880 RPM C.FFT Analyser Instrument which does time to frequency domain conversion of dynamic signals. These could be firmware based or PC based systems. The Fast Fourier Transform is an algorithm for computing the Discrete Fourier Transform (DFT). The breaking the complex signal in to various sinusoidal components is achieved by transforming signals from time domain to frequency domain B.Motor Specification Fig.1 Experimental set up. Fig. 3 FFT Analyser III. RESULTS and OBSERVATION. A.Shaft Without Crack 2015, IERJ All Rights Reserved Page 2

3 Fig.4 Amplitude comparison of Physical test and FEA Fig.7 Amplitude comparison of Physical test and FEA Fig.6 Harmonic response for without crack shaft The from the experimental validations shows that the shaft start vibrating with the large amplitude mm at the frequency Hz i.e. ( *60 = rpm ). The shaft vibrates vertically at almost same frequency ( i.e Hz ) and amplitude mm, what is being observed in the Physical test. There is only 2.41 % difference in the amplitude of vibrations of physical test and FEA approach. So we can say that the shaft start vibrating at + or 10 % of 22.5 Hz frequency. The natural frequency of the shaft is Hz which matches with the 1 st motor harmonic of the motor and the shaft starts vibrating. Fig.8 Harmonic response for 2mm crack shaft The from the experimental validations shows that the shaft start vibrating with the large amplitude mm at the frequency Hz i.e. ( 20.21*60 = rpm ). The shaft vibrates vertically at almost same frequency (i.e Hz) and amplitude mm, what is being observed in the Physical test.there is only 0.89 % difference in the amplitude of vibrations of physical test and FEA approach. So we can say that the shaft start vibrating at + or 10 % of Hz frequency. It is observed that, In the 2 mm cracked shaft amplitude of vibration is increased by % than the without cracked shaft. It is considerable amount of increased in the amplitude of vibration and is only because of 2 mm crack in the shaft. The natural frequency of the shaft is 21.6 Hz which matches with the 1 st motor harmonic of the motor and the shaft starts vibrating. C.Shaft With 4mm Crack B.Shaft With 2mm crack 2015, IERJ All Rights Reserved Page 3

4 Fig.9 Amplitude comparison of Physical test and FEA Fig.9 Harmonic response for 4mm crack shaft The from the experimental validations shows that the shaft start vibrating with the large amplitude mm at the frequency Hz i.e. ( 21.26*60 = rpm ). The shaft vibrates vertically at almost same frequency (i.e Hz) and amplitude 16.1 mm, what is being observed in the Physical test. There is only 1.40 % difference in the amplitude of vibrations of physical test and FEA approach. So we can say that the shaft start vibrating at + or 10 % of Hz frequency. It is observed that, In the 4 mm cracked shaft amplitude of vibration is increased by % than the without cracked shaft. It is considerable amount of increased in the amplitude of vibration and is only because of 4 mm crack in the shaft. The natural frequency of the shaft is 22.5 Hz which matches with the 1 st motor harmonic of the motor and the shaft starts vibrating. D. Comparison Between all Three Shafts It is observed from the below graph that the shaft without crack having more frequency than the shaft with crack but the amplitude of vibration of the shaft without crack is less than both the 2mm crack shaft and 4 mm crack shaft. The amplitude of vibration increased in the 2 mm shaft is by % and in 4 mm shaft is by %. SO, it is really considerable amount of increased in the amplitude of vibration. MOD ELS T withou t T with 2 mm T with 4 mm FREQ UEN CY ( EXP ERIM ENT AL ), HZ FRE QUE NCY ( FEA ), HZ AMP LITU DE ( EXP ERIM ENT AL ), mm AMP LITU DE ( FEA ), mm % INCREA SED in AMPLIT UDE THAN the T without, % IV CONCLUSION When the natural frequency of the shaft matches with the force frequency of some external mean ( In our case the external mean is motor ) then the shaft starts vibrating. Every shaft vibrates due to this phenomenon as each object has its natural frequency but the intension of this project work is to demonstrate the effect and circumstances in the system due to present of crack in the shaft. It has been observed from result table that, when the shaft has 2 mm crack then the amplitude of vibration is increased by % and if the shaft has 4 mm crack then the amplitude of vibration is increased by %. This is really the considerable amount of increase in amplitude of vibration of shaft. So, as the crack in the shaft increasing the amplitude of vibration is also increasing and it may be very hazardous and can take some one s life. So, before using such systems need to ensure about the plane shaft to avoid the circumstances due to presence of shaft. REFERENCES Fig.11 Comparison between all three shafts E. Result Table [1] S. Sendhil umar, M.Senthil umar Condition Monotiring of rotating machine through vibration analysis journel of scientific and industrial research vol 73 april2014 pp [2] G. Suresh Babu*, Dr. V. Chittaranjan Das condition monitoring and vibration analysis of boiler feed pump International Journal of Scientific and Research Publications, Volume 3, Issue 6, June ISSN [3] R..Biswas vibration based condition monitoring of rotating machines national conference on condition monitoring [NCCM-2006] December 2006 pg no , IERJ All Rights Reserved Page 4

5 [3] Linaraju. a paper on condition monitoring and vibration analysis of rotating equipment [NCCM-2006] December 2006 pg no [4] A.C. Babar1, A.A. Utpat2 Vibration Analysis of Misaligned Rotating Shaft IJMEIT//VOL-2//PAGE NO [5] Vaibhav J SuryawanshiȦ* Vibration Based Condition Assessment of Rotating cracked shaft using changes in critical speed and RMS Velocity response functions. International Journal of Current Engineering and Technology ISSN page no [6] Ali Vaziri, Prof. M. J. Patil Vibration Analysis of A Cracked Shaft Vaziri, International Journal of Advanced Engineering Technology E-ISSN [7] A. Tlaisi1, A. Akinturk1, A. S. J. Swamidas1 & M. R. Haddara1 Crack Detection in Shaft Using Lateral and Torsional Vibration Measurements and Analyses Published by Canadian Center of Science and Education Vol. 2, No. 2; 2012 page [8] F.P. Garcia Ma rquez, A.M. Tobias, J.M. Pinar Perez, M. Papaelias, Condition monitoring of wind turbines: techniques and methods, Renewable Energy 46 (2012) [9]Lee Y.S., Lee C.W., (1999): Modelling and analysis of misaligned rotor ball bearing systems, Journal of Sound and Vibration. [10] A.A. Mohamed Monitoring of Fatigue Crack Stages in a High Carbon Steel Rotating Shaft Using Vibration Published by Elsevier Ltd. Selection and peer-review under responsibility of ICM11Open access under. [11] G.I. Giannopoulos, S.. Georgantzinos, N.. Anifantis coupled vibration response of shaft with breathing crack Journal of Sound and Vibration, Volume 336, 3 February 2015, Pages [12] Y. Ishida, T. Inoue, Detection of a rotor crack using a harmonic excitation and nonlinear vibration analysis. [13] Jose M. Machorro-Lo pez Douglas E.Adams JulioC.Gomez-Mancilla b, amran A.Gul Identification of damaged shaft using active sensing Simulation and experimentation Journal of Sound and Vibration 327 (2009) , IERJ All Rights Reserved Page 5