American-Eurasian Journal of Scientific Research 8 (5): 214-224, 2013ISSN 1818-6785© IDOSI Publications, 2013DOI: 10.5829/idosi.aejsr.2013.8.5.1126

Corresponding Author: Omid Ali Zargar, Department of Mechanical Engineering, Jawaharlal Nehru Technological UniversityHyderabad Kukatpally, Hyderabad-500085 Andra Pradesh, India.

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Vibration Analysis of Alstom Typhoon Gas Turbine Power Plant Utility

Omid Ali Zargar

Department of Mechanical Engineering, Jawaharlal Nehru Technological UniversityHyderabad Kukatpally, Hyderabad-500085 Andra Pradesh, India

Abstract: Vibration analysis consider as one of the most important parameter in preventive maintenance.Gas turbine vibration analysis also consider as a most challenging category in most critical equipmentmonitoring systems in this paper first I tried to introduce vibration analysis for different type of equipment usedin different industries. Then I will explain the most important tools and hypothesis used and analyzed for thesekinds of activities through a real case history. The people who are not directly involve in this matters hope tohave better understanding of most critical equipment vibration analysis and also I hope that the people whoare directly work in preventive maintenance can touch with different aspect of gas turbine vibration analysismethodologies as well as possible.

Key words: Vibration analysis Gas turbine Time wave form (TWF) Fast Fourier transform (FFT) Phaseangle Orbit Overall vibration Bearing clearance Unbalance Signal DecompositionTechnique Bently Nevada panel

INTRODUCTION connected to a data collector or analyzer the best points

Different maintenance strategies such as corrective process, that all of mechanical load of machine transfer tomaintenance, timebased, preventive maintenance, these parts. Also data collectors ability and software’scondition-based maintenance and predictive maintenance developed too much in recent years.for different equipment developed in recent years. Figure 2 shows some typical data collector use inHuman being speaks in different languages. When there condition monitoring systems spectra pro is relatedis some sickness they could speak to the doctors and talk software for easy viber and XMS is related software forabout the pains and discomfort but what is the machine vibro 60. time wave form (TWF) is the amplitude –timelanguage? Vibration is the machine language. The faults graph, fast Fourier transform (FFT) will draw by relatedof machines like misalignment, unbalance, soft foot, software’s and condition monitoring techniques bothbearing damage, high low and so on related to different FFT and TWF consider as main graphs in conditionparts of machine and each part have a unique frequency. monitoring systems.Vibration analyst is a kind of translator of machine To achieve better understanding in both FFT andlanguage in predictive maintenance. Some faults like TWF I explain some examples. Imagine we have a rotormisalignment, high low and soft foot consider as mother with small unbalance on the shaft and suppose that thisof others like bearing or gear damage and rotor touch. machine have not any other faults or problems.By translating this language we can predict these kind of Now imagine this machine have a cooling fan forhigh cost maintenance. Predictive maintenance developed bearings or an impeller.in recent years because of such economic considerations The frequency increase to 4X if X is equal to the[1]. In this part I try to introduce basic principal of rotational frequency of shaft in Figure 1. Now just imaginevibration analysis. Data processing procedure base on that this machine have a gear coupling and the gears havemeasuring the vibration of machine with a transducer 12 teeth.

for this purpose is bearings base on machine design

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Fig. 1: Measuring machine vibration by transducer anddata collector

Fig. 2: Typical data collector with their side facilities likepiezoelectric transducers. up easy viber and downvibro 60

Fig. 3: TWF and FFT Fig. 7: Typical machine different parts frequencies

The frequency increase to 12 X if X is equal to the In real industrial applications machines usuallyrotational frequency of shaft in Figure 1. Now just imagine consist of several different parts, each parts have athat we have all these part in a machine together. unique frequency thus we have usually complex TWF.

Fig. 4: Shematic of typical unbalance shaft rotating TWF

Fig. 5: Blade pass frequency 4X

Fig. 6: Gear mesh frequency 12 X

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Fig. 8: Complex TWF

Fig. 9: Schematic of a typicalTWF and FFT

Fig. 10: Unbalance(rotor) 1X, gear mesh 12 X and blade the sensitiveness of the coefficient response with respectpass frequency 4X to the changes of amplitude in TSA and frequency in

But how we can decompose these kind of complex Consider a typical dynamic signal as illustrated inTWF in real application, if you remember the Fourier Figure 11. The decomposition of the signal in the timetransform in mathematical engineering this will the key domain was done by considering the 2 order of theconcept for these purpose in different data collectors and Daubechies concept in signal decomposition process [2].related software’s that help us to separates individual The software’s have some facilities like cursor thatfrequencies and then detects how much vibration exist at can calculate these frequency accurately and compareeach frequency. them with the previous FFT condition of the machine each

Now just come back to our machine that have 3 basic part have a unique frequency and by monitoring thesefrequency thus this machine have theses all frequencies frequencies we can achieve the condition of each machinein its FFT then by monitoring these frequencies amplitude component separately and accurately.

we can monitoring the condition of gear shaft unbalanceand impeller separately.

Optimized Integrated Kurtosis-based Algorithm forZ-filter (I-kazTM) Coefficient using multilevel signaldecomposition technique developed in recent years TheI-kazTM coefficient (Z ) was originally developed base onthe 2 order of Daubechies signal decomposition.nd

Higher order of I-kazTM coefficients, 3 order (3Z ), 4rd th

order (4Z), 5 order (5Z), 6 order (6Z) and 7 order (7Z)th th th

were investigated by analyzing their response using twotypes of synthetic signals, TSA and TSB. The optimizedorder of I-kaz Multi Level coefficient was chosen base on

TSB synthetic signals. To simplifying the process

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Fig. 11: The decomposition process of a signal in I-kazprocedure

Fig. 12: General fault diagnosis typical diagram.

Trend of overall frequencies and vibration spectrum correctely. 2x also may related to misalignment or softprovide useful information to analyze defects in roller foot, 3x amplified by mechanical or rotary looseness’s.bearings. Trend indicates severity of vibration in High frequencies vibrations also may cause by some geardefective bearings. Vibration domain spectrum identifies or bearing problems (between 1000 to 20000 Hz) theseamplitudes corresponding to defect frequencies and diagrams just introduce general view to achieve betterenables to predict presence of defects on inner race and understanding of vibration analysis in machine faultouter race of roller bearings. The distinct and different diagnosis in real application professional software’s helpbehavior of vibration signals from bearings with inner race us to analyze the machine vibration with FFT and otherdefect and outer race defect helps in identifying the types of machine vibration graphs and also monitoringdefects in roller bearings. several frequency exist in ball techniques there are also some global standard for overallbearings inner race, outer race, cage, ball rotational and vibration alert and danger limits for different type ofball travel frequency can all detected by software in FFT equipment usually base on machine KW and also typesby adding the bearing code number and types to the of machine foundation like rigid and flexible foundationssoftware for each point in initial monitoring situation. The beside this vibration history of machine play a big role tosoftware will calculate all frequencies automatically [3]. such vibration limits definition in all fields in preventive

1X generally related to faults like unbalance, bent maintenance nowadays data collector software’s haveshaft, misalignment and soft foot because these faults different types of facilities that can help us to monitoringamplify by main rotational shaft speed the phase analysis special band frequencies in FFT for any further faultmay help us to distinguish the different characteristics of diagnosis applications [4].

Fig. 13: Bearing Fault Frequencies

Fig. 14: Frequency band trending with alarm and dangerconditions [5]

these faults and help us to diagnose the machine fault

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Experimental Detail: Alstom typhoon gas turbine is a critical equipment like rub, looseness and sleeve bearingkind of utility in our plant. And have an important role in problems. For time waveform analysis it is recommendedprocess. Therefore it is a kind of most critical that 1600 lines (4096 samples are used). This ensures thatequipment.TWF, orbit and phase analysis all are the data collected has sufficient accuracy and key eventsimportant factors in gas turbine vibration analysis beside are captured. Here are some academic TWF samplesFFT. In this part I will try to explain the vibration usually useful in most critical equipment.monitoring system of this gas turbine and also I will There are three condition that must be presentedexplain all key important elements in gas turbine vibration simultaneously to represented unbalance rotor firstanalysis mentioned before the gas turbine equipped with TWF should be have sine form and FFT must be mostlybently Nevada on line monitoring system the system in 1X then all direction overall vibration should be highbased on non-contact probe who monitoring the shaft beside this 90 shift phase between horizontal and verticalvibration usually in micrometer peak to peak. The overall or bently Nevada direction should be presented.vibration have some limitation standard for each High frequency TWF can represented roller bearingequipment that adjust for alert and danger condition in fair or gear faults in centrifugal pumps or gearbox equipmentcondition (passing the alert limit)the alarm lamp will but in most critical equipment it should be due to someindicate close monitoring condition and by passing process abnormality impact in compressor.danger limit the gas turbine will trip to prevent harmful Classical MW shape TWF can representeddamages in machine the bently Nevada main board misalignment in any industrial equipment. typical TWFequipped with some bently Nevada connections for that can representing rotor rub illustrated in Figure 21.mentioned data collector like easy viber that help us Beats & Modulation effects can representing somemonitor FFT, TWF and phase values the system also process problem mixed with some ordinary or abnormalequipped with overall vibration monitoring in process mechanical frequency and it is usually hard to diagnosissystem beside process conditions like inlet and outlet in most critical equipment.pressures and temperatures. Random impacts can representing in TWF and related

Wireless condition monitoring system developed in FFT and usually caused by some process abnormality inrecent years for most critical equipment like gas turbine gas turbines and other most critical equipment [10].the advantages of these kind of systems is reduce the The orbit is combination of two TWF in differentspecial tools installation errors as well as possible also the direction usually two main bently Nevada direction inaccuracy and speed of these kind of monitoring system is most critical equipment and can represented the motion ofmuch better than conventional portable systems the shaft in such equipment like gas turbines.that’s why orbitdisadvantages of these kind of systems is high cost of analysis can help us a lot in such equipment vibrationthem. [6, 7, 8, 9] Nowadays TWF vibration analysis plays analysis. Specially when we have a good bank of TWFa big role in preventive maintenance specially in most data and can obtain previous history of shaft orbits andcritical equipment like gas turbines. Now I try to explain compare them with new machine condition. Phasebasic principal of TWF vibration analysis. The time wave analysis is one of the other key factors in distinguishingform analysis usually complex in industrial equipment real faults of machine. it help us by trigger (usually) 1Xbut sometimes have some simple academic shapes that frequency TWF by a key phase and related reflectorcould easily represented some main faults in machine system on main shafts. In none critical equipment it canotherwise we should compare these kind of graphs with help us a lot to distinguish between the 1X faults in FFTmachine history and compare the changes accurately by like unbalance, soft foot, bent shaft and misalignment.different cursors and facilities in nowadays software’s. Beside this it is the key factor to diagnosis the high lowthere is some limitation in FFT analysis in such cases flange and also mechanical looseness. In most criticalTWF analysis will help a lot. The TWF analysis should equipment phase analysis is a key element specially inbe effective in some fields like, Low speed applications run up, coast down and bode diagrams that all base on(less than 100 RPM), Indication of true amplitude in phase elements and help us a lot to realizing the gassituations where impacts occur such as assessment of turbine or any other most critical equipment condition.rolling element bearing defect severity, gears, sleeve These kind of techniques will help us in some complexbearing machines with X-Y probes (2 channel orbit fault diagnosis process like shaft crack in most criticalanalysis), looseness, rubs and beats.as we can see lots of equipment. Unbalance considering as one of major faultsthese faults usually occur in gas turbines and other most that may occur in different rotary part of machine like main

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Fig. 15: Typical board monitoring system

Fig. 16: Typical none contact probe and its positions

Fig. 17: Bently Nevada connection board 3500 series machinery monitoring system

rotor or coupling the coupling unbalance is more difficult activities [12] having optimum understanding ofto diagnosis because of interfering the misalignment process parameter trend of all most critical equipmentcharacteristic with unbalance characteristic both in TWF always play an important role in vibration analysis.and FFT. The phase analysis could help us a lot in these nowadays many methods developed in modelingkind of condition to distinguish between these two main processing condition of such equipment. systematiccoupling faults. [11] shaft crack also consider as one of analysis of two-stage, axial flow turbine by using ofimportant faults in all most critical equipment and also gas different losses models and a new suggested algorithmturbines. This fault is usually hard to diagnosis. Shaft based on one-dimensional simulation. The suggestedcrack may be longitudinal or radial and it may have some method is found to be effective, fast and stable, inmicroscopic dimensions. The none contact probe may obtaining performance characteristics of multi-stagedetect wrong or fake data, alert, trip, TWF and orbit axial flow turbines. In one-dimensional modeling, massbecause of these kind of microscopic crack. These kind of flow rate, pressure ratio and efficiency are unknown,crack will disappear by metal spray in maintenance with define turbine geometry, inlet total pressure and

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Fig. 18: Unbalance rotor TWF

Fig. 19: High frequency TWF

Fig. 20: Calssical misalignment TWF

Fig. 21: Typical classic rotor rub TWF

Fig. 22: Typical classic Beats & Modulation effects in TWF

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Fig. 23: Typical classic random impacts FFT and TWF

temperature the turbine performance characteristics can related soft wares developed for vibration modal analysisbe modeled. This modeling is based on common that could help us a lot in foundation problem diagnosisthermodynamics and aerodynamics principles in a mean (like VDAU-6000 condition monitoring system). Thestream line analysis under steady state condition [13]. foundation design techniques also developed too muchMany vibration environments are not related to a specific in recent years. Damping is a complex phenomenondriving frequency and may have input from multiple which acts in the form of absorption and dissipation ofsources which may not be harmonically related. Examples the energy in the vibrational systems. Different factorsmay be excited from turbulent flow as in air flow over a effect on the damping such as type of joints in thewing or past a car body, or acoustic input from jet engine connections. Also more effective and efficient shockexhaust, wheels running over a road, etc. With these absorber designed in recent years that reduce the machinetypes of vibration, it may be more accurate, or interested vibrations specially in some critical location like airto analyze and tested using random vibration. Unlike cooling and cooling tower fans [15]. Also the effect ofsinusoidal vibration, acceleration, velocity and different machine and process parameter on the main rotordisplacement are not directly related by any specific or shaft natural frequency of all most critical equipmentfrequency. Of primary concern in random testing is the widely investigated in recent years and nowadays wecomplete spectral content of the vibration being have better understanding of such matter in mostmeasured or generated. Most random vibration testing critical equipment. Such fault diagnosis usually moreis conducted using Gaussian random suppositions for effective in startup and shut down machine trendboth measurement and specification purposes. With parameter. (Coast down and run up characteristics orGaussian assumptions, there is no definable maximum bode diagram) [16].amplitude and the amplitude levels are measured in RMS(root-mean-squared) values. On the other hand in low RESULT AND DISCUSSIONfrequency applications like reciprocating compressor datausually measured by peak to peak. The on line monitoring All gas turbines utility system consist of five mainrod drop system also available for such most critical parts, basic gas turbine, air compressor, air preheater,equipment also vibration analysis could be extremely combustion chamber and generator. Inlet and outletuseful for mechanical part of electro motor or generators pressure and temperature consider as main critical processfault diagnosis. (like all kind of bearings or gear parameter in all gas turbine systems [17].couplings) [14]. The machine foundation condition is also In this part I will explain a case history related to aone of the basic principal in preventive maintenance as gas turbine Alstom typhoon in oil industries. All criticalwell as machine installation. There are two kind of process parameter trends was on the range of technicalmachine foundation, flexible and rigid. Type of foundation document of gas turbine and in normal condition andhave a direct role in vibration standard of machine. The overall vibration data on bently Nevada main boardSoft foot, mechanical looseness and foundation problem increased too much but not overflowing the vibrationcould diagnosed by phase analysis in preventive ranges. The arrow show the direction of this increasing inmaintenance. Nowadays some kind of data collector and bently Nevada panel at Sunday, July 8, 2012.

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Fig. 24: Gas turbine system

Fig. 25: Bently Nevada panel before vibration analysis process

Fig. 26: Regular periodic rubs in NDE driven unit bearings

Fig. 27: Rub in NDE driven unit bearings orbit

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Fig. 28: Drive end unit bearings TWF and FFT

Fig. 29: Balancing weights positions (dynamic balancing panel-panel 2)

Fig. 30: Bently Nevada panel after balancing process

The TWF and related orbit of NDE driven unit specially in unbalance point. The vibration conditionsbearings show that there are some rub in this point and it come back to previous status and the vibration analysisshould be analyzing the oil sample in this point. The oil was successful.analysis report confirm this phenomena. Thus we firststrongly recommended check the bearing clearances in CONCLUSIONthis point.

Also drive end unit bearings TWF and FFT In gas turbine vibration analysis we should haverepresenting the dynamic unbalance in this point good monitoring data bank like overall vibration, FFT,(comparative to previous TWF and FFT in this point). TWF, orbit and also phase values. By comparing the data

Also we recommended operate dynamic balance we can achieve the optimum recommendation in thisprocess after static balance. These kind of field balance matter. it is also important to have a suitableprocess consist of accurate try and error balancing understanding of process conditions like inlet and outletprocess and adding suitable balancing weights in correct pressure and temperatures to analysis some aspect ofdirections in panel 2. TWF behaviors also we should always connected to

After balancing process and check the bearing other condition monitoring groups in different parts ofclearances the overall vibration decrease considerably world and industries to updates ourselves with new

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patent and innovation in monitoring systems and also 8. Mueen Uddin, Asadullah Shah, Raed Alsaqour anddeveloped and optimized vibration monitoring and Jamshed Memon, 2013. Measuring Efficiency of Tieranalysis techniques and evaluations. Level Data Centers to Implement Green Energy

ACKNOWLEDGEMENTS Scientific Research, 15(2): 200-207.

It is with great pleasure and deep sense of gratitude, Dawood, 2012. Enhancing Surveillance and Securitythat I acknowledge the successful completion of this of Oil Pipelines Transportation Using Wirelesspaper. My profound thanks and deep sense of gratitude Sensor Network. Middle-East Journal of Scientificto my dear sister Elahe Ali zargar and my dear friend Vahid Research, 11: 1030-1033.Nazari for their guidance and encouragement which were 10. Dunton, T., 1999. An introduction to Time Waveinstrumental in the successful completion of this paper. Form analysis. Universal Technologies Inc, 210: 4-8.

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