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Research ArticleResearch into Correlation between the
Lubrication Mode ofContact Surfaces and Dynamic Parameters
ofTurbo-Generator Transmissions
Marek Kočiško , Petr Baron , Monika Telı́šková , Jozef
Török , and Anna Bašistová
Faculty of Manufacturing Technologies with a Seat in Presov,
Technical University of Košice, Košice, Slovakia
Correspondence should be addressed to Petr Baron;
[email protected]
Received 6 March 2019; Revised 15 July 2019; Accepted 9
September 2019; Published 9 October 2019
Academic Editor: Stanislaw Dymek
Copyright © 2019MarekKočiško et al.-is is an open access
article distributed under the Creative CommonsAttribution
License,which permits unrestricted use, distribution, and
reproduction in any medium, provided the original work is properly
cited.
-e paper presents the results of an experimental study aimed at
assessing the correlation between the measurement of
dynamicparameters (vibration, high-frequency vibration, and
acoustic emission) and the analysis of friction mode and the state
oflubrication of the contact surfaces of two gearboxes in the
turbo-generator assembly (high-speed single-body steam
turbi-ne—gearbox—generator) with the transmission power of no more
than 50MW. -e analysis confirmed the assumption of asignificant
correlation of the monitored high-frequency vibration signal with
the unsatisfactory engagement of the gear teeth.-rough vibration
analysis, an increased level of the tooth vibration component and
vibration multiples with increased acousticemission were identified
in gearbox operation.-e gear oil of one of the gearboxes examined
showed a loss of additive elements inthe real operation of the
contact surfaces of the teeth engagement. -e trend analysis
confirmed the complexity of the monitoredtransmission operation in
terms of the friction mode and the influence of the oil quality on
the state of the toothflank microgeometry.
1. Introduction
Nowadays, industries are based on a wide use of machineryand
enginery without which production would not bepossible. -erefore,
the demands on production, growth,and quality, which are very
closely related to the demands onthe reliability of the production
equipment, are constantlybeing laid down. Regular inspection of the
technical con-dition and early diagnostics of an error in many
cases lead tothe early detection of a malfunction that could cause
con-siderable damage during operation. Technical diagnostics isof
major importance for the operation and maintenance ofequipment [1].
It is a subject of wide interest not only in thescientific field
but also in the field of application of its resultsin the area of
newly developed methods and their use inprofessional practice.
-e aim of monitoring the rotating machine vibration isto obtain
data about its technical condition.-e process dataobtained in this
way comprise an information base for
identification of faults and errors in the technical system
andconsequently the provision of timely repair or maintenance,in
order to extend the service life and reliability of
individualmachine parts and equipment as a whole. During its
op-eration, the technical equipment generates vibrations which,on
the one hand, represent possible damage to the machinenode and also
reflects the real operating conditions of themachine. Vibrations
are considered to be the best operatingparameter by which
low-frequency dynamic states can beassessed, such as imbalance,
loss of alignment, mechanicalbacklash of the housing, overrun of
the stability of flexiblerotor systems, insufficiently rigid
foundations, bent shaft,excessive bearing wear, or the fact that a
rotor blade hasbroken loose [2]. -e basic principle of individual
methodsof vibrodiagnostics is based on the measurement of
thecharacteristic values of mechanical vibration and in
thesubsequent comparison of its results with the limit
valuesprescribed by technical standards and the manufacturer,
orused on the basis of long-term experience in monitoring the
HindawiAdvances in Materials Science and EngineeringVolume 2019,
Article ID 8148697, 10
pageshttps://doi.org/10.1155/2019/8148697
mailto:[email protected]://orcid.org/0000-0002-0935-4871https://orcid.org/0000-0002-4789-529Xhttps://orcid.org/0000-0003-1044-2665https://orcid.org/0000-0003-3652-7181https://creativecommons.org/licenses/by/4.0/https://doi.org/10.1155/2019/8148697
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technical condition of the equipment. Further evaluation ofthe
vibration signals is based mainly on the analysis of twocomponents,
namely, the amplitude and the frequency.Frequency spectrum is also
analyzed by the application ofmultiple methods and indicators such
as peak values, peak topeak, mean values, effective values (RMS),
time courses, fast-Fourier transform (FFT), envelope methods, and
trendinganalysis [3].
To determine the bearing lubrication condition, verifi-cation of
the gearing and lubrication condition in thegearboxes and vibration
acceleration measurements can besuccessfully applied to
appropriately selected frequencyranges.
2. Literature Review
Generally, the gears represent mechanisms used to transmitpower
through a rotating motion. -ere is a change in thetorque and speed
of the machine. Toothed mechanical gearsare tied gears that
transmit torque to short distances betweenthe drive and the driven
shaft.-ey work with high efficiencyand are quite stable over a
large speed range. -e gears are asignificant source of vibration in
the gearboxes. As a result ofthe load (engagement of the teeth),
the toothed gears roll offeach other and their contact is
accompanied by elastic de-formations. Consequently, deviations from
the theoreticaltooth profile itself can occur, resulting in a
transmissionerror and its subsequent excessive vibration. -e
emergenceof vibrations in gears can also be affected by so-called
pitting(occurs by shear and pressure acting on the flanks in
thetoothing, when various defects appear on the surface as aresult
of cyclic loading), bearing defects, shafts oscillation,and so on.
It is important to note that working condition ofgear system is
extremely complex. Typically, the primaryengine introduces an
external load; however, internal in-centives introduced by
time-varying meshing stiffness andgear error are the main source of
vibration in the trans-mission system. Lu et al. in their published
work [4] describethe novelty of the integral squeeze film damper
(ISFD),which is proposed to reduce the vibration excitation of
thegear system through the foundation. Four ISFD designs weretested
experimentally with an open first-grade spur gearsystem. Different
vibration amplitudes of gear shafts withISFD installed on driven or
driving shafts were compared.Results showing that vibration
reduction is better whenISFD is installed on the drive shaft than
on the driving shaft[4]. ISFD elastic damping support can
effectively reducetransmission of meshing excitation effectively.
No additionalchanges need to be made to the equipment and
foundationto achieve good vibration control [4]. Fargère and Velex
intheir scientific article “Some Experimental and SimulationResults
on the Dynamic Behavior of Spur andHelical GearedTransmissions with
Journal Bearings” describe research onthe interactions between
dynamic and tribological behaviorof gears [5]. A model is
introduced which incorporates mostof the possible interactions
between gears, shafts, and hy-drodynamic journal bearings. It
combines a specific elementfor wide-faced gears that includes
normal contact conditionsbetween actual mating teeth, that is, with
tooth shape
deviations and mounting errors, by journal bearings de-termined
by solving Reynolds’ equation [5]. -e authorscompared the results
of the simulation with the measureddata obtained on a
high-precision test equipment. -e au-thors present the model, which
is the global behavior of thesystem (shaft vibrations) and the
contacts between the gearteeth and those in the journal bearings.
Tooth micro-geometry including shape modifications and errors is
takeninto account, and the influence of temperature on
theproperties of the bearing lubricant is also considered. In
theirpaper “Feature Extraction Using Discrete Wavelet Trans-form
for Gear Fault Diagnosis of Wind Turbine Gearbox,”[5] Bajric et al.
characterize vibration diagnostics as one ofthe most common methods
for assessing the condition of awind turbine equipped with a
gearbox [6]. Due to thestochastic operation of wind turbines, the
gearbox shaftrotating speed changes with high percentage, which is
theapplication of traditional vibration signal processing
tech-niques, such as fast-Fourier transform [6]. -is workpresents a
new approach to high-speed wind turbine shaftsdiagnostics using
discrete wavelet transform and time-synchronous averaging [6]. One
of the most importantinsights to be drawn from this work is
choosing a suitablereference for a synchronous averaging and
condition in-dicator that can lead to the earlier diagnosis of wind
turbinehigh-speed shaft gear fault.
-e aim of the scientific paper by Barbieri et al. was toidentify
the presence of component errors in car trans-missions by comparing
the vibration signals of damaged andundamaged transmissions.
Different signal analysis tech-niques based on wavelet transform,
mathematical mor-phology, and energy (entropy) were used to verify
thepresence of damage in the systems [7]. A signal
processingtechnique combining pattern spectrum and selective
fil-tering in certain frequencies ranges was used for
identifi-cation of component failures [7].
An interesting sophisticated solution applied to theprocess of
identifying and classifying faults in transmissionsis the
implementation of the convolutional neural networkdeep learning
algorithm (CNN). It is a network of smallcomputing units, the
so-called neurons, that send processedinformation to each other
down a hierarchy. Chen et al. havepublished research results in
which various combinations offault conditions have been integrated
within the neuralnetwork. -e present CNN method identifies and
classifiesfaults in gearbox using vibration signals measured with
anaccelerometer. Feature representations are selected with theinput
parameters of the CNN with the vector formed byRMS values, standard
deviation, skewness, kurtosis, rotationfrequency, and applied load.
For the evaluation of theproposed CNN method, the gearbox fault
diagnosis ex-periments were carried out using different techniques.
-eresults show that the present method has outstandingperformance
of gearbox fault diagnosis, compared with peermethods [8].
Strączkiewicz and Barszcz their paper “Ap-plication of Artificial
Neural Network for Damage Detectionin the Planetary Gearbox of Wind
Turbine,” used the neuralnetwork to identify wind turbine
transmission failures. -esudden increase in the monitored signal
does not
2 Advances in Materials Science and Engineering
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automatically translate into an error. To overcome thisobstacle,
it is proposed to detect and fault with the artificialneural
network (ANN), and further observation of linearregression
parameters was calculated on the estimation errorbetween healthy
and unknown condition. -e proposedreasoning is presented on the
real-life example of a ring gearfault in a wind turbine’s planetary
gearbox [9].
In their publication, Myshkin and Marková discuss thetrends in
tribodiagnostics, the development of continuousmonitoring systems
and the increase in the number ofsensors in the oil line, software
development, includingartificial intelligence methods, and the
reduction of tribo-diagnosis costs [10]. It has been demonstrated
that the mostpromising direction in the performance of the oil
taking intoaccount the existing ambiguity, incompleteness, and
fuzzi-ness of information is the application of an expert
system[11]. In their publication, “Early Fault Diagnostics of
Bearingand Stator Faults of Single-Phase Induction Motor
UsingAcoustic Signals,” Glowacz et al. are concerned with
early-fault diagnostics based on acoustic signals for
single-phaseinduction motor. -e authors have measured and
analyzedthe conditions of single-phase induction motor and engineof
single-phase induction motor with wrong bearing [11].Determination
of the technical condition of axle housing in avehicle by means of
vibrodiagnostics is discussed in thepublication by Furch et al.,
who describe an experiment inwhich the vibrations of the axles
located in the vehicle axlehousing were measured, and the analysis
of the measureddata was then performed. Subsequently, they analyzed
thelubricant samples used for the lubrication of the testedrolling
element bearings [12]. Properly chosen technicaldiagnostics and
follow-up measures based on the knowledgeof the real condition of
the machinery are the main steps thatlead to its increased
operational ability. Repair costs are oftenoutweighed by
investments made in preventive mainte-nance, as discussed by Glos
in “Tribologic Methods Used forEngine Diagnostics” [13]. At
present, automated controlsystems and dilution are assured by
complex technical de-vices that include a large number of elements
and have acomplex structure. Automated system of management
oftechnical process (ASMTP) is a group of solutions ofhardware and
software designed for automation control oftechnological equipment
in industrial enterprises. -is re-search is addressed in [14].
Vibrations are a phenomenon accompanying the op-eration of
technical systems. Vibrations characteristics ofindividual devices
operation are unique to a particular de-vice. Connections between
the individual functional parts ofa technical equipment change
during operation. Bearingbacklash increases, weight of worn parts
changes, operatingparameters change [15]. -is causes a change in
machinevibration. -is change is the characteristic of the device
andoffers information about the states that occurred in themachine
structure.-us, vibration examination and analysismust be an
integral part of all activities ensuring optimaloperational
reliability.
Vibration-based monitoring techniques have been usedfor
detection and diagnosis of defects for several decades.-ese methods
have been traditionally applied, separately in
time and frequency domains. A time-domain analysis isbased on
statistical characteristics of vibration signal such aspeak level,
standard deviation, skewness, kurtosis, and crestfactor. A
frequency domain approach uses Fourier methodsto transform the
time-domain signal to the frequency do-main, where further analysis
is carried out, conventionallyusing vibration amplitude and power
spectra [15].
3. Measurement and Analysis of the TurboGenerators’ Operating
Conditions Based onTechnical Diagnostic Methods
Under the current conditions, the service life of the gear
unittoothing is 8 to 10 years. Toothing replacement
significantlyincreases maintenance costs, as the cost of toothing
re-placement is relatively high. -e most important faultsdetected
in the cogwheels are those due to fatigue. Contactfatigue damage is
characterized by accumulation of defectsin the surface layer of the
material if it is subject to excessivecyclic loading of the bodies
at their mutual contact point.Figure 1 is a demonstration of gear
toothing damage.
-e delivery date for a new gear assembly includingtoothing is 9
to 18 months. In the case of toothing damage, itis necessary to
carry out emergency repair and then dynamicrotor balancing. Once
repaired, it is possible to operate sucha machine at reduced power,
max. 50% of the nominalpower.
Figure 2 shows an example of emergency repair of thecogwheel by
welding, its reassembly, and commissioning,with a limitation of up
to 50% of the transmitted power.
3.1.!eResearch Issue. Following the request of our partner,we
conducted an analysis of the current state of the turbo-generator
gearbox. Our partner uses a three-phase, air-cooled synchronous
generator to produce electricity. -esteam turbine is connected to
the generator via a high-speedgearbox ensuring efficient and
high-efficiency transmissionof torque from the turbine shaft
through the clutch to thegenerator shaft. -e turbine and the
generator are mountedon a common frame fitted onto a simple
reinforced concreteblock, separated from the surrounding floor of
the machineroom to allow for dilatation. -e turbo-generator
gearboxreduces the speed of the turbine rotor. -e reason for
themeasurements and analyses was an increased noise level ofthe
gearbox. By analyzing the operating parameters, nodependence
relationship between the change in the gener-ated noise and the
performance, for example, has beendetected. -reefold and greater
increase in the noise wasrecorded from the levels of vibration
acceleration valuesthrough sensors that were placed on the
gearbox.
In our laboratory, measurements and subsequent ana-lyzes of
turbo generator were conducted focusing ontransmission of 50MW by
toothed gear. In order to de-termine the correlation between the
monitored dynamicparameters and the assessment of the friction mode
and thelubrication status for the gearbox, the analyzed chemical
andphysical properties of the oil filling of the examined
gearbox
Advances in Materials Science and Engineering 3
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were compared with the gearbox of the identical turbo-generator
system.
On the basis of diagnostics, the following tests andanalyzes
were performed:
(i) Vibrodiagnostics of the gear unit(ii) Dynamic signal
analysis(iii) Analysis of lubricating oils with emphasis on lu-
bricity test and load bearing capacity of oil film
-e gear unit was used for the transmission of power inthe
following turbo-generator assembly: high-speed single-stage steam
turbine—gear unit—generator. Such a machinedesign is mainly used in
heating plants with power outputsup to 50MW. -e basic conditions
for using such an as-sembly in terms of durability and reliability
of machineoperation include, in particular, the following:
(i) -e mechanical efficiency of the gear unit and theloss of
power transmission are particularly true inthe summer when the
machine is used for 50% (noheating period, and only hot water is
heated). -eoverall machine efficiency is less favorable in thistype
of operation.
(ii) Coaxial alignment of the complete set, bearing inmind that
the bearings are located in sliding hy-drodynamic
bearings—displacement of the pinaxis during operation and during
shutdown. At thesame time, the sprocket of the gearbox works dueto
the forces at the top of the bearing. It is necessaryto calculate
these displacements and correct thesetting in both the horizontal
and the verticaldirections.
(iii) Coaxial shaft alignment is also required whenconsidering
thermal expansion during opera-tions. It is recommended to
determine thetemperature ratios during operation and calcu-late the
correction based on the real conditions oftemperature ratios at
individual positions(aggregates).
(iv) Diagnostic methods for the monitoring of ma-chinery
condition, permanent online measurementsof selected parameters,
especially temperature, vi-bration in the meaning of ISO,
high-frequency vi-brations and acoustic emission, and
lubricantmonitoring from the point of view of the frictionmode.
(a) (b) (c)
Figure 1: Demonstration of gear toothing damage.
Figure 2: Example of emergency repair of the cogwheel by
welding.
4 Advances in Materials Science and Engineering
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3.2. Materials and Methods. Vibrodiagnostic measurementis a
non-disassembly and nondestructive diagnostics ofrotary machines,
which allows a consistent assessment of themachine’s technical
condition even without shutting downthe machine. -e measurement was
aimed at assessing theoperational status of two turbo generators
with different oilfillings using the technical diagnostics methods.
-ere aretwo ways to implement diagnostic methods, depending
onwhether the object being diagnosed is out of oper-ation—offline,
or in operation—online.
To assess vibration in the low-frequency area, the fol-lowing
were used:
(i) Velocity method (vibration speed), unit mm/s,
RMSdetection
(ii) In accordance with ISO10816-3: 2009, FFT (fast-Fourier
transform) spectrum for the 10–800Hzfrequency range
(iii) Enveloping acceleration, Eg, PtP detection, 50–1000Hz
frequency range, FFT spectrum, and timerecording
To assess vibration in the high-frequency area, the fol-lowing
were used:
(i) Acceleration measurement method (vibration ac-celeration),
unit g, PtP detection, Frequency rangeup to 20 kHz, FFT spectrum,
and time recording.
(ii) Enveloping acceleration method, Eg, PtP detection,frequency
range up to 10 kHz and up to 20 kHz, FFTspectrum, and time
recording.
(iii) A detailed vibration analysis to assess the conditionof
the gear unit toothing and rotors:
(a) Frequency spectrum analysis and vector ofimportant frequency
components (amplitudeand rotational frequency phase)
(b) Toothing components of vibrations and theirharmonic
multiples, relative shaft vibrationanalysis, and an analysis of a
shaft centerposition
-e following devices were used for the diagnosticmeasurement of
vibration (data collection) and analysis:
(i) MicrologGX frequency analyzer and data collector(ii)
AptitudeAnalyst SW environment(iii) -e manufacturer of SKF
Condition Monitoring
machinery (USA)(iv) Vibration sensor, Wilcoxon Research
Accelerom-
eter, SKF786M model, sensitivity 100mV/g, andfrequency range
1–20,000Hz
3.2.1. Method of Cyclic Time-Averaging (CTA)
(i) -e advanced analysis of the condition of thetoothing
(ii) A detailed vibration analysis to assess the conditionof the
toothing and gear rotors, in particular, fre-quency spectrum
analysis, vector of important
frequency components (in particular amplitude androtational
frequency phase), toothing components ofvibrations and their
harmonic multiples, relativeshaft vibration analysis, and an
analysis of a shaftcenter position
3.2.2. Lubricating Oil Analyses
(i) -e kinematic viscosity of the oil as a proportion ofthe
dynamic viscosity and density of the fluid
(ii) Water content(iii) Analysis of elements of additives
concentration(iv) Reichert lubricity test(v) FTIR spectra
4. Experiments and Measurement Results
Figure 3 shows continuous online monitoring of selectedoperating
parameters for 24 hours. -e black color indicatesthe trend of
high-frequency absolute vibrations up to 20 kHzfor detecting and
assessing the gear teeth engagement.
4.1. Frequency Analysis of Signal: High-Frequency Area.-e
waterfall graph of the frequency spectra in Figure 4displays the
dynamic signal area within high-frequency areaof absolute
vibrations (acceleration up to 20 kHz). Dominantfrequency
components correspond to the gear teeth en-gagement frequency and
harmonic multiples + sidebands.
4.2. CTA Analysis and Graph of Sprocket Vibration Profile.Figure
5(a) displays the calculated vibration profile for quietgear
operation without high amplitudes on the gear teethengagement
frequency. Figure 5(b) shows the analysis of thesignal from
unstable operation. It is obvious that the gearteeth engagement
during instability is markedly de-teriorated. -is has a direct
effect on the rapid wear of thetoothing contact surfaces and thus
the change in micro-geometry. Early toothing failure (fatigue
damage and pit-ting) can also occur with the increase of slip at
the expense ofthe slew.
4.3.Assessmentof theLubricantCondition. Two identical setsof
turbo generators TG3 and TG4 were in operation with theusage of
gear unit. -e analysis of unstable high-frequencyvibrations was
performed on a TG4 machine where thisunfavorable phenomenon occurs.
On the TG3 machine,such symptoms of occasional significant
deterioration ofgear teeth engagement were not detected. Gear units
do nothave the same oil content. In both cases, ISO VG 46
ki-nematic viscosity turbine oil was used, but the
additiveconcentration and EP and WP properties of the oils
weredifferent. -erefore, a lubricant analysis was carried out.
-efollowing part of the paper presents the differences found
byanalyzing the chemical and physical properties of the TG3and TG4
operating lubricating oils.
Advances in Materials Science and Engineering 5
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�e kinematic viscosity is the same for both oil llings(Table 1);
di�usion is in line with the recommendations forsafe operation of
the machine in terms of friction mode.
�e water content is increased in both cases (Table 1),slightly
above the recommended limit. �is phenomenoncould be assumed because
of the fact that it is a turbogenerator, the operating medium of
which is hot steam.Increased water content is an accompanying
feature of theoperation of these machines. Turbine oils are doped
with theemphasis on ensuring high oil resistance even when
oper-ating with increased water content.
4.4. Concentration of Additives. Table 2 shows a
signicantdi�erence in the concentration of typical additive
elements(P, phosphorus; S, sulphur) in favor of the TG3 lling.
Additives determine lubricating EP and WP propertiesof oil (when
dening lubricating oils, new lubricant prop-erties are often
required, such as reduced wear in borderlubrication mode—WP
additives; high pressure and impactload resistance—EP additives;
and good anticorrosion andantifoaming properties) during operation,
especially at highspeeds and contact pressures in oil lm
(toothing).
It is important to balance the additives to achieve theoptimum
performance and stability of lubricating oils.
4.5. Reichert Lubricity Test. Table 3 lists the results of
theReichert test for both oil types examined.�e test is designed
todetermine the point of formation of a lubricating lm betweentwo
test surfaces.�e test starts as a sliding contact between
thesurfaces and progresses to being hydrodynamically lubricated
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The areas of “instability” and high signal of acc 20kHz
Figure 3: �e areas of “instability” and high signal of acc 20
kHz and “quiet” operation without signs of instability.
3,450 3,500 3,550 3,600 3,650 3,700 3,750 3,800 3,850 3,900
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1 × FzArea of instability:gear teeth engagement frequency
Figure 4: Dynamic signal area in the high-frequency acceleration
range up to 20 kHz.
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due to the formation of a lubricating film between the
surfaces.-is change is a result of the contact geometry
progressingfrom a point contact to an area contact.-e rated
parameters ofthis test are the load bearing capacity of the
lubricant film andthe abrasive wear [16].
Table 3 shows a significant difference in lubricatingproperties
again in the favor of TG3.-e result is in line withthe chemical
analysis of the lubricant additives.
4.6. Comparison of FTIR Spectroscopy. FTIR stands
forFourier-transform infrared, the preferred method of
infrared spectroscopy. Comparison of the FTIR spectra inFigure 6
is in the area of about 1000 cm–1 and shows thedifference in oil
filling TG3 relative to TG4 in terms oflubricant additives.
In the assessed spectrum, the P-O-C linkage signal isdifferent,
confirming the different chemical compositionsand the different
additive technologies for TG3 (blue) andTG4 (red) oil fillings:
Oil sample analysis and comparison of additives con-sumption
from the TG3 gear unit in Figure 7 are shown asfollows:
(i) Draught oil, new, unused (marked in blue) (EssoTeresstic
EP46)
(ii) Oil removed from the TG3 gear unit, used (markedin red)
-e FTIR spectrum shows a decrease in concentrationand
consumption of additives in the area of about 1000 cm–1.It is a
mechanism of gradual decrease of additive elements inthe real
operation of contact surfaces (gear teeth engage-ment). When
assessing the rate of element loss, trendanalysis shows the
following:
(i) Difficulty of gearing operation in terms of frictionmode
(ii) -e “quality” level of the oil filling and the
micro-geometry of the side of the toothing
5. The Evaluation of Results of the AppliedMeasurements and
Analyses: Discussion
-e turbo-generator unit with the gear unit transmits apower of
50MW. Industrial practice shows several de-ficiencies that occur
during the operation of machines insuch an assembly. All
deficiencies have a direct effect on the
Pk: 0.3141Var: 0.0092Std: 0.0959
Speed 9446.86RPM >> 1x > 1x
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significant reduction in service life and/or reliability
ofmachine operation. -is paper describes and approaches
thetechniques of technical diagnostics that have been applied inour
research. -e first step was the online monitoring ofhigh-frequency
absolute vibrations during 24-hour opera-tion of the turbo
generator. -e next step was the frequencyanalysis of the signal in
the high-frequency area where thedynamic signal area was also
displayed in the high-frequencyarea of the absolute vibrations
using the frequency spectra.Subsequently, a CTA analysis was
performed to show thegear teeth engagement. After this analysis, it
was shown thatthe gear teeth engagement during instability was
signifi-cantly impaired, resulting in changes in toothing
surfacesand microgeometry.-is causes early toothing failure due
to
its subsequent damage. -e final step was to assess thecondition
of two different lubricants. Kinematic viscosity,water content,
additive concentration, Reichert test, andFTIR spectrum were
examined.
-e analyzes performed confirmed the assumption of asignificant
correlation between the measured dynamic pa-rameters and the
friction mode. -e tests show a relativelystrong correlation of the
high-frequency vibrational signal ofabsolute vibrations on the
frequency of gear teeth engage-ment, amplitude increase well above
the recommended limit(Alarm2—Danger), with inappropriate gear teeth
engage-ment (the slew/slip ratio shown in the CTA
analysis).Furthermore, we examined friction mode and
lubricantcondition, additive element concentration with respect to
EP
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
Abso
rban
ce
1800 1600 1400 1200 1000 800Wavenumbers (cm–1)
Lubricating additives
Turbine oil, TG-3, dark 21.1.2013, k. 0.1mmTurbine oil, TG-4,
dark 21.1.2013, k. 0.1mm
Figure 6: Comparison of the FTIR Spectra in terms of lubricant
additives.
2.6
2.4
2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
Abso
rban
ce
1800 1600 1400 1200 1000 800Wavenumbers (cm–1)
TG-3 oil, used
Esso teresstic EP 46
Esso teresstic EP 46, turbine oil, k. 0.1mmTurbine oil, TG-4,
light, 21.1.2013, k. 0.1mm
Figure 7: Comparison of FTIR spectra in terms of consumption of
additives in the TG3 gear unit.
8 Advances in Materials Science and Engineering
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and WP lubricant properties, and carried out the trendanalysis
on oil lubricant properties. In order to avoid thisadverse effect
in the future, it is necessary to perform regularmonitoring of
these selected parameters and to examine thephysical/chemical
properties of the lubricant, with an em-phasis on EP and WP oil
properties. In addition, it is ad-visable to optimize and choose
the oil filling with regard tothe design of the machine, the
operating conditions of thegear unit, the presence of water, the
thermal dilatations, therelative speed of the contact surfaces, and
the transmittedpower (contact pressures with respect to
microgeometrywear).
6. Conclusion
In technical practice, vibrodiagnostics plays an
irreplaceablerole in assessing the current state of technical
systems. -ebasis is the analysis of the vibration signal, which
representsinformation about the current operating condition, or
aboutchanges that occurred during the operation of the systemunder
examination. By applying vibrodiagnostic tools, it ispossible to
identify the following unwanted machine andequipment states:
(i) Imbalance(ii) Shafts—couplings misalignment(iii) Bearing
defects and wear(iv) Rotor eccentricity(v) Mechanical loosening(vi)
Bending of the shaft(vii) Errors in structures(viii) Gearbox
failures
Based on the categorization of cog gear transmissiondefects, it
is possible to identify the relevant malfunctions:damage due to
fatigue (contact fatigue and fatigue breakageof the cog), damage
caused by other factors (abrasive wear ofcog surfaces by particles
in the lubrication system, adhesionwear—formation of microscopic
welds, and subsequentbreakage), permanent deformations, run-out,
and pro-gressive pitting [17]. When the cogs engage, they roll
awayand slide. Such rolling and sliding motion has a
significanteffect on the lateral cog surface wear [18]. Operating
con-ditions that considerably determine the extent and type
ofdamage are the magnitude of the border cog load, the pe-ripheral
speed of rotation, and the quality and properties ofthe lubricant
applied. A nonnegligible role in the possibledamage to gearbox cogs
plays the manner and the nature ofinstallation of the technical
system. Axial misalignment ofthe driving and the driven shaft
generates dynamic forcesthat contribute to the wear of bearings,
shafts, and cogwheels[19].
-is paper describes the application of vibrodiagnosticand
tribodiagnostic instruments in assessing the operatingstatus of the
gearbox in the technical system of a turbogenerator. -e
manifestations of impaired gearbox cogengagement were recorded by
high-frequency vibrationanalysis on the turbo-generator gearbox
marked by the TG4
symbol. In case of the said gearbox, the friction mode and
oilcondition as well as the additive concentration with respectto
EP and WP properties of the lubricant and the trendanalysis of the
elements determining the lubricating prop-erties of the oil were
then assessed. -e results were com-pared with the results of the
TG3-marked oil filling analyses.In both cases, turbine oil with
different concentrations of EPand WP additives was applied. -e
analysis and the sub-sequent comparison of the chemical and
physical propertiesconfirmed operational problems in case of the
gearboxidentified as TG4.
-e study has confirmed the existence of a correlationbetween the
monitored dynamic parameters and the currentfriction mode. From the
vibration spectra analyses, in-creased levels of the cog engagement
component and theirharmonic multiples are visible. Analysis of
profile chartsindicates a significant deformation at the output
from thegearbox from transverse force. One of the causes may be
aninappropriate installation of the clutch between the gearboxand
the generator. -e graph also shows insufficientsmoothness of the
cog engagement.
Continuous checking of the lubricant level in rotarymachines is
important for maintaining high reliability of thetechnical system.
Suitable lubricant selection may signifi-cantly extend the service
life. In addition, it is necessary totake into account all the
important circumstances and as-sumptions and to include those
considerations in the finalapplication.
Applied measurements and analyzes have confirmedimportant
information for practice, namely, the existence ofa direct link
between the level of dynamic parametersassessed in the form of
high-frequency vibrations andacoustic emission and the real state
of lubrication of thegearing contact surfaces. -e purpose of
lubrication is tominimize friction, to dissipate the heat generated
by friction,and, of course, to reduce wear on the tooth teeth of
the gears[20]. -e geometrical shape of the flanks of the teeth
de-termines the rolling and sliding movements so that the
gearsoften work in the mixed friction area. -is is confirmed bythe
types of possible gearbox damage and measurable powerlosses
[21].
-e research has led to a recommendation given to
theturbo-generator system operator on how to optimize the
oilfilling and how to select the right one with regard to
themachine design, gearbox operating conditions, presence ofwater,
transmission performance, and so on.
Based on the conducted measurements and analyzes, itcan be
stated that the physical and chemical stabilities of thelubricant
significantly affect the reliable operation of thefriction nodes of
the technical systems. Lubricant degra-dation can be caused by
various influences including in-creased operating temperature,
mixing of lubricants, moistor dusty environment, oxidation, loss of
additives, increasedimpurity ratio, and so on. Lubricating oil
additives de-termine the EP and WP lubricity properties of the oils
inservice, especially at high speed and contact pressure at theoil
film site, which is the case of gear transmission. -epurpose of
adding additives to the lubricant is to improve itsperformance
properties, such as separation from air or water
Advances in Materials Science and Engineering 9
-
and also to suppress unwanted phenomena (tendency toparaffin
formation at low operating temperatures). However,over time, the
additives are lost, their volume is reduced, andthe lubricant’s
operating properties must be restored.
-e loss of additives depends on the type of additives aswell as
the operating conditions, partly on the temperatureand the presence
of water. Some additives condense andseparate from the base oil at
low temperatures. Many ad-ditives are sensitive to hydrolysis, and
the presence of waterin the lubricant often damages the additive
system. Con-tinuous checking of lubricant condition and life is one
of themost important activities related to the application
ofproactive maintenance methods [21].
Data Availability
-e data used to support the findings of this study are in-cluded
within the article.
Conflicts of Interest
-e authors declare that they have no conflicts of interest.
Acknowledgments
-e authors thank the Ministry of Education of SlovakRepublic for
supporting this research by the grant KEGA001TUKE-4/2018
(Implementation of concurrent engi-neering philosophy to
educational tool in the field ofcomputer-aided technological
preparation) and Slovak Re-search and Development Agency under the
contract no.APVV-16-0355.
References
[1] R. Kumar, S. Chatopadhyaya, S. Hloch, G. Krolczyk, andS.
Legutko, “Wear characteristics and defects analysis offriction stir
welded joint of aluminum alloy 6061-T6,” Eks-ploatacja I
Niezawodnosc—Maintenance and Reliability,vol. 18, no. 1, pp.
128–135, 2016.
[2] G. Krolczyk, S. Legutko, and A. Stoic, “Influence of the
cuttingparameters and conditions onto surface hardness of
duplexstainless steel after turning,” Tehnicki
Vjesnik—TechnicalGazette, vol. 20, no. 6, pp. 1077–1080, 2013.
[3] S. Legutko, “Development trends in machines
operationmaintenance,” Eksploatacja I Niezawodnosc—Maintenanceand
Reliability, vol. 2, no. 42, pp. 8–16, 2009.
[4] K. Lu, L. He, and Y. Zhang, “Experimental study on
vibrationreduction characteristics of gear shafts based on ISFD
in-stallation position,” Shock and Vibration, vol. 2017, Article
ID7246356, 10 pages, 2017.
[5] R. Fargère and P. Velex, “Some experimental and
simulationresults on the dynamic behaviour of spur and helical
gearedtransmissions with journal bearings,” Advances in
Tribology,vol. 2012, Article ID 163575, 9 pages, 2012.
[6] R. Bajric, N. Zuber, G. A. Skrimpas, and N.
Mijatovic,“Feature extraction using discrete wavelet transform for
gearfault diagnosis of wind turbine gearbox,” Shock and
Vibration,vol. 2016, Article ID 6748469, 10 pages, 2016.
[7] N. Barbieri, G. de Sant’Anna Vitor Barbieri, B. M.
Martins,L. de Sant’Anna Vitor Barbieri, and K. F. de Lima,
“Analysis of
automotive gearbox faults using vibration
signal,”MechanicalSystems and Signal Processing, vol. 129, pp.
148–163, 2019.
[8] Z. Chen, C. Li, and R.-V. Sanchez, “Gearbox fault
identifi-cation and classification with convolutional neural
networks,”Shock and Vibration, vol. 2015, Article ID 390134, 10
pages,2015.
[9] M. Strączkiewicz and T. Barszcz, “Application of
artificialneural network for damage detection in planetary gearbox
ofwind turbine,” Shock and Vibration, vol. 2016, Article ID4086324,
12 pages, 2016.
[10] N. K. Myshkin and L. V. Marková, “Trends in on-line
tri-bodiagnostics,” inOn-Line ConditionMonitoring in
IndustrialLubrication and Tribology, pp. 203–223, Springer,
Cham,Switzerland, 2018.
[11] A. Glowacz, W. Glowacz, Z. Glowacz, and J. Kozik,
“Earlyfault diagnosis of bearing and stator faults of the
single-phaseinduction motor using acoustic signals,”
Measurement,vol. 113, pp. 1–9, 2018.
[12] J. Furch, J. Glos, and T. T. Nguyen, “Identification of
thetechnical condition of roller bearings by means of
vibro-diagnostics and tribodiagnostics,” Transactions of
FAMENA,vol. 41, no. 3, pp. 99–113, 2017.
[13] J. Glos, “Tribologic methods used for an engine
diagnostic,” inProceedings of the Intelligent Technologies in
Logistics andMechatronics Systems (ITELMS 2011), pp. 9–13,
Panevėžys,Lithuania, May 2011.
[14] E. M. Portnov, K. Z. Lin, V. V. Kokin, and A. K.
Myo,“Method for detection of failures in complex process
controlsystems,” in Proceedings of the 2017 IVth
InternationalConference on Engineering and Telecommunication
(EnT),pp. 145–149, IEEE, Moscow, Russia, November 2017.
[15] P. Jayaswal, A. K. Wadhwani, and K. B. Mulchandani,“Machine
fault signature analysis,” International Journal ofRotating
Machinery, vol. 2008, Article ID 583982, 10 pages,2008.
[16] M. Batsch, T. Markowski, S. Legutko, and G. M.
Krolczyk,“Measurement and mathematical model of
convexo-concaveNovikov gear mesh,” Measurement, vol. 125, pp.
516–525,2018.
[17] I. Kuric, M. Cisar, T. Novosad et al., “Experimental device
forpracticing routines of machine tool precision
measurement,”Academic Journal of Manufacturing Engineering, vol.
13, no. 1,pp. 39–44, 2015.
[18] G. M. Krolczyk, J. B. Krolczyk, S. Legutko, and A.
Hunjet,“Effect of the disc processing technology on the vibration
levelof the chipper during operations process,” Technical
Gazette,vol. 21, no. 2, pp. 447–450, 2014.
[19] I. Vojtko, P. Baron, M. Pollák, and J. Kaščak,
“Examining theeffect of alignment of the rotor of the emissions
exhaust fan onits operating parameters,” Advances in Materials
Science andEngineering, vol. 2019, Article ID 4985395, 13 pages,
2019.
[20] R. W. Maruda, E. Feldshtein, S. Legutko, and G. M.
Krolczyk,“Analysis of contact phenomena and heat exchange in
thecutting zone under minimum quantity cooling
lubricationconditions,” Arabian Journal for Science and
Engineering,vol. 41, no. 2, pp. 661–668, 2016.
[21] P. Dálik, “Diagnostika hydraulických olejov,”
Tribotechnika,vol. 4, pp. 18-19, 2011.
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