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Investigation of thurst bearing high temperature in gas turbine
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IJREC (2017) 1–13 © JournalsPub 2017. All Rights Reserved Page 1
International Journal of Renewable Energy and Its Commercialization
Vol. 3: Issue 1
www.journalspub.com
Article Type: Research Article
Investigation of Thrust Bearing High Temperature in Gas
Turbine
F. Al Jabri, S. Feroz*
Caledonian College of Engineering, Seeb, Sultanate of Oman
ABSTRACT
Gas turbines in electric power generation and various industrial applications have made
remarkable improvement in the current scenario in terms of size, efficiency and prominence.
In order to maintain the sustainability of high level performance and increased reliability of
the gas turbine, it has become mandatory to carryout in depth diagnostic methods and frame
maintenance plans. This paper mainly concentrates on the analysis of the repeated tripping
of gas turbine in Oman oil industry, due to its thrust bearing high metal temperature issues.
Root cause analysis, visual and borescopic inspections, lube oil analysis were carried out to
indentify the root causes for high temperature and came up with successful results for
restoring and ensuring reliable operation of gas turbine.
Keywords: Borescope technique, fishbone diagram, gas turbine, lube oil analysis, root cause
analysis
*Corresponding Author
E-mail: ferozs2005@gmail.com
INTRODUCTION
Gas turbines perform a vital link within oil
industry’s electrical grid that supplies
energy to the majority of upstream
facilities and all essential power
equipments. The reliability of the gas
turbine is paramount importance of
uninterrupted power generation for
efficient oil production. Gas turbine is a
type of internal combustion engine that
produces great amount of power as a form
of hot gases in result of fuel and air
mixture continuous burning. That power is
customized and widely used to drive prime
movers in electric power plants,
petrochemicals processes, oil and gas
sector, rockets, aircrafts and in modern
weaponry. Gas turbines utilize variety of
fuels e.g. natural gas, fuel oils and
synthetic fuels. More or less 55 to 65 % of
power produced by the turbine is used to
drive axial air compressor and remaining
power can be utilized to drive a prime
mover. Optimum support and positioning
needed by rotating components is provided
by bearings in the gas/steam turbines. For
radial support, journal or roller bearings
are used while the axial positioning is
generally delivered by thrust bearings. In
aircraft jet engines, ball or roller bearings
are mainly used for radial support, while in
almost all-industrial gas turbines journal
bearings are used. Key components of an
ideal bearing arrangement include a long
shelf-life, high degree of reliability, and
economic efficiency. To achieve this
target, the design engineers consider all the
important parameters viz., load and speed,
temperature of lubrication, shaft
arrangements, shelf-life,
mounting/demounting, noise and other
environmental factors. The main function
of a thrust bearing is to repel the thrust
unbalance caused by working elements of

High Temperature Issues in Gas Turbine Al Jabri and Feroz
the turbomachine while retaining the rotor
position within tolerable limits. After
thorough analysis, the size of thrust
bearing is selected so as to support the
load in the most efficient way possible.
Several tests have proven that thrust
bearings are restricted for load capacity by
the strength of babbitt surface within high
load and temperature zone. In normal
steel-backed babbitted tilting-pad thrust
bearings, this capacity falls within 250–
500 psi (17 and 35 Bar) average pressure.
The average pressure is governed largely
by temperature accumulation at the surface
and pad crowning. The thrust-carrying
capacity can be enhanced with optimum
pad flatness and removing overloaded heat
from the zone. Using high thermal
conductivity backing materials of optimum
thickness and support, the maximum
continuous thrust limit can be enhanced to
around 1,000 psi or even more. This new
limit can be used in two ways: first, it may
increase the safety factor and enhance the
surge capacity for a given size bearing.
Second, it may decrease the thrust bearing
size and subsequently the losses made for
a given load. Since, copper and bronze are
better options as bearing materials owing
to their higher thermal conductivity as
compared to the conventional steel
backing, it is likely to reduce the babbitt
thickness to nearly 0.010–0.030 of an inch
(0.254–0.762 mm). Embedded
thermocouples and RTDs when properly
positioned, indicate all kind of distress that
might occur in the bearing. Temperature
monitoring systems have shown more
accuracy than the axial position indicators,
as the latter tend to have linearity problems
at high temperatures [1].
In the present research work, failure
analysis of gas turbine thrust bearing in
Oman oil industry and the healthy way to
sustain the operational reliability by
averting recurrence of failures was carried
out. Since the modes of failures are
different, it demands different types of
solution. A systematic technical
methodology, root cause analysis of
bearing failures was carried out by
considering conditional monitoring
techniques and its recommendations.
Along with that it is highly advisable to
implement an appropriate maintenance
technique which is capable of detecting
any sign of premature failure of gas
turbine thrust bearing.
MATERIALS AND METHODS
Standard procedures viz., fishbone
diagram and root cause analysis based on
the available data and historical trend was
used in statistical analysis in order to find
the cause of gas turbine bearing failures.
Fishbone diagram (Ishikawa diagram),
also referred as the cause-and-effect
diagram, is a visualization tool for
classifying the possible causes of a
problem in order to recognize its root
causes. Dr. Kaoru Ishikawa, a Japanese
quality control expert, invented the
fishbone diagram to help his employees
avoid solutions that merely address the
symptoms of a much larger problem
whether technical or organizational issue
[2]. Fishbone diagram is useful in
brainstorming sessions for making
conversation more focused and thoughtful.
After the group has brainstormed all the
possible causes for a problem, the
facilitator helps the group in rating the
potential causes according to their level of
importance and formulate a hierarchy. The
appearance of the diagram looks similar to
a fish skeleton. The typical way to read a
fishbone diagram is to move from right to
left, with each large “bone” of the fish
branching out to include smaller bones
containing more details. Fishbone
diagrams are used in the “analyze” phase
of Six Sigma’s DMAIC (define, measure,
analyze, improve, and control) approach to
problem solving.
Figure 1 shows the fishbone diagram to
troubleshoot the high bearing metal
temperature of the active thrust bearing
and to find out the actual root cause with

Vol. 3: Issue 1
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appropriate solution to resolve the issue.
Various condition monitoring techniques
were adopted to find out the root cause for
high temperature in thrust bearing which
includes borescope technique, X-ray
diffraction (XRD), lubrication contaimant
analysis, mean time between failures
(MTBF), realibility and availability
techniques.
Fig. 1. Fish bone diagram.
Borescope is an optical device that
comprises a rigid or flexible tube with an
eyepiece on one end and an objective lens
on the other. The two lenses are connected
with each other through a relay optical
system. In some cases, the optical system
is surrounded by optical fibers that helps in
visualization of remote objects. The
objective lens forms an inner image of the
visualized object which is then magnified
by the eyepiece and presented into the
viewer’s eye [3]. XRD which is based on
the principle of dual wave/particle nature
of X-rays is used to evaluate the structure
and composition of compounds. This
technique is also used for characterization
of the compounds based on their
diffraction pattern. XRD enables detection
of dust & debris deposition in the turbine
assembly which otherwise might cause
heavy thrust to the rotor and to the bearing
leads that leads to metal temperature
(BMT) failures [4]. Lubricant contaminant
analysis is a periodical inspection and
survey to conduct lube oil analysis to
determine the contaminant of the lube oil
which is another major cause of the
bearing failures. MTBF refers to the
amount of time that elapses between one
failure and the next. The total time
required for a device to fail and that failure
to be repaired. The basic calculation to
determine MTBF is purely the reciprocal
of the failure rate function. MTBF can be
calculated by using Equation 1 [5].
MTBF = T/r (1)
where MTBF is the mean time between to
failure, T the total running time during an
investigation period for both failed and
non-failed items, and r is the total number
of failures occurring during the
investigation period.

The reliability of the system is very much
affected by its reliability components,
quality, design and even its structure,
while its availability is affected [6].
Availability of equipment is the time the
equipment is operable condition as a
proportion of the total time. it clearly
depicts the availability of the gas turbine
which is alarming the asset manager to do
further assessment and necessary
rectification.
Reliability calculated based on the
simplified formula as shown in Equation 2
[5].
Reliability = 1– e–1/MTBF
(2)
Availability calculations are made based
on the simplified formula as shown in the
Equation 3 [5].
Availability = MTBF/(MTBF+MTTR)
(3)
where MTTR is the mean time to repair.
In the present research studies, a
comprehensive analysis was carried out to
find the root cause of the repeated tripping
of gas turbine in Oman oil industry, due to
its thrust bearing high metal temperature
issues.
RESULTS AND DISCUSSIONS
Deterioration of Oil Quality Based on
Statistical Surveys
The varnish formation rate which was
initial considered to be the reason behind
the high bearings temperature but later it
was found to be a consequence of
overheating and cannot be considered as a
root cause. The oxidation is an obvious
result of high lube oil which increases to
double for around 10o
C rise in the
temperature. From the conducted
investigation it was found that the high
bearings temperature was caused by either
poor performance of the lube oil cooler
system or insufficient bearings clearance
and misalignment or by poor maintenance
management.
The analysis of temperature of gas turbine
shows a high inlet lube oil temperature and
this strongly raises a concern about the
efficiency of the lube oil cooler including:
cooling fan and temrature conrol valve
(TCV) settings. It was also found that
there was no sufficient clearance in the
removed and installed bearings. However,
as kind of mitigation to avoid high
membrane patch colorimetry (MPC), it is
strongly recommended to install special
lube oil filters to deal with the varnish
deposition. It was also recommended to
change lube oil of gas turbine due to high
level of varnish contamination. Table 1
shows the lube oil sample analysis data of
gas turbine that depicts the formation of
varnish and considered to be the moan
cause for bearing overheating.
Table 1. Oil sample analysis of GT on 14/09/2015.
Oil type Turbo T100 Limits
Data sampled 14-Sep-16 –
Data analyzed 15-Sep-16
Oxidation (abs/mm2
) 5.3 N/A
TAN (mgKOH/g) 0.8 <0.4
Water (ppm) 800 <500
Viscosity @ 40°C (cSt) 86.46 39.1–52.9
Flash point (°C) >200 >160
Thrust Bearing Metallurgical Failure
Analysis
Once the formation of varnish was
confirmed for bearing overheating, to get
into the root cause, thrust bearing
metallurgical failure analysis was carried
out. The temperature of thrust bearing was
in increasing trend even though the
refurbishment of lube oil change sustained
for short duration. Checking the old
bearing conditions of gas turbine, the
effect of overheating was visible in terms
of rubbing damage which caused severe
surface erosion. This is due to improper

Vol. 3: Issue 1
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maintenance schedule and misalignment of
bearing. It was clear by reviewing the
historical data that changing the bearing
and lube oil sustained for about 6 months
before the same issue happens again. For
gas turbine, the change of lube oil did not
help to solve this issue which clearly
indicates the need for replacing the thrust
bearings too. The data analysis depicts that
for every 10°C increase in the operating
oil temperature, the rate of oil oxidation
doubles. Contact between moving and
stationary parts often causes damage due
to continuous rubbing. Constant and
multiple times rubbing can cut the grooves
within the shaft area. Heavy rubbing
causes high vibration which can overload
some bearings in the machine, causing the
oil wedge to break. The consequent results
include bearing damage which is followed
by overheating. The most common reasons
behind this issue in such applications can
be summarized in the following points:
 Inappropriate type/quality of lube oil.
 Lube oil inlet temperature too high.
 Over speed/excessive load.
 Insufficient lube oil flow due to lube
oil passage obstruction or oil seal
leakage.
 Insufficient bearing clearance.
 Particles accumulation in oil
scrubber/filters.
Design Verification
Design verification was carried out to
check incorrect machining; dimension;
babbitt quality and bearing fabrication as
per the vendor inspection and quality
check documents. No deviations made
from the vendor drawing. No visual
damages were found on the Pads. Also pad
seating was checked and no anomaly
noticed. The thickness of active thrust
bearing, thrust collar, shims were
measured on the upper half at three
locations with the rotor loaded on the
active side. The thickness measurements
were 6.566 for top, right and left. This
confirmed dimensional accuracy. Blue
contact check was performed for both
upper half (UH) and lower half (LH). One
of the pins in the LH was found protruding
out affecting contact negatively in that
area. Figure 2 shows the exact location
where the protruded pin location was on
pad 7 close to pad 8 that was showing high
temperature.
Fig. 2. Thrust bearing design verification.

Material Defects Verification
After design verification, a thorough
verification of material defects was carried
out. The thrust collar thickness was
measured in different locations and found
to be 2.925. This indicates no uneven
wear on thrust collar. Float check carried
out and recoded as 0.015 which is within
specification. A set (rotor axial position)
also checked and found to be within
specification. Casing alignment check was
inspected and all corrections were carried
out and new dowel holes were drilled in
the compressor discharge casing (CDC) to
main compressor casing (MCC) lower
vertical flange and also the machining of
the horizontal shims at outer
circumference height (H2) of bearing
housing. Complete torqueing of all lower
radial vertical flange bolts followed by a
final alignment check was done to ensure
the casings were perfectly aligned. The
journal bearing temperatures of left and
right pads indicates the casing and journal
bearings are aligned properly. However,
there is a significant differential of around
20°C seen between the two active pad
temperatures. This can happen when the
thrust bearing pads are unevenly loaded. In
this case Pad 8 ( bottom 7O’ clock
position) is showing 20°C more than the
pad 4 (2O’ clock position) as shown in
Figure 3.
Fig. 3. Thrust bearing arrangement.
This differential temperature of 20°C
between thrust pad 4 and 8 is seen since
Oct 2014 outage. There is no data
available prior to Oct 2014 outage to
verify if this differential was existed
before. Typically, the differential between
two measurements remains within 4–7°C.
Higher differential is an indication of
probably bearing housing deformation and
can be verified when the rotor is out. The
flatness of the thrust plate was checked on
a surface plate by blue check method.
Although the surface integrity appeared to
be acceptable, blue check did show
noncontact due to a pin protruding out.
Since this was considered a significant
observation for the thrust bearing assembly
to be replaced with a new set. The thrust

Vol. 3: Issue 1
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bearing that has come of the unit has been
send to the Vendor service shop for further
investigation. The thrust shims that were
installed were checked for its
flatness/dimensional integrity. There was a
0.004 difference in thickness of the shim
in the vertical and horizontal planes.
During inspection (Figure 4) it was
observed that the pin holding the pad
support had slipped more on to the plate
thus causing the thrust pad BMT raise.
From the review with the bearing vendor it
appears that the lower leveling link was
not properly seated over the dowel in the
thrust bearing housing. The link may have
been seated on top of the dowel pushing
the dowel out of the housing when loaded
and created non uniform overall assembly
thickness. This ascertains that one which
caused the high pad temperature. The
milled hole in the back of pad appears
slightly elongated. The dowels are press
fitted into the assembly. When assembled
they should be protruding approximately
0.27 from the housing trepan as shown in
Figure 5. Thrust bearing thermocouple
integrity and calibration check was carried
out and obtained its healthiness
Fig. 4. Thrust flames inspection.
Fig. 5. Bearing pad assembly.
Operation and Maintenance
Verification
After completion of material defects
verification, the operation and
maintenance verification was carried out.
Lube oil samples were tested and the
results furnished to vendor for reviewing.
The test results do not indicate serious
anomaly that can cause high BMT. Water
content is seen increasing and is at 91 ppm
getting close to limit of 100 ppm.
Cleanliness need to be improved and no oil
coking or electrical pitting observed on
pads was observed.

Borescopes are mainly used for optical
assessment of remote areas. They inspect
internal components of turbine and help in
recognizing any defects or imperfections
that might exist. Borescopes are
commonly used in visual inspection of
industrial gas turbines, steam turbines,
diesel engines, and automotive or truck
engines. Gas and steam turbines have care
and maintenance problems and therefore
need special attention. Excessive
maintenance associated with large turbines
are often costly and time-taking.
Borescope inspection helps in preventing
such unnecessary expenditure of money
and time. It was recommended to perform
on site borescope inspection of turbine and
compressor section for any potential
fouling/deposits. A detailed inspection of
thrust bearing, orifice, and inlet line for
any flow restriction is to be performed.
Finally, perform sample analysis of
debris/deposit. The borescope inspection
showed heavy deposits on stage-1/stage-2
nozzle in one month operation of the unit
with new nozzle as reference shown in
Figures 6, 7.
Fig. 6. Borescope of stage 1 nozzle.
Fig. 7. Borescope of stage 2 nozzle.
The turbine casing was removed and the
deposit surface was set for chemical
analysis and the results are shown in Table
2. The chemical composition of the sample
indicates calcium magnesium silicate as
the primary composition. Figure 8 shows
the X-diffraction comparison of the sample
collected with calcium magnesium silicate.
Table 2. Sample material composition.
Sample
description
%Ca %Mg % Fe %Ti %Mn %K %Na %Al %Si
GT after filter 34.8 0.82 2.96 0.86 0.05 0.48 1.76 7.6 11.9
GT sand
sample neat air
inlet
35.61 2.70 2.02 0.61 0.04 1.24 2.2 4.71 9.98
GT before air
inlet
41.94 1.91 3.15 0.58 0.08 0.93 1.67 7.81 14.3
GT 1st
STG
nozzle
41.17 1.20 3.78 0.87 0.04 2.26 1.77 7.71 18.8
Furthermore, analysis of the sample from
the stage 1 nozzle seems to be matching
with the analysis of sand/dust collected
from inlet system.

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Fig. 8. X-ray diffraction pattern.
A typical temperature profile of the turbine unit was shown in Figure 9.
Fig. 9. Turbine unit temperature profile.
It is seen that calcium magnesium silicate
can melt >1400–1500℃. This is a similar
temperature range what stage-1 nozzle
sees at higher loads. The X-ray diffraction
pattern of deposits from stage-1 nozzle is
matching with the pattern of sand from air
inlet system. Calcium magnesium silicate
seems to be having melting point ~1400–
1500℃. Combustion exit temperature is
also close to 1400–1500℃. So, most
likelihood of the deposits on stage-1
nozzle are from the sand coming from air
inlet system, getting melted in combustion
and deposits on the stage-1 nozzle, liner,
transition pieces etc in the hot gas path. A
restriction in the effective area of flow
path can influence the thrust on the
machine and can lead to elevated thrust
bearing temperature. Since the axial
position measurements are not showing
reliable readings, it is difficult to figure out
how much axial shift is causing due to the
flow restriction.
Operational and Maintenance Cost
Analysis for 2016 (OPEX)
The increase in the operational costs
(OPEX) has a direct impact on a business
performance. Due to growing trend of
failures, there are chances that the failures
may go beyond the repair level in near
future if proper measures are not initiated

appropriately. According to System
Application Programme (SAP), the gas
turbine machine failures are mostly related
to damage of bearing due to misalignment
of bearing; debris and contaminants
deposits in the stage blade causing rotor
imbalances and over thrust on bearing;
deterioration of lube oil quality; and or
inadequate maintenance management
schedule. This is vindicated by the
statistical analysis carried out in this
research work exclusively. This always
makes asset managers to make decisions to
come to a clear conclusion regarding the
overall scenario and a good indication of
possible failures and which is contributing
more on its critical failures. Table 3
depicts the failure contribution percentage
versus the amount spent in dollars for
various causes.
Table 3. Cost spent analysis for 2016.
Sl. no Reason Total spent ($) Failure contribution
1 Oil leak 5760 9.97%
2 Thrust bearing temperature high 7532 13.05%
3 Annual inspection and maintenance 16789 29.07%
4 Inlet guide vane (IGV) replacement 1278 2.22%
5 Cooler fan belt failure 750 1.30%
6 Leakage Inspection 2539 4.40%
7 GT oil filtration 5457 9.45%
8 Mechanical seal replacement 8548 14.80%
9 Main lube oil replacement 524 0.90%
10 Combustion chamber failure 8572 14.84%
The production loss is very huge in terms
of dollars calculated for the unit outage
due to this bearing failure. It is a very
heavy loss in terms of oil deferment and
gas deferment to Oil & Gas industry.
Oil Deferment Calculations for 7 Days
One gas turbine failure cause oil deferment
– 300 m3
/day
1 m3
of oil – 6 barrels (approx.)
Total barrel loss = 300 × 6 = 1800 barrels
One barrel cost – 53 dollars (current rate)
Total cost = 1800 × 53 dollars = 95,400
dollars/day
If bearing replacement took minimum 7
days of outage of GT, then
Total oil deferment to the company for 7
days = 95,400 × 7 = 667,800 dollars
Total oil deferment for 1 month = 95,400
× 30 = 2,862,000 dollars
Gas Deferment Calculations for 7 days
One gas turbine failure cause gas
deferment – 350,000 m3
/day
1 m3
of gas for calculation taken = 0.08
dollars (approx.)
Total cost = 350,000 × 0.08 = 28,000
dollars/day
If bearing replacement took minimum 7
days of outage of GT, then
Total gas deferment to the company for 7
days = 28,000 × 7 = 196,000 dollars
Total gas deferment for 1 month = 28,000
× 30 = 840,000 dollars
So Total loss for oil+gas deferment for 7
days = 667,800 + 196,000 = 863,800
dollars
If the maintenance is extended to 1 month
then the cumulative loss will be 2,862,000
+ 840,000 = 3,702,000 dollars
That is approximately 3.7 million dollars
per month. This is a heavy monetary loss
to the company. Table 4 shows the oil and
gas deferment cost for one day, 7 and 30
days, respectively.
Table 4. Oil and gas deferment cost.
1 day 7 days 30 days
Oil deferment, $ 95,400 667,800 2,862,000
Gas deferment, $ 28,000 196,000 840,000

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Table 5 and Figure 10 show the gas turbine maintenance cost analysis record.
Table 5. Gas turbine maintenance cost analysis.
1 day 7 days 30 days
Spare part 75,000 100,000 1,500,000
Man power 50,000 1,000,000 300,000
Loss of revenue oil 95,400 667,800 2,862,000
Value of gas burnt 28,000 196,000 840,000
Fig. 10. Gas turbine maintenance cost analysis (cumulative).
Gas turbine sustainable operation is so
paramount importance for continuous
improvement in production without any oil
deferment in oil industry and without any
power outage in power and allied units.
From the above statistical analysis it is
obvious that gas turbine failure were
reported several times which cause huge
revenue loss and increase the maintenance
cost considerably. The poor lube oil
quality & the contaminants in the lube oil
caused severe failures to the bearing which
ultimately made the unit outage due to the
component failure leading to prolonged
shut down and production loss. Also the
poor air inlet quality which ultimately
caused contaminants deposit and debris in
the turbine component which leads to
severe thrust and strain to the bearing pad
causing BMT failures end up with unit
outage posing long shutdown and increase
the maintenance cost. With the aid of fish
bone diagram and using root cause
analysis, a statistical analysis was carried
out in methodological way. Using
analytical technique such as Borescopic
Analysis and X-ray diffraction technique
the failure component will be detected
much earlier and the effect of the BMT
failure will be minimized by a quality
periodical maintenance and corrective
maintenance schedule. Also, by scheduling
the lube oil sample analysis the
contaminants will be detected earlier and
further deterioration of lube oil quality will
be minimized and the life cycle of the
bearing will be improved by better
engineering modification and replacement
of oil whenever necessary. This will
prevent the failures of the costly internal
30 days
7days
1day
$
Gas Turbine Maintenance Cost Analysis

parts of gas turbine and avert the unit
outage considerably. A better quality
maintenance management technique based
on Total Productive Maintenance (TPM)
technology will alleviate the problems and
make more production oriented. Based on
the above analysis and discussion the
following conclusions, future
accomplishments and recommendations
were obtained in this project which will be
very much useful for averting such failures
in any type of gas turbines in future.
RECOMMENDATIONS
 Suggesting for better quality air inlet
filter efficiency improvement by
providing high microns size pre filter
with dedicated self-cleaning pulse
generated filter as secondary one to
prevent the inlet air contaminants with
dust, sand and other tiny debris which
cause nozzle, stationary and moving
parts erosion causing severe thrust to
rotor shaft to the bearing. By this
augmented technology the life cycle of
the turbine parts especially BMT
failure will be prevented and enhance
the energy efficiency too. This will
prevent unnecessary unit outage
leading to power loss, heavy
production loss of oil deferment.
 A better quality maintenance
management technique based on TPM
(Total Productive Maintenance)
technology will alleviate the problems
& make more production oriented.
TPM is team based approachment. All
the discipline must work
collaboratively in safe manner in order
to achieve zero defects, zero
downtime, zero incident and zero
speed losses which resulting in
maximizing the overall equipment
effectiveness of the asset/plant.
 The fundamental standard of TPM is to
allow the employees to be involved
with the process of the improvement to
avoid unplanned equipment downtime
and reduce the waste. As the objective
was to lower the costs and improve
return on assets, the basic asset care
philosophy is quality preventive
maintenance and reliability corrective
maintenance technique to be
implemented.
 Periodical inspection such as visual,
borescopic and lube oil sampling for
cross checking the contaminants. In
extreme condition due to over fouling
or deposition, special technique such
as X-ray diffraction analysis will aid to
trouble shoot the problem in easier
manner and minimize the production
loss due to unnecessary equipment
outage and improve the energy
efficiency considerably.
 Recommended to enhance the lube oil
quality standards from contaminants
such as moisture, sand and debris. A
high efficiency Duplex filter system
and periodical inspection and
replacement of filter cartridges if
needed.
 A dedicated oil centrifuge purifier unit
free from moisture which will improve
the quality of oil from moisture can be
provided.
 A periodical frequency of lube oil
sampling to analyze early detection of
deterioration of oil quality and if
necessary replacement of it to enhance
the gas turbine bearing life cycle.
 A dedicated degassing system in the
lube oil reservoir tank to improve the
oil quality free from contaminants.
 Developing a long term asset
management strategy to analyses the
assets that require immediate
replacement or the major repairs in the
coming years.
 Developing a short term and long term
maintenance strategy.
CONCLUSION
 The statistical analysis indicates that
the abnormal positioning of thrust
bearing due to one active thrust pad
protruding pin is the cause for non-

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uniform loading and high thrust pads
BMT.
 The flow restriction caused by deposits
on the stage-1nozzle is also
contributing to increased thrust on the
rotor that also contributes to high BMT
which vindicated by the X-ray
diffraction analysis.
 Periodical lube oil analysis in quantum
of survey to determine the
contaminants.
 Failure of the periodical maintenance
inspection.
ACKNOWLEDGEMENT
The authors would like to acknowledge Mr.
S.N.R. Ramanuja and Eng. Said Al Mamari
for their support during the research work.
REFERENCES
[1] M. P. Boyce. Bearings and seals, In:
American Society of Mechanical
Engineers Gas Turbine Engineering
Hand Book. 4th ed. oxford: Elsevier;
2012, 557–604p.
[2] J. S. Sarazen. The tools of quality,
part II: cause-and-effect diagrams,
Qual Progress. 1990; 23(7): 59–62p.
[3] E. Roitberg, L. Shemer, D. Barnea.
Application of a borescope to studies
of gas-liquid flow downwards
inclined pipes, Int J Multiphase.
2006; 43(4): 499–516p.
[4] J. Epp. Material Characterization
Using Nondestructive Evaluation
(NDE) Methods: 4-X-Ray
Diffraction (XRD) Methods. 2016;
1(1), 81–124p.
[5] L. E. Miller, J. J. Kelleher, L.
Wong.Assessment of Network
Reliability Calculation Methods. J.
S. Lee Associates; 1993.
[6] A. Elsayed. Reliability Engineering.
2nd Edn. Hoboken, NJ, USA: John
Wiley & Sons; 2012. ISBN: 978-1-
118-13719-2
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