Energy and Power En gi neering, 2011, 3, 207-220
doi:10.4236/epe.2011.33027 Published Online July 2011 (
Copyright © 2011 SciRes. EPE
A Study of Implementation of Preventive Maintenance
Programme in Nigeria Power Industry—Egbin Thermal
Power Plant, Case St udy
Sunday Olayinka Oyedepo1, Richard Olayiwola Fagbenle2
1Mechanical Engineering Deparment, Covenant University, Ota, Nigeria
2Mechanical Engineering Department, Obafemi Awolowo University, Ile Ife, Nigeria
Received January 20, 2011; revised March 10, 2011; accepted March 31, 2011
Preventive Maintenance Programme consists of actions that improve the condition of system elements for
performance optimization and aversion of unintended system failure or collapse. It involves inspection, ser-
vicing, repairing or replacing physical components of machineries, plant and equipment by following the
prescribed schedule. It is commonly agreed nowadays that preventive maintenance programme can be very
successful in improving equipment reliability while minimizing maintenance related costs. The availability
of a complex system, such as steam turbine power plant is strongly associated with its parts reliability and
maintenance policy. That policy not only has influence on the parts’ repair time but also on the parts’ reli-
ability affecting the system integrity, degradation and availability. The objective of this paper is to study the
effects of Preventive Maintenance Programme (PMP) implementation on the performance of the Egbin 1320
MW thermal power plant in Nigeria. This paper considers the reliability and availability of the 6 × 220 MW
steam turbine units installed in the power station. The reliability and availability of the turbines are computed
based on a five-year failure database. The availability analysis of available data from 2005 to 2009 shows
different results for each unit and variation in availability for different year: availability of unit1 varies be-
tween 59.11% to 91.76%; unit 2, 64.02% to 94.53%; unit 3, 28.79% to 91.57%; unit 4, 80.31% to 92.76%
and unit 5, 73.38% to 87.76%. Unit 6 was out of service for the past 2 to 3 years. This indicates differences
in their systems installation maintenance and operation.
Keywords: Preventive Maintenance Programme, Power Plant, Reliability, Availability, Turbine
1. Introduction
Preventive maintenance scheduling of generating units is
an important task in a power plant and plays major role
in operation and planning of the system. The economic
operation of an electric utility system requires the simul-
taneous solution of all aspects of the operation schedul-
ing problem in the face of system complexity, different
time-scales involved, uncertainties of different order, and
dimensionality of problems [1].
Today, preserving and/or enhancing system reliability
and reducing operations and maintenance (O & M) costs
are top priorities in utilities. As system equipment con-
tinue to age and gradually deteriorate the probability of
service interruption due to component failure increases.
An effective maintenance strategy is essential in deliver-
ing safe and reliable electric power to customers eco-
nomically [2].
All utilities perform maintenance of system equipment
in order to supply electricity with a high reliability level.
The reliability of system operation and production cost in
an electric power system is highly affected by the main-
tenance outage of generating facilities. Optimized main-
tenance schedule could save millions of dollars and po-
tentially defer some capital expenditure for new plants in
times of tightening reserve margins, and allow critical
maintenance work to be performed which might not oth-
erwise be done. Therefore, maintenance scheduling for
electric utilities system is a significant part of the overall
operations scheduling problems.
Power plants components are able to remain in oper-
ating condition by regular preventive maintenance.
The purpose of maintenance scheduling is to find the
sequence of scheduled outages of generating units over a
given period of time such that the level of the energy
reserve is maintained [3].
In an increasingly competitive power delivery envi-
ronment, electric utilities are forced to apply more proac-
tive methods of utility asset management. One of the
main components of electric power delivery asset man-
agement is the capital budgeting and O & M of existing
facilities. Since in many cases the cost of construction
and equipment purchases are fixed, O & M expenditure
is the primary candidate for cost cutting and potential
savings. As system equipment continue to age and
gradually deteriorate the probability of service interrup-
tion due to component failure increases.
Electric utilities are confronted with many challenges
in this new era of competition: rising O & M costs,
growing demand on system, maintaining high levels of
reliability and power quality, and managing equipment
aging. Therefore, the health of equipment is of utmost
importance to the industry because revenues are affected
by the condition of equipment. When demand is high and
equipment is in working order, substantial revenues can
be realized. On the contrary, unhealthy equipment can
result in service interruption, customer dissatisfaction,
loss of good will, and eventual loss of customers. An
effective maintenance strategy is essential to delivering
safe and reliable electric power to customers economi-
cally [2].
The availability of a complex system, such as steam
turbine power plant, is strongly associated with the parts
reliability and the maintenance policy. That policy not
only influences the sub-system and parts’ repair time but
also their reliability affecting the system degradation and
availability. The maintenance policy philosophy is fo-
cused on the use of predictive or preventive maintenance
tasks that aim at the reduction of unexpected failures
during the component’s normal operation [4,5].
In a large enterprise, such as a power plant, keeping
asset reliability and availability, and reducing costs re-
lated to asset maintenance, repair and ultimate replace-
ment are at the top of management concerns [6]. In re-
sponse to these concerns, the Reliability Centered Main-
tenance (RCM) was developed by Stanley Nowlan and
Howard Heap in 1978 [7]. RCM has been defined for-
mally by Moubray [8] as ‘a process used to determine
what must be done to ensure that any physical asset con-
tinues to do whatever its users want it to do in its present
operating context’. For complex systems such as steam
turbines, the occurrence of unexpected component fail-
ures drastically increases maintenance costs associated
with corrective tasks not only for the direct corrective
costs (spare parts, labour hours) but also for the system
unavailability cost.
The maintenance policy aims to reduce the system
unavailability through the use of predictive or preventive
maintenance tasks for critical components. This policy
allows the reduction of unexpected failure occurrences
that cause the system unavailability and are usually very
expensive to repair.
In Nigeria, maintenance practices leave much to be
desired. Maintenance is generally regarded in Nigeria as
an undesirable cost generating activity rather than one
resulting in improved reliability, greater profitability and
higher productivity [9]. In Nigeria, maintenance is still
too often neglected and so the resulting associated costs
as a percentage of the total operational cost keep rising.
The most notable problem is the absence of an effective
and efficient maintenance strategy.
The investigation of Eti, et al. [10] showed that, main-
tenance cost, in the power industries in Nigeria amount
to approximately 23 - 35 percent of the total production
cost, that is much more than that for fuel.
The increasing electricity demand, the increasingly
competitive environment and the recent deregulation of
Nigeria’s electricity supply sector are resulting in in-
creased competition among the independent power pro-
ducers. To survive, suppliers must reduce maintenance
costs, prioritize maintenance actions and raise reliability.
Electric power projects in many countries, except Ni-
geria, are reliable; address specific customers’ require-
ments, and environmental compliance.
Failures in electric power stations result in downtime,
production losses and economic losses as well. Obvi-
ously, to achieve the global maintenance objective of
realizing high machinery availability at minimum cost,
adequate cognizance must be given to the element that
make up the cost, i.e. the cost of machine unavailability
and the cost of maintenance resources. Striking a balance
between these two costs to achieve the minimum total
cost creates an ideal maintenance situation. This should
be the objective of a good maintenance plan [11]. The
objective of this paper is to study on the effects of Pre-
ventive Maintenance Programme (PMP) implementation
at Egbin 1320 MW thermal power plant in Nigeria. The
paper aims to evaluate the reliability and availability of
the 6 × 220 MW steam turbine units installed in the
power station. The Egbin power plant is one of the larg-
est base generating power plants of the public power
company of Nigeria, the Power Holding Company of
Nigeria (PHCN).
2. Energy Crises in Nigeria
The quality of life of the citizens of in any country is
highly dependent on the availability of a reliable supply
of power. According to Chigbue [12], power as a major
component in the requirements for effective industriali-
Copyright © 2011 SciRes. EPE
zation and development is grossly inadequate in Nigeria.
For many years now, Nigeria has been facing an ex-
treme electricity shortage. This deficiency is multi-fac-
eted, with causes that are financial, structural, and socio-
political, none of which are mutually exclusive [13]. At
present, the power industry in Nigeria is beset by major
difficulties in the core areas of operation: generation,
transmission, distribution and marketing [14].
In spite of Nigeria’s huge resource endowment in en-
ergy and enormous investment in the provision of energy
infrastructure, the performance of the power sector has
remained poor, in comparison with other developing
economies [15]. This assertion was confirmed by a
World Bank [16] assessment study conducted on energy
development in Nigeria, which compared the perform-
ance of Nigeria’s power sector with those of 20 other
developing countries. The study reveals that the sector
had the highest percentage of system losses at 33 - 41
percent; the lowest generating capacity factor 20 percent;
the lowest average revenue at US$ 1.56 kWh; the lowest
rate of return at 8 per cent; and the longest average ac-
counts receivable period of 15 months.
There is no doubt that expensive and unreliable power
remains a major concern to all sectors of the economy in
Nigeria: the industrial, commercial, and domestic sectors
especially. Multiple and unpredictable power cuts, which
have become a daily occurrence in Nigeria, often result
in equipment malfunctioning, which make it difficult to
produce goods and provide service efficiently. As a re-
sult of this fundamental problem, industrial enterprises
have been compelled to install their own electricity gen-
eration and transmission equipment, thereby adding con-
siderably to their operating and capital costs.
Enweze [17] has estimated that about 25% of the total
investments in machinery and equipment by small firms,
and about 10% by large firms, were on power infrastruc-
ture. Despite the attempts by some firms to supplement
the power supply by PHCN, electricity demand by con-
sumers, particularly domestic users has continues to in-
Since inception of NEPA (renamed Power Holding
Company of Nigeria, PHCN in year 2004), the authority
has gradually increased its installed and generating ca-
pacity in an effort to meet the ever increasing demand.
Nevertheless, majority of Nigerians have no access to
electricity and the supply to those provided is not regular
[18]. According to Energy Policy report, from 2003, it is
estimated that the population connected to the grid sys-
tem is short of power supply over 60% of the time. The
electricity access in Nigeria is about 40% overall, al-
though it is much higher in the urban areas while it much
lower in the rural areas. On a fundamental level, there is
simply not enough electricity generated to support the
entire population in Nigeria.
3. Power Industry in Nigeria: Present State
The power sector is a critical infrastructure needed for
the economic, industrial, technological and social devel-
opment of Nigeria. Electricity consumption has become
one of the indices for measuring the standard of living of
a country. In Nigeria, power sector is presently being
managed by the Power Holding Company of Nigeria
(PHCN) as a vertically integrated utility comprising gen-
eration, transmission and distribution segments.
The national electricity grid presently consists of
fourteen generating stations (3 hydro and 11 thermal)
with a total installed capacity of about 8351.4 MW as
shown in Table 1. The Transmission network is made up
of 5000 km of 330 kv lines, 6000 km of 132 kV lines, 23
of 330/132 kV substations, with a combined capacity of
6000 MVA or 4600 MVA at a utilization factor of 80%.
In turn, the 91 of 132/33 kV substations have a combined
capacity of 7800 MVA or 5800 MVA at a utilization
factor of 75%. The Distribution sector is comprised of
23,753 km of 33 kV lines, 19,226 km of 11 kV lines, 679
of 33/11 kV substations. There are also 1790 distribution
transformer and 680 injection substations [19].
Although the installed capacity of the existing power
stations is 8351.4 MW, the maximum load ever achieved
was little above 4000 MW. Some of the power stations
generate less than 45% of their installed capacities. By
May, 2009 the average, generating capacity was about
2800 MW daily owning to corruption, political, grossly
inadequate funding and mismanagement reasons [20].
Currently, most of the generating units have broken
down due to limited available resources to carry out the
needed level of maintenance. Hence, the electricity net-
work has been characterized by constant system col-
lapses as a result of low generating capacity by the few
generating stations presently in service.
Repositioning of the power sector is a key stimulus to
the rapid industrialization of all key sectors of the
economy like manufacturing, telecommunications etc.
As it can be seen in Table 1, the existing plants operate
at far below their installed capacity as many of them
have units that need to be rehabilitated, retrofitted and
upgraded [21]. The percentage of generation capability
from hydro is 34.89%, from gas turbine 35.27% and
from steam turbine is 29.84%. The relative contributions
of hydro power stations from energy (MWh) standpoint
are higher than that of thermal power stations as opposed
to installed power (MW) standpoint.
Some of the reasons adduced for low power availabil-
ity include: gas pipelines vandalization resulting to in-
adequate gas supply by Nigrian Gas Company to most e
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Table 1. Summary of generation capabilities of PHCN power stations as operated in the year 2008 (Jan-Dec).
Plant Operator Age (Year) Type
No of
Current No
38 to 40
26 to 30
8 to 45
Total 8351.4 4176.24 0.50 93 45
Source: NCC Oshogbo.
thermal power plants, aged plants, outdated equipment
(generators, turbines, governors, transformers, and switch
gears). In addition to these, the transmission network is
radial and overloaded, and suffers from the following
constraints [20]:
Cannot wheel more than 4000 MW;
Has poor voltage profile in most of the network, es-
pecially in the North;
Inadequate dispatch and control infrastructure;
Radial and fragile grid;
Frequent system collapses
Higher transmission losses of 10% - 15%;
Limited national access to electricity of about 40%
for households, made up of 81% urban and 18% rural
Some of these constraints might be reduced or re-
moved by replacing many of the transformers, strength-
ening the transmission and distribution systems and up-
grading the switchgear.
For the past two decades, the power demand in Nige-
ria has been on the increase while available generating
capacity remained largely static or even showing a de-
creasing long-term trend. The consequence of this was to
load shed in order to ensure system stability (maintain
equilibrium between available generation and selective
The International Energy Institute’s comparative
analysis of the per capita consumption of electricity
worldwide (Table 2), underscores the stark reality of
Nigeria’s power sector. The comparative analysis shows
poor state of Nigeria’s power sector, compared with even
some of the countries that began as newly independent
countries in the 1960s. The challenge now is how reli-
able power supply can become accessible to majority of
Nigerians at an affordable price.
Manufacturers Association of Nigeria (MAN) gave the
following Comparative performance indicators shown in
Table 3. The data for some Southern Africa Develop-
ment Community (SADC) countries such as Botswana
and South Africa are comparable to those of USA and
France. The performance of the Nigerian power sector on
the International Best Practices comparative rating is
disgraceful cause for great concern. Perhaps, no other
sector feels it as much as the manufacturing/ industrial
sector wherein some notable international companies and
organizations are on self-generated electricity on 24
hours daily for the 365 days of each year, as confirmed
by a 2001 UNIDO. Survey showed that manufacturers
generated about 72% of total power required to run their
factories on the average.
The PHCN feeder reliability is extremely poor, with
figures like 120 faults per kilometer per year compared
to international best practice of 10 to 20.
4. Maintenance Problems in Nigeria Electric
Power Stations
Maintenance can be defined as all actions appropriate for
retaining an item/equipment in, or restoring it to a given
condition. More specifically, maintenance is used to re-
pair broken equipments, preserve equipment conditions
nd prevent their failure, which ultimately reduces pro- a
Copyright © 2011 SciRes. EPE
Table 2. Comparative analysis of the per capita consumption of electricity, world wide.
S/No Country Population (Million) Power Generation (MW) Per Capita Consumption (KW)
1 USA 250.0 813,000 3.2
2 CUBA 10.54 4000 0.38
3 UK 57.5 76,000 1.33
4 UKRAINE 49.0 54,000 1.33
5 IRAQ 23.6 10,000 0.42
6 SOUTH KOREA 47.0 52,000 1.09
7 EGYPT 67.9 18,000 0.265
8 TURKEY 72.0 12,000 0.16
9 SOUTH AFRICA 44.3 45,000 1.015
10 NIGERIA 140.0 4000 0.03
Table 3. Power supply reliability indices (international best practices).
1. System Average International Duration Index, SAIDI—Annual average total duration of power interruption to a consumer, in minutes.
USA Singapore France Nigeria (NEPA data) Nigeria (MAN study)
SAIDI min. 88 1.5 52 900 60,000
2. System Average Interruption Frequency Index. SAIFI—Average number of interruptions of supply that a consumer experiences annually.
SAIFI. No. per year 1.5 NA NA 5 600
3. Consumer Average Interruption Duration Index (CAIDI)—Average duration of an interruption of supply for a consumer who experiences the
interruption on an annual basis, in hours.
CAIDI. hr. Zero NA Zero 9 15
Average Service Availability Index (ASAI)Ratio of (consumer hours service availability)/consumer hours service demanded.
ASAI 1 1 1 NA 0.4
Source: Manufacturers’ Association of Nigeria presentation at EPSR Act Workshop, 2005.
duction loss and down time as well as the environmental
and associated safety hazards [22].
Maintenance activities in the Nigerian electric power
industry are at present largely reactive, i.e. ‘fire-fighting’,
to solve the problem, whatever it is, as quickly as possi-
ble and being in a state of readiness to deal with the next
outbreak whenever it happens. The problems are ex-
pected but not prevented. Indeed, the view within this
maintenance culture is that problems occur due to factors
beyond practical and resource control: It is accepted that
something will always go wrong and nothing much can
be done about it in advance. The occurrence of the prob-
lem is often coupled with reactive responses—once the
failures occur, the “fire-fighting” team is brought into
action. However, because little is done in such a culture
to anticipate problems or seek long-term solutions, the
whole exercise becomes repeated far more often than it
should be. Also, because the effort and resource go into
fire-fighting rather than prevention, faults occur. The
basic approach would be different in a culture of
long-term and continual improvement [9]. Comparisons
have been made of modern maintenance practices in the
more developed economics with that occurs in Nigeria.
Significant differences arise due to variations in corpo-
rate culture, pertinent learning opportunities and effec-
tiveness of strategic planning.
Efforts made by the Federal Government to improve
availability and reliability of the electric power supplies
in Nigeria have been frustrated by a lack of a corporate
culture in all facets of management in Nigeria. Achieving
the implementation of proactive maintenance, in any
Nigerian organization, requires a cultural transformation.
Commitment of the concerned individuals, a supportive
cultural environment and wise leadership are fundamen-
tal prerequisites for achieving high quality maintenance.
The training, fostering and competence building of the
managers themselves are crucial to a successful overall
quality maintenance programme.
Maintenance management in Nigeria still esteems
tough, individualistic, dominating leadership that often
fails to perceive threats or opportunities. More effective
management would be pivotal to organizing personnel to
recognize pertinent opportunities and achieve worthwhile
results rather than generate impasses, stagnation, bu-
reaucracy and wasteful interpersonal friction.
The following maintenance problems are frequently
encountered in Nigerian electric power stations:
Maintenance is not treated seriously at board level, or
even by local management;
Maintenance processes lack a business culture (e.g.
no business plans, ineffective or superficial budgets
and unfocused reports);
Maintenance technicians and even team leaders lack
adequate management skills;
Pre-occupation with introducing advanced mainte-
nance methods, while relevant basic maintenance
practices are not being implemented.
The Nigerian electric power industry still uses traditional
maintenance planning to compile maintenance schedules
for all equipment and plant. These schedules only rarely
reach the shop floor. Hence, maintenance schedule ends up
not being implemented.
5. Plant Condition and Maintenance
Attitude in Egbin Power Station
Egbin power plant is the largest generating plant in Ni-
geria and one of the largest in West African Sub-region.
The plant is located at the suburb of Lagos State, Ijede
area of Ikorodu. The plant was commissioned in 1985
and consists of 6 units of 220 (6 × 220 MW) (Reheat-
Regenerative). They are dual fired (gas and heavy oil)
system with modern control equipment, single reheat; six
stages regenerative feed heating. The overall cost of the
plant was US $ 1 billion with an expected life of 25 years.
The estimated life was based on the fact that the plant
should run mainly on natural gas which does not give the
serious boiler slag and ash problem characteristic of coal
fuel [23].
Natural gas is supplied to the plant directly from the
Nigerian Gas Company (NGC), Lagos operations de-
partment, Egbin gas station, which is annexed to the
thermal plant. Since Egbin thermal plant is located on the
shores of the lagoon cooling water for the plant’s con-
densers is pumped from the lagoon into the water treat-
ment plant en route to the condensers.The station has
been generating power far below installed capacity due
to maintenance problems. These problems have affected
the availability and reliability of the plant. Figure 1 and
Figure 1. Unit by unit energy generation in MWh.
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Figure 2 show the energy generated and running hours
of the plant from 2005 to 2009 respectively. The total
energy generated from 2005 to 2009 varies from
3,383,869 to 8,591,905 MWh, while the running hours
vary from 29,706.12 to 48,114.18 hrs. The highest total
energy generated of 8,591,905 MWh was obtained in
2005, and the highest running hours of the plant also
occurred in 2005. There has been a sharp declination in
total energy generation and running hours from 2005 to
2009. In order to improve the plant performance and to
minimize maintenance problems, there is need for effec-
tive maintenance scheduling which is a major determi-
nant of the productivity of the workforce.
From a recent survey, there is evidence that the power
station performs disappointingly compared with world-
class operations [24]. There is frequent occurrence of
breakdown of critical equipment. Also, overhauling op-
eration is not always carrying out as schedule due to de-
lay in release of fund. Turning around maintenance
(TAM) is not done regularly due to politics. Apart from
politics, due to small spare capacity available from gas
turbine plant (24 MW) and emergency diesel generator
(1.5 MW) which is not enough to be sent out, there is
always fear of power outage. This is because during an-
nual inspection, the plant has to be shut down for 30 or
40 days.
6. Results
Table 4 shows the data on units’ failures per year begin-
ning from the year 2005 to 2009 at Egbin thermal power
plant. Meanwhile, Table 5 shows the data on units’ out-
ages duration for the past five years. The types of faults
in the power plant can be categorized into 4 main groups:
plant fault, system fault, gas fault and operational fault.
Figure 3 shows the total number of failures in hours ac-
cording to the 4-main categories of faults from the year
2005 to 2009. Meanwhile, Figure 4 shows the total
number of overall time of plant outages in hours for all
the functional units. From Figure 1, the most occurring
fault is the plant fault. This is followed by gas fault. The
highest number of plant fault occurred in the year 2008
(2171.27 hr) and the minimum occurred in the year 2009
(1499.39 hr). In addition, Figure 1 shows that there are
relatively small numbers of operational faults within the
period considered.
From Figure 4, it can be seen that the total outages
from 2005 to 2009 are inconsistent, ranging from 3053.81
to 4811.29 hr. This shows that the trends of outages
hours are unpredictable from year to year. There are
many factors responsible for increasing and decreasing
trend in total outages hours. These factors may include:
difficulty to perform the maintenance activities, delay in
Figure 2. Unit by unit running hours.
Figure 3. Outages hours per year according to fault classification.
Figure 4. Total outages hours per year.
gas supply/gas limitation, shutdown due to failure of
some critical components (e.g. steam leakages, system
surge, system under-frequency, poor vacuum, super
heater leakage, boiler tube leakage etc.), delay in release
of fund for replacement of parts and repairs and the skills
of technicians or operators.
Copyright © 2011 SciRes. EPE
Table 4. Number of failures per year at Egbin thermal power
Number of Failure
2005 2006 2007 2008 2009
1 46 36 45 41 37
2 44 22 44 32 29
3 41 34 - 13 37
4 24 22 40 44 37
5 32 40 44 47 34
6 N/A N/A N/A N/A N/A
Table 5. Units outages duration (hr s) at Eg bin thermal power
Outages Duration (hrs)
2005 2006 2007 2008 2009
1 1093.18 722.31 3581.85 1521.06 1645.38
2 770.03 1780.71 1755.26 3151.67 479.17
3 738.60 1497.53 8123.28 6238.07 2344.11
4 634.20 1425.01 1602.97 1725.10 1686.22
5 1072.19 1093.37 2332.21 1457.98 1547.72
6 N/A N/A N/A N/A N/A
6.1. Evaluation of Availability and Reliability of
Egbin Power Plant
The availability and reliability analysis was based on the
available five units as at the time the data was collected.
As stated earlier, unit 6 is presently not functional. The
application of reliability and maintenance (R & M) prin-
ciple in Egbin thermal power station plants/equipment
requires that the system/component availability be de-
fined in terms of Mean-Time-between-Failures, MTBF
and Mean-Time-to-Repair, MTTR. MTBF is related to
the duration of outages. By definition, availability (A),
failure rate (λ), MTBF and MTTR are computed as:
1Total operating time
o of failures
 (1)
Total outage time1
MTTR No of failures
 (2)
When these two factors are known for any given sys-
tem or component, then the availability (A) is expressed
MTBF 1Uptime
MTBF MTTR1Uptime Downtime
 (3)
No of failurs between maintenance
Total operating time between maintenance
= failure rate i.e. number of failures/unit time
τ = duration of outage
µ = repair rate = 1
Reliability, R(t) = exp (t/MTBF) = exp(λt) (4)
here t = period of failure
aintainability (Mt) = exp (t/MTTR) = exp (µt) (5)
Utilization efficiency
Actual work hours
Max. potential hours of operationdelay hours
Figures 5 to 10 show the result of availability (A),
MTTR and MTBF at Egbin power plant.
6.2. Plant Availability
This section deals with analysis of the entire plant avail-
ability for the year 2009.
Total outages hrs/yr = 4147.02
Number of failures/yr = 174
MTTR = 4147.02/174 = 23.38 hrs
MTBF = 4612.98/174 = 26.51 hrs
Availability (A) = 26.51/50.31 = 0.527
Unavailability = 1 A = 1 0.527 = 0.473
Capacity factor = 1100/1320 = 0.833
The theoretical energy generation that could be ob-
tained from available power (1100 MW) if the plant
worked every second of the year non-stop is 1100 × 8760
= 9,636,000 MWh.
While the theoretical maximum energy that could be
attained from the installed power (1320 MW) if the plant
worked every second of the year non-stop is 1320 × 8760
= 11,563,200 MWh.
The actual total energy generated in 2009 is 3,383,869
Generation Utilization index = Actual generation/
Available capacity = 35.11%.
Capacity Utilization index = Available capacity/In-
stalled capacity = 29.26%.
7. Discussion
Analysis of the available data of Egbin thermal power
plant for the years 2005 to 2009 has been carried out and
the results for MBTF, MTTR and Availability (A) are
shown in Figures 6 to 10. The results of this study show
that the five units presently functional at the station are
not in good condition. This is because, the availability of
he units vary from 28.79 to 94.53 percent. t
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Figure 5. Variation of unit availability for each year.
Figure 6. Unit availability per year.
The availability of the plant is very low compare to
world class power industry. Figure 5 shows that Unit 3
has the lowest availability (28.79%) in the year 2008 and
unit 2 has the highest availability (94.53%) in 2009. Fig-
ure 6 shows variation in availability of each unit within
the period considered. The availability of unit 1 varies
from 0.5911(2007) to 0.9176 (2006), unit 2 varies from
0.6402 (2008) to 0.9453 (2009), unit 3 varies from 0.0
(2007) to 0.9157 (2005), unit 4 varies from 0.8031 (2008)
to 0.9276 (2005) and unit 5 varies from 0.7338 (2007) to
0.8776 (2005). This analysis shows that unit 4 has high-
est availability within the period considered. The mean
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Figure 7. Variation of unit MTTR for each year.
Figure 8. Unit MTTR per year.
time to repair (MTTR) ranges from 16.52 to 479.85
hours. Figures 7 and 8 show that Unit 3 has the highest
MTTR in 2008 and unit 2 has the lowest in 2009. This
shows that lot of time was spent on unit 3 in 2008 in or-
der to put it to operation. From this it can be concluded
that there is inverse relationship between the component/
equipment availability and failure rate. Figures 9 and 10
show the unit mean time between failures (MTBF) from
2005 to 2009. Unit 4 has the highest MTBF of 338.58 hrs
and 333.41 hrs in 2005 and 2006 respectively; unit 1 has
the lowest MTBF of 115.07 hrs in 2007. This shows di-
rect relation between MTBF and unit availability. As the
unit with highest MTBF has highest availability.
In general, considering the whole plant availability
with the available data for the year 2009, it was found
that the plant availability was 52.7 percent with capacity
factor of 0.833. The actual energy generation in 2009
was 3,383,869 MWh, while the estimated theoretical
energy generation that could be obtained from available
power (1100MW) if the plant worked every second of
year non-stop is 9,636,000 MWh. From the available
data on the plant, the major factors responsible for this
wide different between the actual energy generation and
theoretical energy generation in the year 2009 include
plant fault which caused 1499.39 outages hours. This
comes from shut down due t re-heater leakage, partial o
Copyright © 2011 SciRes. EPE
Figure 9. Variation of unit MTBF for each year.
Figure 10. Unit MTBF per year.
loss of flame, vacuum decay, super-heater tube leakage
etc. In addition to this, other fault is gas fault which
caused 1882.7 outages hours. This is as a result of dis-
ruption or shortage of gas supply to the plant. Due to this
fault, the affected unit has to be shut down until gas sup-
ply is restored. These two factors play major role in the
availability of thermal power plant.
The trend of power availability reflects how effec-
tively managed the station in terms of down time, spare
parts, availability of funds, pipeline vandalization etc.
Copyright © 2011 SciRes. EPE
8. Conclusions
The reliability of power plant unit is one of the most im-
portant performance parameters which reflect the quality
and standards. The great care and effort devoted to in-
creasing the reliability and quality of electrical power is
an indication of the economic implication for the power
This study has investigated the reliability and avail-
ability of Egbin power station units in relation to imple-
mentation of preventive maintenance programme. The
availability analysis shows different result for each unit
indicating differences in their system installation, main-
tenance and operation. As the availability of each unit
varies from 28.79% to 94.53% for the five years data
base considered. Also, the availability of the entire plant
for the year 2009 was computed as 52.7%, while the
generation utilization index is 35.11% and capacity
utilization index 29.26%.
The availability and reliability of the turbines pre-
sented in this study reflect on site behavior, including the
effects of changes in auxiliary systems maintenance pol-
icy. Identifying the effects of component failure on the
system under analysis, based on the failure effects classi-
fication, a maintenance policy can be formulated to re-
duce their occurrence probabilities.
Better aims and specific targets are needed for the Eg-
bin power station to improve maintenance management
systems and productivity. This should be based on a new
maintenance paradigm that will improve maintenance
control and PM activities.The managers must formulate
wise strategies, make decisions and monitor progress
against plans by collecting, retrieving and analyzing data.
To reduce downtime and achieve high production ca-
pabilities, the aim should be to find ways to increase
equipment reliability and extend the equipment’s life
through cost effective maintenance. To achieve these,
PHCN must move away from the traditional reactive
maintenance mode to proactive maintenance and man-
agement philosophies. There should be maintenance
processes that fully address Total Quality Maintenance
(TQM) and Total Productive Maintenance (TPM) oper-
ating modes. Such change requires a complete shift to a
Total Planned Quality Maintenance (TPQM) approach,
which is a maintenance and management philosophy that
advocates planning all maintenance (i.e. preventive, pre-
dictive and corrective), as well as the control of quality
in maintenance operations.
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