This document summarizes an article from the International Journal of Mechanical Engineering and Technology that implements Reliability Centered Maintenance (RCM) on an air compressor unit. It begins with an overview of RCM methodology and a literature review on previous RCM studies. It then details the 7 steps of RCM analysis conducted on the air compressor unit which includes failure mode analysis, criticality assessment, and development of a new preventative maintenance schedule. Cost analysis found the new RCM-based schedule reduces preventative maintenance costs by 15.57% annually. The conclusions state RCM provides an effective maintenance approach to minimize maintenance-induced failures and optimize preventative maintenance activities and costs.

1. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
INTERNATIONAL JOURNAL OF MECHANICAL ENGINEERING
6340(Print), ISSN 0976 – 6359(Online) Volume 5, Issue 1, January (2014), © IAEME
AND TECHNOLOGY (IJMET)
ISSN 0976 – 6340 (Print)
ISSN 0976 – 6359 (Online)
Volume 5, Issue 1, January (2014), pp. 26-32
© IAEME: www.iaeme.com/ijmet.asp
Journal Impact Factor (2013): 5.7731 (Calculated by GISI)
www.jifactor.com
IJMET
©IAEME
IMPLEMENTATION OF RELIABILITY CENTERED MAINTENANCE IN
AIR COMPRESSOR UNIT
Vivek S. Narnaware1, Ganesh D.Gosavi2, Pravin V. Jadhav3,
Rahul D. Gorle4
1,2,4
(Mechanical Engg., Department, Dr. Babasaheb Ambedkar College of Engg. and Research,
WanadongriHingna Road Nagpur/RTMNU Nagpur, India)
3
(Mechanical Engg., Department, Priyadarshini College of Engg., Hingna Road Nagpur/RTMNU
Nagpur, India)
ABSTRACT
Today’s maintenance programs are suffered from many drawbacks. Some équipements get
too little, while some gets too much préventive maintenance than required. Reliability centered
maintenance approach is found to be successful technique for solving such complex management
orientated problems regarding the maintenance. Reliability centered maintenance (RCM) is the
qualitative technique for developing the optimal preventative maintenance program which ensures
relability of machine opération. It focuses on the system, system function, functional failure, system
failure effect, their occurrences and criticality. Failure data analysis plays an important rôle to take
décision on maintenance planning. It is important to identify the occurrences of failure and
probability of failure for ranking the failure paths. It gives information about area of concentration in
maintenance activities. This paper includes RCM principles and methodology to understand RCM is
carried out in the plant or a system. The case study has been conducted at MSEB Thermal Power
Plant Khaperkheda Nagpur. An air compressor unit is selected for opération. The selection is based
on the breakdown failures record of past 18 months. RCM methodology are applied an system failure
analysis is done. Preventative maintenance shedule for RCM is prepared and it is compared with the
plant maintenance schedule.
Keywords: Functional Failure, Failure Analysis, FMEA, RCM, RTF.
1. INTRODUCTION
Air compressor unit plays an important role in thermal power plant. It supplies compressed
instrument air and service air to the plant. It consists of various components, proper working of
which ensures the functions of the compressor unit. While studying the failure record of the
26

2. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 5, Issue 1, January (2014), © IAEME
components, it is observed that some of them are frequently fail during the operation, some fail to
work earlier than predicted. Moreover failures of such components cause the shutdown of the
compressor unit and hence affect the working of the overall plant. The maintenance schedule of the
company mainly focuses on the daily breaking failures and an overhauling during year. Therefore
this work aims to generate proper maintenance planning and scheduling for the compressor unit that
based on the RCM technique for the air compressor unit components. Reliability centered
maintenance (RCM) is the qualitative technique for developing the optimal preventive maintenance
program which will ensure inherit ant reliability of machine operation. RCM can be defined as a
process or method used in structured way to determine the most effective approach of preventive
maintenance of equipment in its operating condition after proper evaluation of failure consequence.
It focuses on the system, function, functional failure, dominant failure effect, their occurrences and
critically. RCM philosophy employs preventive maintenance, predictive maintenance (PDM), time
directed (TD), condition directed (CD), failure finding (FF) and run-to-failure (RTF) maintenance
techniques in an integrated manner to increase the probability that a machine or component will
function in the required manner over its design life cycle with a minimum of maintenance. This
paper contains the RCM methodology and its implementation in an air compressor unit, key points in
RCM maintenance plan.
2. LITERATURE REVIEW
Study made by Islam H. Afefy
The results of the RCM technique applied of the plant show that the PM proposed tasks and
planning are generated. Moreover, PM is consisted of on-condition and scheduled maintenance. The
Run-To-Failure (RTF) frequency has been decreased. It is recommended to perform these tasks (CD,
TD and FF) every yearly, six monthly and monthly.
Study made by Katharina Fischer, Francois Besnard and LinaBertling
A Reliability-Centred Maintenance analysis of the two wind turbine models V44-600kW and
V90-2MW has been carried out. The analysis forms the basis for the development of quantitative
models for maintenance strategy selection and optimization. The mathematical models for
maintenance strategy selection and optimization that are being developed based on the presented
RCM study aim at contributing to this process. It is concluded to be an important step in order to
enhance the reliability, availability and profitability of wind turbines.
Study made by Salman T. Al-Mishari, and S. M. A. Suliman
The potential losses due to missing any element of the DMAIC process are very significant.
Assessment of contributing factors is often based on very subjective judgment. Shifts and drifts often
occur. The work reported in this paper attempts to illustrate the potential losses of missing these
important elements through a real example.
Study made by RizauddinRamli and Mohammad NizamArffin
RCM implementation in the PM activities at automotive manufacturing plant. The RCM has
been used to analyze and perform a decision making process in which maintenance strategy needs to
be chosen depends on the criticality of the equipment to the organization.
3. RESEARCH METHODOLOGY
This methodology will provide a comprehensive description of seven steps that have been
developed to systematically delineate the required information.
27

3. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 5, Issue 1, January (2014), © IAEME
Step 1:
Step 2:
Step 3:
Step 4:
Step 5:
Step 6:
Step 7:
System Selection & Information Collection
System boundary definition.
System description & functional block diagram.
System functions & functional failures.
Failure mode & effect analysis (FMEA)
Criticality & Probability of occurrences.
Task Selection.
Satisfactory completion of these seven steps will provide the preferred PM tasks. Failures in
air compressor unit is selected for the RCM study and the relevant information is collected from the
company. The functional block diagram for system is shown in fig.1.
Failure mode and effect analysis (FMEA) for different subsystems are done then the
criticality and probability of occurrences for the various failures are calculated and categorized in
four groups as shown in table no. 3. RCM task is selected. In this step the preventive maintenance
schedule based on reliability centered maintenance is made and compression between previous PM
& RCM based maintenance is done.
To
Plant
Power Atmospheric
Supply Air
Air suction
& delivery
system
(Compress
or
Subsystem)
Water
Supply
Pressurized
Air
Suction
&
Delivery
Pressur
I/II
Pressurized
Hot Air
Cooling
Water
system
Cool
Oil
Pressure
Gauge
High Pressure
Air
Air
Receiver
system
Cool
Air
Service
Air
Moisture
Contained
Air
Dry
Air
system
Air
Water Water
Pressure Temp
Status
Status
Pressure
Gauge
Fig. 1: Functional Block Diagram
28
Air
Heating
Silica
Filtration
Alumina
Particles
Heating

4. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 5, Issue 1, January (2014), © IAEME
Table 1 and table 2 shows the predicted RCM schedule and comparison with the previous
maintenance schedule.
RCM Schedule:
Sub assembly
Effect
Based task Description
Moderate Cost, very
high failure rate
1.Inspect chock up of valve
component.
2.Inspect
fracture
components.
3.Periodic cleaning of a Air
suction filter.
4.Replace of lapping.
F.F. (Monthly)
Piston ring
Moderate cost, high
failure rate
C. D. (6 months)
Guide ring
Moderate Cost, high
failure rate
Other
piston
assembly parts
Low failure
very high cost
rate
3.Unloader
assembly
4.Main Bearing
‘O’
ring
unloader
Bearing seized
low
low
Check during overhand
T.D. (12 months)
5.Lubrication
system
i. Oil level trapping
ii.
Oil
leakage
gaskets
iii. ‘O’ ring for oil
filter
Belt
Low
cost,
failure
High
cost,
failure
Low
cost,
failure
1.Check for suction pressure
high low
2.Check for suction pressure
high, low.
3. Check for piston ring
every 6 months
1.Check for suction pressure
high low.
2.Check for piston ring
every 6 months.
1.Keep one H.P./L.P. piston
assembled with guide rings.
2.Check guide ring every 6
month
Replace when fail
low
Check for oil level replace
failure parts
RTF
1.Air suction
delivery valve
&
2.Piston Ring Road
assembly
6.Belt
7.NRV
8.Packing
9.Suction filter
10.Cooling system
Component /
failure mode
Valve components
for
High cost, moderate
failure
NRV seat
NRV plate
NRV spring
NRV holder
1.Oil seal (3 piece &
6 piece packing,
pressure breaker)
Low
cost,
failure
2.Thrust washer ‘O’
ring sealing ring
All suction filter
Low
cost,
low
failure
Moderate cost, low
failure
Moderate
cost,
Moderate failure
‘O’ ring for I/C
‘O’ ring for A/C
Water
leakage
gasket
Moderate
Moderate
rate
low
cost,
failure
i.
C.D. (6 months)
T.D. (12 months)
RTF
Tighting
of
belts
ii.
Keep match
sets of belts
Replace failure parts
C.D. (3 months)
Check within 3 months
RTF
Replace failure parts
C.D. (monthly)
1.Cleaning of suction filter
2.relace
1.Acid cleaning
2.Use clean (filtered) water
for cooling system
3.Use of strainer for
filtration
C.D. (12 months)
Table 1: RCM Schedule
29
Frequency
C.D.(Condition of
belts)
RTF

5. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 5, Issue 1, January (2014), © IAEME
TASK COMPARISON
Component /
Failure mode
1.Valve
Components
Previous Preventive
Maintenance
Air suction filter cleaning
Cleaning of Valves /
servicing
2.Piston ring rod Piston ring, Guide ring
assembly
Replace
3.Connecting
Check of piston
rod, crosshead
assembly
4.Unloader
Check unloader parts
5.Bearing seized Bearing Check
6.Lub system
Oil filter cleaning
7.Belt
Belt tightening
Frequency
12 months
12 months
3 months
3 months
RTF
Check
RTF
Replace
tightening
8.NRV
9.Packing
Repalce fractured part
Check of packing part
12 months
3 months
10.Cooling
system
11.Oil
replacement
All coolers
Cleaning
Replace
12 months
RTF
Check of
packing parts
All coolers &
Jacket Cleaning
Oil sample test
in
&
3 months
6 months
12 months
Jacket
12 months
RCM
maintenance
Air filter
cleaning
Frequency
Piston ring guide
ring Check
Check
6 months
Monthly
2 months
---12 months
--C.D.
(Condition
monitory)
--3 months
12 months
3 months
Table 2 : Task Comparison
COST ANALYSIS
Ex- Salary given to the skilled labour, wages given to the semiskilled labour. In this study the Spare,
Consumable and manpower costs are calculated (refer tables A1 to A13) as follows :I)
Spares cost
= Rs. 3,66,342 /-
II)
Consumables coot
= Rs. 5691 /-
III)
Manpower cost
= 25,975 X 18 = Rs. 4,67,550 /-
IV)
Total breakdown cost
= 3,66,342 + 5691 + 4,67,550
= Rs. 8,39,583 /-
RCM COST ANALYSIS
In RCM cost analysis first predicted RCM failures are calculated and on this basis predicted
material cost is calculated (Refer tables A14 and A15).Failures have been categorized on the basis of
failure history. Prepared maintenance schedule leads to saving in maintenance cost in each category.
30

6. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 5, Issue 1, January (2014), © IAEME
Failure
Expected
Rank
Saving
Greater than 50
A
30%
Between 30 to 50
B
25%
Between 15 to 29
C
20%
Between 5 to 14
D
10%
Less than 5
E
RTF
Table 3 : RCM expected saving
No. of failures
Results obtained from RCM cost analysis are as follows :
Predicted RCM material cost = 2,99,961 /Reliability Centered Maintenance process is expected 90% savings in overtime cost.
Predicted RCM manpower cost = Previous Manpower cost – overtime cost (90% of
Previous)
Previous Manpower cost = Rs. 4,67,550 /Overtime cost
= 0.90 x 65250
= Rs. 6525 /Total Predicted RCM cost = Predicted RCM material cost + Predicted RCM manpower cost
= 2,99,961 + 4,08,825
= Rs. 7,08,825 /Reduction in Preventive Maintenance Cost = Previous Pm cost – Predicted RCM cost
= 8,39,583 – 7,08,825
= Rs. 1,30,797 /% Reduction in Preventive maintenance cost = (Reduction in P.M. cost / Previous P.M. cost) x 100 %
= (1,30.797 / 8,39,583) x 100%
= 15.57 %
4. RESULTS
RCM maintenance schedule results in the overall saving of 15.57% of existing maintenance
cost. Hence annual saving of Rs. 1,30,797 /- is expected.
5. CONCLUSIONS
RCM Maintenance scheduled is prepared and compared with the existing Maintenance
schedule. After comparison following points are observed.
Air suction filter should be cleaned monthly. It will prevent the dust dirt chock up the valve
parts so that failure rate will minimize.
Lubrication oil sample (servo system 68) should be tested periodically in Laboratory so that the
strategy for oil replacement can be made.
Water strainer should be provided for filtering the raw water. It will prevent the failures in the
cooling system.
Valve replacement should be done instead of valve lapping. It will improve the availability of
the air compressor Lapping process may be done in free time. It will minimize the labour time.
RCM program typically results in short term increase in maintenance costs. This increase is
31

7. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 5, Issue 1, January (2014), © IAEME
relatively short-lived. It will minimize the repair cost. Failures have been categorized on the
basis of failure history.
Prepared maintenance scheduled leads to saving in maintenance cost in each category. It is
concluded that Reliability Centered Maintenance is sample & effective maintenance ensuring
all through that maintenance induced failures are either eliminated or minimized. It does not
required complex numerical calculation. It re-examines the validity of previous preventive
maintenance schedule and develops cost effective preventive maintenance schedule. It predicts
spare parts inventories & risk maintenance decision for the system or plant.
6. REFERENCES
1. Islam H. Afefy, Reliability-Centered Maintenance Methodology and Application: A Case
Study, scientific research publication, Engineering, 2010, 2, 863-873.
2. Katharina Fischer, Francois Besnard, and LinaBertling, "Reliability-Centered Maintenance
for Wind Turbines Based on Statistical Analysis and Practical Experience," IEEE
Transactions on Energy Conversion,, vol.PP, no.99, pp.1-12.
3. Salman T. Al-Mishari, and S. M. A. Suliman, Sensitivity Analysis of Six-Sigma Applied to a,
Reliability Project. International Journal of Mechanical & Mechatronics Engineering
IJMME-IJENS Vol: 11 No: 03.
4. RizauddinRamli and Mohammad NizamArffin, Reliability Centered Maintenance in
Schedule Improvement of Automotive Assembly Industry, American Journal of Applied
Sciences 9 (8): 1232-1236, 2012.
5. A.Mariajayaprakash, Dr.T.Senthilvelan and K.P.Vivekananthan, “Optimisation of Shock
Absorber Parameters using Failure Mode and Effect Analysis and Taguchi Method”,
International Journal of Mechanical Engineering & Technology (IJMET), Volume 3, Issue 2,
2012, pp. 328 - 345, ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359.
6. Pravin Kumar.S, Venkatakrishnan.R and Vignesh Babu.S, “Process Failure Mode and Effect
Analysis on End Milling Process- A Critical Study”, International Journal of Mechanical
Engineering & Technology (IJMET), Volume 4, Issue 5, 2013, pp. 191 - 199, ISSN Print:
0976 – 6340, ISSN Online: 0976 – 6359.
7. N. Rishi Kanth, Dr.C.V.Mohan Rao and G. Yedukondalu, “New Method in Predictive
Maintenance of a Machine”, International Journal of Mechanical Engineering & Technology
(IJMET), Volume 3, Issue 1, 2012, pp. 142 - 149, ISSN Print: 0976 – 6340, ISSN Online:
0976 – 6359.
8. J. Arun, S. Pravin Kumar, M. Venkatesh and A.S. Giridharan, “A Detailed Study on Process
Failure Mode and Effect Analysis of Punching Process”, International Journal of Industrial
Engineering Research and Development (IJIERD), Volume 4, Issue 3, 2013, pp. 1 - 12,
ISSN Online: 0976 - 6979, ISSN Print: 0976 – 6987,
Books
1. Anthony M. Smith P.E., “Reliability –Centered Maintenance”, McGraw-Hill Publications
New Delhi.
2. Richard B.Jones “Risk based management a reliability centered approach “, Jaico Publishing
House New Delhi-1997.
3. P.K.Kalra, “Reliability, availability & maintainability (RAM) Engineering in Manufacturing
Vol 1.” Allied publishers Ltd, New Delhi (1997).
32