4. REACTIVE MAINTENANCE
Reactive Maintenance is also referred to as
breakdown, repair, fix-when-fail, or run-to-
failure (RTF) maintenance.
When applying this maintenance technique,
maintenance, equipment repair, or
replacement occurs only when the
deterioration in the condition of the equipment
causes a functional failure.
5. PREVENTIVE MAINTENACE
One of the underlying assumptions of maintenance
theory has always been that there is a fundamental
cause-and-effect relationship between scheduled
maintenance and operating reliability.
This assumption was based on the intuitive belief that
because mechanical parts wear out.
For example, a common practice has been to replace
or renew bearings after a specified number of
operating hours, assuming that bearing failure rate
increases with time in service.
6. PREDICTIVE MAINTENANCE
Predictive maintenance or condition monitoring, uses
primarily non intrusive testing techniques, visual
inspection, and performance data to assess
machinery condition.
Condition monitoring replaces arbitrarily timed
maintenance tasks with maintenance that is
scheduled only when warranted by equipment
condition.
Continuing analysis of equipment condition-monitoring data
allows planning and scheduling of maintenance or repairs in
advance of catastrophic and functional failure.
10. PROACTIVE MAINTENANCE
Proactive is the opposite of Reactive.
Proactive maintenance is an activity performed to
detect and correct causes of failure i.e. actions
taken to correct conditions that could lead to
material degradation.
Instead of investigating material and performance
degradation factors to determine the extent of
incipient and impending failure conditions, proactive
maintenance concentrates on identifying and
correcting abnormal causes of failure that create
unstable operating conditions.
11. HISTORICAL EVOLUTION OF
RELIABILITY CENTRED MAINTENACE
In the case of aircraft it was also
commonly assumed that all reliability
problems were directly related to
operating safety.
Over the years, However, it was found that
many types of failures could not be
prevented no matter how intensive the
maintenance activities.
12. INTERODUCTION TO
RELIABILITY CENTRED MAINTENANCE
While many industrial organizations were
expanding PM efforts to nearly all other assets,
the airline industry, led by the efforts of Nowlan
and Heap, took a different approach and
developed a maintenance process based on
system functions, consequence of failure, and
failure modes.
Their work led to the development of Reliability-
Centered Maintenance, first published in 1978.
13. RELIABILITY BASED MAINTENANCE
Reliability-Centered Maintenance (RCM)-
integrates Preventive Maintenance (PM),
Predictive maintenance and Proactive
Maintenance to increase the probability that a
machine or component will function in the
required manner over its design life-cycle with
a minimum amount of maintenance and
downtime.
14. RELIABILITY CENTRED MAINTENANCE
HIERACHY
RELIABILITY
CENTRED
MAINTENANCE
REACTIVE PROACTIVE
MAINTENANCE MAINTENANCE
*Small item *Root cause failure analysis
*Non critical PREVENTIVE PREDICTVE *Age exploration
*Unlikely to fail MAINTENANCE MAINTENANCE *FMEA
*Redundant
*Subject to wear out *Not subject to wear out
*Known failure pattern *Random failure
*Consumable *PM induced failure
15. OBJECTIVE OF RCM
To ensure realization of the inherent safety and
reliability levels of the equipment.
To restore the equipment to these inherent levels
when deterioration occurs.
To obtain the information necessary for design
improvement of those items where their inherent
reliability proves to be inadequate.
To accomplish these goals at a minimum total cost,
including maintenance costs, support costs, and
economic consequences of operational failures.
16. RCM PRINCIPLES
Reliability-Centered: RCM treats failure
statistics in an actuarial manner. The
relationship between operating age and the
failures experienced is important. RCM is not
overly concerned with simple failure rate; it
seeks to know the conditional probability of
failure at specific ages .
17. RCM PRINCIPLES
Acknowledges Design Limitations:
The objective of RCM is to maintain the inherent
reliability of the equipment design, recognizing
that changes in inherent reliability are the
province of design rather than maintenance.
Maintenance can only achieve and maintain the
level of reliability for equipment which is provided
for by design. RCM recognizes that maintenance
feedback can improve on the original design.
19. RCM PRINCIPLES
Function-Oriented:
RCM seeks to preserve
system or equipment
function, not just
operability for
operability's sake.
Redundancy of function
through redundant
equipment improves
functional reliability but EXAMPLE-REDUNDANT
increases life-cycle cost UPS DESIGN
in terms of procurement
and operating costs.
20. RCM PRINCIPLES
Tasks Must Be Applicable: Tasks must
address the failure mode and consider the
failure mode characteristics.
System-Focused: RCM is more
concerned with in maintaining system
function than individual component
function.
21. RCM PRINCIPLES
Logic Tree to Screen
Maintenance Tasks:
This provides a
consistent approach to
the maintenance of all
equipment.
22. RCM PRINCIPLES
Safety, Security, and Economics: Safety
and security must be ensured at any cost; life-
cycle cost-effectiveness is a tertiary criterion.
Failure as Any Unsatisfactory Condition:
Failure may be either a loss of function
(operation ceases) or a loss of acceptable
quality (operation continues).
23. RCM ANALYSIS
RCM analysis carefully considers the following
questions:
What does the system or equipment do; what are
its functions?
What functional failures are likely to occur?
What are the likely consequences of these
functional failures?
What can be done to reduce the probability of the
failure, identify the onset of failure, or reduce the
consequences of the failure?
24. BENEFIT OF RCM
To avoid loss of life, property damage, and
environmental harm,
The cost of repair decreases as failures are
prevented .
RCM places great emphasis on improving equipment
reliability.
A principal advantage of RCM is that it obtains the
maximum use from equipment. With RCM, equipment
replacement is based on actual equipment condition
rather than a predetermined, generic length of life.
25. RELIABILITY CENTRED MAINTENANCE
Advantages
Efficient.
Increased system reliability.
Lowered costs due to no unnecessary maintenance.
Minimized overhauls.
Reduced sudden equipment failures.
Maintenance focused on critical components.
Incorporates root cause analysis.
Disadvantages
Significant initial costs for training, and equipment.
Savings potential not readily seen by management.
26. RCM –Cost of maintenance and repair
Due to the initial investment required for obtaining the
technological tools, training, and equipment condition
baselines, a new RCM Program typically results in an
increase in maintenance costs.
This increase is relatively short-lived, averaging two to
three years. The cost of repair decreases as failures
are prevented and preventive maintenance tasks are
replaced by condition monitoring.
The net effect is a reduction of both repair and total
maintenance costs.
Often energy savings are also realized from the use of
condition monitoring techniques.
28. Cost of Maintenance Programs (Piotrowski 2001)
(in $per horse power per year)
18 $18
16
14 $13
12
REACTIVE
10 $9 PREVENTIVE
8 $6 PREDICTIVE
6 RCM
4
2
0
29. RCM AND FAILURE ANALYSIS
Failure is the cessation of proper function or
performance.
RCM examines failure at several levels: the system
level, subsystem level, component level, and the
parts level.
The goal of an effective maintenance organization is
to provide the required system performance at the
lowest cost.
This means that the maintenance approach must be
based upon a clear understanding of failure at each
of the system levels.
30. CAUSES OF FAILURE
The cause of a failure mode is a deficiency that
results in the failure mode.
A failure mode can be caused by one or more of the
individual components or by:
• Inadequate component design
• Improper installation or maintenance
• Improper selection of component parts
• Improper use of processes
• Inadequate control procedures
It is imperative that the focus in performing the FMEA
should be to identify all potential failure .
31. FAILURE MODES AND EFFECTS ANALYSIS
Failure Modes and Effects Analysis (FMEA) is
applied to each system, subsystem, and component
identified in the boundary definition.
For every function identified, there can be multiple
failure modes.
The FMEA addresses each system function, all
possible failures, and the dominant failure modes
associated with each failure.
The FMEA then examines the consequences of
failure to determine what effect failure has on
operation, on the system, and on the machine.
32. INTERPRETING THE FMEA
The FMEA is done to identify and/or eliminate
deficiencies and therefore eliminate or at least
minimize failure rate.
The traditional way to interpret the results of
the FMEA is to calculate the Risk Prioritization
Number (RPN) or Criticality/Severity
Categories.
33. Risk Priority Number (RPN)
or Criticality/Severity Categories
This number is the product of severity, frequency
and detection.
The RPN defines the priority of the failure. On its
own the RPNs has no value or meaning. It is only
used to rank (define) the potential deficiencies.
A goal of FMEA is to reduce the RPN or
Criticality/Severity Categories
The severity can be reduced through a change in
design, configuration and/or through a change in
how it is operated
34. Risk Priority Number (RPN)
or Criticality/Severity Categories
EFFECT RANKING CRITERIA
none 1 Results in no loss of function, reliability , safety margin,
health, environment or mission.
Very slight 2 Very slight reduction in performance and integrity.
Repair to failure can be accomplished during trouble call
slight 3 Slight reduction in performance .repair to failure may
be longer than trouble call .
Minor 4 Minor reduction in current performance. some portion
of mission may need to be rework or process delay.
moderate 5 Moderate disruption to facility function .100% of
mission may need to be reworked or process delay
significant 6 Significant disruption to facility function .some portion
of mission is lost. Delay in restoring function.
major 7 High disruption to facility function .some portion of
mission is lost. Delay in restoring function.
extreme 8 High disruption to facility function .significant delay in
restoring function.
serious 9 Potential safety ,health or environment issue .failure
will occur with warning.
hazardous 10 Potential safety, health or environment issue .failure
will occur without warning.
35. HOW TO INITIATE RCM
1.Develop a Master equipment list identifying the equipment in your
facility.
2.Prioritize the listed components based on importance or criticality to
operation, process .Assign components into logical groupings.
3.Types of Maintenance Programs
4.Determine the type and number of maintenance activities required and
periodicity using:
a. Manufacturer technical manuals .
b. Machinery history .
c. Root cause analysis findings - Why did it fail?
d. Good engineering judgment .
5.Assess the size of maintenance staff & Identify tasks that may be
performed by operations maintenance personnel.
6.Analyze equipment failure modes and impacts on components and
systems.
7.Identify effective maintenance tasks or mitigation strategies.
36. Transition to RCM -A case study
Some plants are turning to reliability-centered maintenance
(RCM) ,However, appropriate use of RCM creates increased
demands for testing (e.g., non-destructive evaluation), data
collection, and analysis.
The lack of such data collection and analysis appears to have
been a problem in the electricity distribution outages in Chicago
in summer 1999.
In reviewing those outages, the Department of Energy Power
Outage Study Team (2000) USA, noted that :
“Many fixed, periodic, substation maintenance programs had been
scaled back or discontinued in transition to a „reliability-centered
maintenance‟ philosophy. However, the collection of data and
measurements necessary for successful reliability-centered
maintenance was not fully in place.” As a result, “the ability to predict
possible component failures from the inspections that were performed
and data that were collected was limited.”
37. Principles of Maintainability Design
Great maintenance procedures cannot
overcome poor equipment design.
Special tools are rarely available when
maintainers need them, so design all
maintenance tasks to eliminate the need for
special tools.
