Maintenance Optimization Overview and Strategies
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Jørn Vatn
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Maintenance
The combination of all technical and administrative actions, including
supervision actions, intended to retain an item in, or restore to, a state in
which it can perform a required function
Preventive maintenance
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Corrective maintenance
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Maintenance optimization
Balancing the cost and benefit of maintenance
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Deciding the amount of preventive maintenance (i.e.
choosing maintenance intervals)
Deciding whether to do first line maintenance (on the cite),
or depot maintenance
Choosing the right number of spare parts in stock
Preparedness with respect to corrective maintenance
Time of renewal
Grouping of maintenance activities
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The bath
tub curve is a
basis for choosing
maintenance activities
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There are two such curves
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The
hazard rate
for ”local time”
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The
failure intensity
for ”global time”
•
Combining the two:
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The hazard
rate
for local time
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such as light bulbs in the signalling
system
. Methods are RCM and FMEA
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In this course we have main focus on preventive
maintenance (PM)
Maintenance optimization is thus more or less the same
as establishing an optimal maintenance program
Reliability Centred Maintenance (RCM) is often
considered to be the “best” approach in this context
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As the system deteriorates, traditional preventive maintenance
activities could not bring the system to a satisfactory state
Renewal of the entire system, or part of the system is required
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In this course we will present methods for optimum renewal strategies
based on LCC modelling
The following dimensions are included in the LCC model:
safety costs
punctuality costs
maintenance & operational costs
cost due to increased residual life length
project costs
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This effective failure rate is the failure rate we would
experience if we (preventive) maintain a component at a
given level
Notation:
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=
E
(
)
E
is the effective failure rate = expected number of failure per unit
time
is the maintenance interval
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There are two challenges
First we want to establish the relation
=
E
(
)
depending on the
(component) failure model we are working with
Next, we need to specify a cost model to optimise
The cost model will generally involve system models as fault tree
analysis, Markov analysis etc. This enables us to find the optimum
maintenance intervals in a two step procedure
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Component model
Effective failure rate is given by
=
E
(
) =
/100
is the maintenance interval
Total cost of a component failure
CM
Cost
= 10
Corrective maintenance cost including loss of production during
the repair period
Cost per preventive maintenance action carried
PM
Cost
= 1
The total cost per unit time
C
(
) = PM
Cos
t
/
+ CM
Cos
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E
(
) = 1
/
+
/10
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Graphical
MS Excel Solver
Analytical
Explore the concept of maintenance optimization, including definitions, scope, theory, and the importance of Preventive Maintenance and Reliability Centered Maintenance (RCM) in establishing an optimal maintenance program. Learn about balancing costs, decision-making for maintenance intervals, spare parts management, and more.
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Presentation Transcript
Introduction to the maintenance optimization J rn Vatn 1
Definitions Maintenance The combination of all technical and administrative actions, including supervision actions, intended to retain an item in, or restore to, a state in which it can perform a required function Preventive maintenance The maintenance carried out at predetermined intervals or according to prescribed criteria and intended to reduce the probability of failure or the degradation of the functioning of an item Corrective maintenance The maintenance carried out after fault recognition and intended to put an item into a state in which it can perform a required function Maintenance optimization Balancing the cost and benefit of maintenance 2
Scope of maintenance optimization Deciding the amount of preventive maintenance (i.e. choosing maintenance intervals) Deciding whether to do first line maintenance (on the cite), or depot maintenance Choosing the right number of spare parts in stock Preparedness with respect to corrective maintenance Time of renewal Grouping of maintenance activities 3
Maintenance theory Failure rate The bath tub curve is a basis for choosing maintenance activities Time There are two such curves The hazard ratefor local time The failure intensityfor global time Combining the two: 4
Performance loss The hazard rate for local time is appropriate for components such as light bulbs in the signalling system. Methods are RCM and FMEA Performance loss Failure intensity/ 1 Local time Local time Local time 4 3 2 Global (system) time Point replacement of sleepers is a mean to postpone the complete renewal of sleepers. JBV method=LCC. JBV method=LCC. Rail grinding is a maintenance activity to extend the life length of the rails. JBV method=LCC. Complete renewal will be required at some point of time. 5
Preventive maintenance and RCM In this course we have main focus on preventive maintenance (PM) Maintenance optimization is thus more or less the same as establishing an optimal maintenance program Reliability Centred Maintenance (RCM) is often considered to be the best approach in this context RCM is a systematic consideration of system functions, the way functions can fail, and a priority based consideration of safety and economics that identifies applicable and effective PM tasks 6
Renewal and Life Cycle Cost As the system deteriorates, traditional preventive maintenance activities could not bring the system to a satisfactory state Renewal of the entire system, or part of the system is required The cost of renewal is often very large we need formalised methods to determine when to perform renewal In this course we will present methods for optimum renewal strategies based on LCC modelling The following dimensions are included in the LCC model: safety costs punctuality costs maintenance & operational costs cost due to increased residual life length project costs 7
Effective failure rate This effective failure rate is the failure rate we would experience if we (preventive) maintain a component at a given level Notation: E = E( ) E is the effective failure rate = expected number of failure per unit time is the maintenance interval 8
Effective failure rate and optimization There are two challenges First we want to establish the relation = E( ) depending on the (component) failure model we are working with Next, we need to specify a cost model to optimise The cost model will generally involve system models as fault tree analysis, Markov analysis etc. This enables us to find the optimum maintenance intervals in a two step procedure 9
Introductory example Component model Effective failure rate is given by = E( ) = /100 is the maintenance interval Total cost of a component failure CMCost = 10 Corrective maintenance cost including loss of production during the repair period Cost per preventive maintenance action carried PMCost = 1 The total cost per unit time C( ) = PMCost / + CMCost E( ) = 1 / + /10 10
Solutions Graphical MS Excel Solver Analytical 11
