Chapter 3: Maintenance Management and Control

1
Chapter 3 Maintenance Management and Control

• Overview
• Effective Maintenance Programs
• Maintenance Project Control Methods

2
Effective Maintenance Programs

• Objectives improve plant availability, reduce
  cost, and improve equipment reliability and
  product quality
• Steps for managing a maintenance program
  effectively
• Identify existing deficiencies
• Set maintenance goals
• Establish priorities
• Establish performance measurement parameters
• Establish short and long-range plans
• Document plans and forward copies to all
  concerned individuals
• Implement plan
• Report status
• Examine progress frequently

3
Effective Maintenance Programs

• Planned Maintenance Program
• Convert most of the maintenance works into
  scheduled maintenance
• Tasks inspection, servicing of jobs,
  condition-based maintenance
• All activities are preplanned material planning
  and stocking
• Emergency Maintenance Program
• Should minimize and lt10 total maintenance works
• Handling emergency maintenance two
  approaches Add to regular schedule ?reserve
  10-15 capacity Estimate the amount of
  emergency?skilled workers
• Reliability Improvement Program
• Critical equipment history files ? MTBF
  ?frequency of emergency maintenance n/MTBF, n
  operation hours
• Another approach reliability-centered
  maintenance program (RCM) restore gtltbring to new

4
Effective Maintenance Programs

• Equipment Management Program
• Total Production Maintenance (TPM) ? equipment
  management ? improve product quality ? improve
  OEE
• Causes of equipment losses Failure Set
  up and adjustments Idling and minor
  stoppages Reduced speed Process
  defects Reduced yield

5
Effective Maintenance Program

• Cost Reduction Program
• Use engineering method approaches study how the
  work is being performed ? develop a better way
• Simplify and eliminate unnecessary steps
• Considered areas Alternative material and
  spare parts Alternative method for inspection
  and overhaul Alternative equipment and
  tools Alternative procedures for planning and
  scheduling Alternative job time standards
• Training and Employee Motivation Program
• on-the-job and off-the-job training ? upgrade,
  update

6
Maintenance Planning and Scheduling

• Almost all maintenance works (90) should be
  planned and scheduled. Only emergency work should
  be planned as it is processing
• Maintenance works classification
• Routine and preventive maintenance
• Emergency or breakdown maintenance
• Design modification
• Scheduled overhaul that involves the shutdown of
  the plant
• Others scheduled overhaul, repairs or building
  of equipment

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Scheduling Techniques

• Gantt Chart
• Mathematical Programming Approaches
• Integer Programming Approaches for Maintenance
  Scheduling
• Stochastic Programming Approaches for
  Maintenance Scheduling
• Network models
• Critical Path Method (CPM)
• Program Evaluation Review Technique (PERT)

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Gantt Chart
Critical Path Method

• CPM is suitable for large jobs overhaul,
  coordinate plant shutdown, turnaround
  maintenance)
• Procedure
• Step1 develop the project network diagram
• Step2 critical path calculation
• Step 3 determine minimum times for each job
• Step 4 Level the resources (use total float)

9
Network modelCritical Path Method

• Step1 develop the project network diagram
• an arc an activity (a job), the direction?he
  progress of the project
• a node an event a moment that specifies the
  start or completion of an activity
• each activity is represent by only one arc in
  the network
• No two activities can be represented by the same
  start and end nodes.In some case, the dummy
  activity with zero duration is created to adhere
  this rule

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Network modelCritical Path Method

• An activity is added to the network that secure
  the precedence relationships, if we can
  determine (i) the activities complete
  immediately before this activity (ii) the
  activities start immediately after this
  activity (iii) the activities occur
  simultaneously with this activity
• Activities originating from a certain node
  cannot start until the activities terminating at
  this node have been completed
• Step2 critical path calculation

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Network modelCritical Path Method

• Critical jobs are those that will cause a delay
  in the completion of the whole project if a delay
  in their starting time occurs
• A job (i,j) is non-critical if (LCj-ESi)gtDij
• Forward path calculate ESi maxESiDij, ? I
• Backward path LCj minLCj-Dij, ? j
• Where Dij is job(i,j) duration ES0
  Earliest start time at the beginning node (node
  0) LCnESn, latest completion time at the
  end node n
• An activity (i,j) lies on the critical path
  if ESjLCj ESjLCi ESj-ESiLCj-L
  CiDij

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Network modelCritical Path Method

• The final result of the CPM calculation should
  provide a schedule for all the activities that
  level the resources. The critical activities must
  be scheduled at their earliest start time. Each
  non-critical activity has two types of
  float TFij total float
  LCj-ESi-Dij FFij free float ESj
  ESi-Dij
• Develop time chart showing the schedules for all
  activities
• Step 3 Perform project crashing(determine
  minimum times for each job critical
  activities)
• Step 4 Level the resources (use total float)

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Example

• American Airlines needs to schedule 10 aircraft
  of various designs for maintenance. Based on
  flight records and the specific design of each
  aircraft, management has estimated that the
  amount of time required by maintenance works will
  be given in the following table (in days)
• Aircraft Time (days) Precedence
  relationship
• A 3 0
• B 4 0
• C 3 B
• D 6 C,A
• E 3 0
• F 3 E,D
• G 2 B
• H 4 F,G
• I 8 H
• J 2 I
• What is the estimated total elapsed time for
  maintaining all 10 aircraft?

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Network model Program Evaluation Review
Technique

• Program Evaluation Review Technique (PERT)
• PERT addresses the issue of uncertainty for the
  duration of activities
• The mean D and the variance V for the activity
  duration time is given by
• Where Oij Optimistic time Pij
  Pessimistic time mij Most likely time

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Network model Program Evaluation Review Technique

• Assume that the activities on the network are
  independent and let Xi be the occurrence time of
  node event i. Xi is the sum of independent
  random variables and is approximately normal
  with
• If the schedule of occurrence of node i is TSi,
  then where ? is
  the distribution function of the standard normal
  distribution