Chapter 4:Preventive Maintenance: Conceptual Frameworks

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Chapter 4Preventive Maintenance Conceptual
Frameworks

• Overview
• Preventive Maintenance
• Diagnostic Technologies
• Elements of Planned Maintenance

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Preventive Maintenance

• Preventive maintenance is a series of preplanned
  tasks performed to counteract known causes of
  potential failures of facility, equipment,
  systems functions
• Repair maintenance is considered as the
  replacement, refurbishment, or overhaul of the
  components in an equipment of system to make it
  capable of performing its intended function

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Preventive Maintenance

• Benefit of preventive maintenance
• Prevent premature failure and reduce its
  frequency
• Reduce the severity of failure and mitigate its
  consequences
• Provide warning of an impending or incipient
  failure to allow planned repair
• Reduce overall cost of asset management
• Repair Maintenance Classification
• Planned repair resources have been
  preplanned the work perform according to a
  set schedule
• Unplanned repair does not have preplanned and
  prescheduled criteria

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Work distribution
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Preventive Maintenance

• Objective of preventive maintenance is to
  maximize equipment availability and reliability
• Equipment availability probability of a piece of
  equipment being able to operate whenever needed
• Equipment reliability the probability that the
  equipment will be functioning at time t
• Well-designed equipment Maintainability
  probability of its being repaired/maintained
  during a specified time.

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Preventive Maintenance

• Categories of preventive maintenance
• Condition based Off line On
  line
• Statistically and reliability based Time
  based Use based
• PM can be planned and scheduled based on time,
  use or equipment condition

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Preventive Maintenance

• Failure mechanism of the equipment ? what
  task?
• Time based (dominant failure mechanism) ?
  periodic restoration or replacement (simple
  replacement, overhaul)
• Condition based probability of a failure is
  constant regardless of time.Causes design,
  manufacturer, overhaul, installation errors,
  inappropriate initial operating and maintenance
  procedures ? measurement, inspection ?detect
  ?repairs , corrective actions

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Preventive Maintenance
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Preventive Maintenance

• PM program includes both condition-based and
  time-based ?tasks grouped by periodically and by
  skill
• PM program comprehensiveness
• PM coverage critical equipment
• PM compliance PM routines
• Work generated from PM routines number of
  maintenance actions

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Diagnostic Technologies

• The objective of the inspection ? a warning ? the
  repair could be planned , scheduled, and
  completed to minimize the impact on operations
  and total cost.
• Techniques are used to access the condition of
  equipment
• Vibration Analysiscompare the vibration
  characteristics (parameters) of the current
  operation to a base line ? mechanical equipments.
  Three common types Broad-band monitors
  total machine train Octave-band compare the
  spectrum ranges to the predetermined values ?
  deviations Narrow-banddetermine specific
  problem area,cause

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Diagnostic Technologies

• Oil analysis look at the chemical composition of
  the oil and foreign materials in it.
  Techniques Ferrography and magnetic chip
  detection ? iron- based wear
  Spectrometric oil analysis measures the presence
  and amounts of contaminants in the oil ?every
  elements ?wear particles generated in the early
  stages of failure Chromatography
  ?lubricant properties changes
• Thermography measures surface temperature ?poor
  electrical connections, heating wears, critical
  boiler and turbine component overheating, etc.

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Diagnostic Technologies

• Ultrasonics ?determine faults and anomalies
  (creck, gaps, etc.) in welds, tubes, structures,
  shafts, piping, etc.
• Electrical effects monitoring ? corrosion,
  motors, generators
• Penetrants ?detect cracks and discontinuities on
  surfaces

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Elements of Planned Maintenance

• Planned maintenance refers to maintenance work
  that is performed with advance planning,
  foresight, control and records. It includes the
  whole range of maintenance and it applies to
  replacement, preventive, and break down
  strategies.
• Characteristics
• The maintenance policy has been stated carefully
• The application of the policy is planned in
  advance
• The work is controlled to conform to the original
  plan
• Data are collected, analyzed, and used to provide
  direction for future maintenance policies

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Elements of Planned Maintenance

• Developing procedure
• Plan administration select a task force and its
  head to initiate and develop the plan.
• Facility Inventory a list of facilities, parts
  in a site ?identification
• Identification of equipment code ?location,
  machine type, machine number, etc.
• Facility register is a file containing technical
  details about items included in the maintenance
  plan ?MIS

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Elements of Planned Maintenance

• Maintenance schedule developed a comprehensive
  list of maintenance tasks to be performed on each
  equipment.
• Job specification describe the procedure for
  each task
• Maintenance program allocate maintenance tasks
  to time periods ? coordination workloadgtlt
  requirements
• Program control execute maintenance program
  ?monitor ? control actions