Reliability Centered Maintenance: Module III

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• Reliability Centered Maintenance Module III
• Salih O. Duffuaa

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Reliability Centered Maintenance

• Objective of Module
• Present the steps of RCM
• Demonstrate the steps clearly
• At the end each participant should
• Understand the basics of RCM
• Initiate an RCM project
• Participate effectively in teams implementing
  RCM.

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Impact Of RCM On OM Costs

• 1984 RCM pilot study At FP Ls Turkey Point
  Nuclear plant provided evidence that RCM could
  impact O M costs
• Survey conducted by Electric Power Research
  Institute provided more evidence that RCM has
  impact on Cost.

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RCM Impact

• Plant trip reduction
• Documented Basis For PM
• Efficient PM Planning
• Decrease in corrective maintenance
• More accurate spare parts identification
• Increase plant availability

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Steps of RCM

• System selection and data collection
• System boundary definition
• System description and Functional Block Diagram

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RCM Steps Continued

• Systems function and functional failures
• Failure mode and effect analysis
• Logic tree analysis (LTA)
• Task selection

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Level of RCM Application

• Part
• Component---Assembly
• System
• Plant

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System Selection and Data Collection

• Basis of system selection
• What data and information to collect

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Criteria for System Selection

• 1- Systems with high PM tasks
• 2- Systems with high breakdown maintenance
• 3- Systems with large contributions to full or
  partial outages.

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Criteria for Selection

• 4- Systems with high cost of CM actions
• 5- Systems with high content of concern with
  respect to safety and environmental issues
• 6- Combinations of the Above
• In a Typical selection process at Florida Power
  Light Fossil Power Generation 5 is used coupled
  with Parato chart.

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Information Collection

• System piping and information diagram
• System schematic block diagram
• Vendor manual
• Equipment history file
• System operation manual
• System design specification and data description

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Importance of system Boundary Definition

• It provides knowledge of what hs or has not been
  included
• The boundary determines what comes into and what
  leave the system ( in and out)
• Boundary definitions must be clearly stated and
  documented

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Example of system Boundary Definition

• Refer To Transparencies --- Figure 5.4
• System boundary details --- Figure 5.5 and Figure
  5.6

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System Description and Functional Block Diagram

• System description
• Functional block diagram
• In/out interfaces
• System work breakdown structure
• Equipment history

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System Description

• Tangible benefit of system description
• Account and document baseline definition of
  system as existed
• Ensure comprehensive understanding of the system
• Aid in identifying critical parameters that
  contribute to degradation and loss of function

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System Description Cont.

• Elements of System Description
• Functional description/ key parameters
• Redundancy features
• Protection features
• Key instrumentation features
• See figure 5.7 in transparences

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Functional Block Diagram (FBD)

• The FBD is a top-level representation of the
  major functions the system performs
• It consists of functions no equipment appear.
  labeled functional subsystems
• In/out interfaces shown
• See figure 5.8

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System Work Breakdown Structure (SWBS)

• Carryover from Ministry of Defense Terminology
• Compilation of the equipment lists in each
  functional subsystems shown in the fbd
• Include all components within system boundary
• list all instrumentation components
• See figure 5.10 and 5.11 for equipment history
  file

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Systems Functions and Functional Failures

• List all functions
• In essence every out interface should be captured
  into a function statement
• Two additional sources for functions
• Internal out interfaces between functional
  subsystems
• Passive functions
• List all functional failures

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Correct and Not Correct Function Statements

• Provide 1500 psi safety relief valves(w)
• Provide for pressure relief above 1500 psi
• Provide a 1500 gpm centrifugal pump on the
  discharge side of header 26 (w)
• Maintain a flow of 1500 gpm at the outlet of
  header 26.

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Correct and Not Correct Function Statements

• Provide alarm to control room if block valves
  are lt 90 percent open (w)
• Provide alarm to control room if flow rate is lt
  90 percent of rated flow
• Provide water-cooled heat exchanger for pump lube
  oil (w)
• Maintain lube oil ? 130 o F.

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Functional Failure

• The focus on loss of functions not loss of
  equipment
• Absolutely necessary to distinguish between
  function loss conditions
• Most functions have more than one loss condition
• Distinction in loss condition usually leads to
  different failure modes

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Functional Failures

• Function provide for pressure relief above 1500
  psi
• Functional failure
• (a) Pressure relief occurs above 1650 psi
• (b) Pressure relief occurs prematurely ( below
  1500psi)

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Examples of Different Functional Failure

• Function Maintain a flow of 1500 gpm at the
  outlet of header 26
• Functional failures
• (a) Flow exceeds 1500 gpm
• (b) Flow is less than 1500 but greater than 1000
  gpm
• ( c ) Flow is less than 1000 gpm
• Function ad functional failure are recorded on
  figure 5.12

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Failure Mode And Effect Analysis(FMEA)

• Functional failure and equipment matrix
• This matrix address which system equipment could
  play a role in the creation of functional
  failures. this is done by completing the matrix
  in figure 5.13.

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Failure Mode and effect Analysis (FEMA)

• Record The following on figure 5.14
• Component
• Failure Mode --- Figure 5.15 provides typical
  description for failure modes
• Failure cause
• Failure effect
• Local
• System
• Plant

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Redundancy General Rule

• If redundancy prevent loss of function then a
  failure shielded by redundancy should be given
  different priority than a failure mode that can
  singly defeat a necessary function.
• If multiple independent failure in a redundant
  situation is possible the we identified a design
  issue

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Logic Tree analysis (LTA)

• The purpose of this step is further prioritize
  failure modes that survive step 5. the
  prioritization is done qualitatively using the
  logic tree diagram in figure 5.16 and form 5.17

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Task selection

• In this step the appropriate maintenance task is
  selected to prevent the loss of function.
• The task selection road map in figure 5.18 is
  used for this purpose with form 5.19

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Sanity Checklist

• The purpose of this check is to review
  critically all components failures that are
  treated run to failure to see if this decision is
  optimal.
• Explain form 5.21

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Terms On Sanity Checklist

• marginal effectiveness it is not clear that the
  rtf costs are significantly less than the current
  pm costs
• High-cost failure while there is no loss of
  critical function, the failure mode is likely to
  cause extensive damage to the component that
  should be avoided.

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Terms In Sanity Checklist

• Secondary damage similar to 2, except that there
  is a high probability extensive damage in
  neighboring components.
• OEM conflict The original manufacturer
  recommends a PM task that is not supported by
  RCM. It is very sensitive of warranty conditions
  are involved.

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Terms In sanity Checklist

• Internal conflict Maintenance or operation feel
  strongly about the PM task that is not supported
  by RCM.
• Regulatory conflict regulatory body established
  the PM, such as EPA.
• Insurance conflict similar to the above two.

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Comparison Between RCM Findings and existing
Situation

• RCM-based and current tasks are identical.
• Current PM tasks exist, but need to be modified
  to meet RCM-findings.

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Comparison Between RCM Findings and existing
Situation

• RCM-based PM tasks are recommended where no
  current tasks exist.
• Current PM tasks exist where no RCM tasks-based
  task recommended-candidates for deletion