Reliability Centered Maintenance

Day II Salih O. Duffuaa

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.

Impact Of RCM On O&M Costs

1984 RCM pilot study At FP & L’s 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.

RCM Impact

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

Steps of RCM

System selection and data collection

System boundary definition

System description and Functional Block Diagram

RCM Steps Continued

Systems function and functional failures

Failure mode and effect analysis

Logic tree analysis (LTA)

Task selection

Level of RCM Application

Part

Component---Assembly

System

Plant

System Selection and Data Collection

Basis of system selection

What data and information to collect

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.

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.

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

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

Example of system Boundary Definition

Refer To Transparencies --- Figure 5.4

System boundary details --- Figure 5.5 and Figure 5.6

System Description and Functional Block Diagram

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

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

System Description Cont.

Elements of System Description

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

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

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

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

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.

Correct and Not Correct Function Statements

Provide alarm to control room if block valves are < 90 percent open (w)

Provide alarm to control room if flow rate is < 90 percent of rated flow

Provide water-cooled heat exchanger for pump lube oil (w)

Maintain lube oil 130 o F.

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

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)

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

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.

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

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

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

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

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

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.

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.

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.

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. 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