008 maintainability theory

Maintainability Maintainability Theory IITheory II

Jang Jusu

MOASOFT Training Course for Reliability

Maintenance Vs. Maintainability-Maintenance is the act of repairing or servicing equipments

-Maintainability is a design parameter intended to minimize repair time.

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Downtime

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Maintainability CriterionMaintainability Criterion

Criterion-1 Availability is a critical parameter?Criterion-2 Availability is not a critical parameter!Criterion-3 Maintenance time is unknown!!!

Criterion-4

Right hand skewness is expected :-simple equipment-simple maintenance concepts-comprehensive diagnostic routines

Criterion-5 Lognormal or skewed right hand

Criterion-6 Environmental or operational circumstances limit maintenance time

Criterion-7 Human resources allocation and planning have overriding priority

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Criterion

Measure

Mct or Mpt Mct M(max)

MMH/OH

Mct and Mct(Max)Mpt and Mpt(Max)

Mct and M(max)

C-1C-1 XXXXXX

XX XX

C-2 XX

X X X

C-3C-3 XX XX XX

C-4 X X

C-5C-5 XX XX XX XX

C-6 X X X X

C-7C-7 XX

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Maintainability CriterionMaintainability Criterion


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System Effectiveness : AvailabilitySystem Effectiveness : Availability


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System Effectiveness : DependabilitySystem Effectiveness : DependabilityDependability can be described as the probability that a

system will accomplish its assigned mission.

D = OM(1 – OR) + OR

-OM : Operational Maintainability-OR : Operational Reliability


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Maintenance Model – Maintenance Model – Optimum Number of InspectionsOptimum Number of Inspections

xTkTxT CMT

PMTDT

2/1

PMT

CMToptimal T

Tkx


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Maintenance Model – Maintenance Model – Optimum replacement time interval(year)Optimum replacement time interval(year)

)(21

PYPYFYFYT MCOCxxICMCOCC

2/12

PYPY

optimal MCOCICx


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Maintenance Model – Maintenance Model – Optimum replacement time interval(hour)Optimum replacement time interval(hour)

x

dxxCCC

x

MRPM

T

0

)(

2/12

PYPY

optimal MCOCICx


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008 maintainability theory

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