Chapter 12Maintainability and Availability

12.1 introduction

Availability analysis of the system requires a knowledge:

(1) How the components are functional connected.

(2) The failure process of the component.(3) The method of operation and the

definition of the failure.(4) The repair or maintenance police.

12.2 Maintainability

12.2.1 ConceptMaintainability M(t) : the probability of

repairing a failed component or system in a specified period of time.

Two kinds:Preventive maintainabilityCorrective maintainability

12.2.2 Preventive maintainabilityreliability of the system

System Reliability

Example 12.2 derive the condition under preventive maintenance is beneficial to the

12.2.3 imperfect maintenance

12.2.4 Repair time distribution

12.2.5 Unrepaired failure

Number of unrepaired failure in time

tetM 1)(

oT

12.2.6 Optimum replacement strategy

The total number of the times the component is replaced is given by

rm nnn

12.2.7 Spare parts requirement

The probability of having n failure in time t :

Example 12.9 Three kind of component in an system : 20 in type A (failure rate 0.002), 130 in type B (failure rate 0.0001), and 100 in type C (failure rate 0.0005). Find the number of spare parts required to cover the mission period 30 days and 99 percent of probability

12.3 Availability

12.3.1 definition

3. Steady state availability

4. Inherent availability

5. Achieved availability

6. Operational availability

12.3.2 Availability Analysis

12.3.3 Development of model

12.3.4 system with single component

12.3.5 Series system

One repair person :

Two repairperson

12.3.6 Parallel system

One repair person

Two repair persons

22

2

10 22)(

PPA

12.4 Optimization Approach