TABLE OF CONTENTS The preventive and corrective maintenance actions described in Chapter 3 get completed in varying times depending on the component involved, its physical characteristics and its location in the equipment, the skill levels of the maintenance personnel, the work disposition state of this personnel, the types of maintenance equipment available, the environmental conditions under which they work, etc. As a result, even for identical components in identical locations, such maintenance action times will vary from one failed component to the next identical failed component in identical equipment. This naturally leads to each specific maintenance action's time being distributed. Such distributions may be the exponential, the normal, the lognormal, the Weibull, the gamma, and others. Most government specifications favor the use of the lognormal distribution as best representing the active repair or restoration times in particular. The application of the lognormal distribution to the determination of the active repair or restoration times is illustrated next.
Given the active times-to-restore data of Table 5.1 for a system in which a specific part fails, do the following:
| 1 | 2 | 3 |
|---|---|---|
| Group number | Times to restore, t j, hr | Frequency of observation, n j |
| 1 | 0.2 | 1 |
| 2 | 0.3 | 1 |
| 3 | 0.5 | 4 |
| 4 | 0.6 | 2 |
| 5 | 0.7 | 3 |
| 6 | 0.8 | 2 |
| 7 | 1.0 | 4 |
| 8 | 1.1 | 1 |
| 9 | 1.3 | 1 |
| 10 | 1.5 |
