Growth Curve Overview

Use growth curves to analyze life data from a repairable system. A repairable system is one in which the parts are repaired instead of being replaced when they fail. For example, automotive engines are usually repaired many times before being replaced. System repair data usually consist of successive failure (or repair) times. However, data can also be measures such as distance from a reference point or the length of a crack.

·    Use nonparametric growth curves to estimate growth curves of the mean cost of maintaining the system or the mean number of repairs over time without making assumptions about the distribution of the cost  or number of repairs.

·    Use parametric growth curves to estimate growth curves of the mean number of repairs and the rate of occurrence of failure (ROCOF) over time using a power-law process or a homogeneous Poisson process.

Use nonparametric and parametric growth curves to determine whether a trend exists in times between successive failures of a repairable system; that is, to determine whether system failures are becoming more frequent, less frequent, or remaining constant. Use this information to make decisions concerning the future operation of your system, such as:

·    Setting maintenance schedules

·    Making provisions for spare parts

·    Assuring suitable performance

·    Forecasting repair costs