Patent ID: 6278920
Filing Date: 2001-08-21
Classification: G05B,G06Q

Abstract:
A method for establishing a confidence level in a replacement schedule for a component used within a group of machines, said method comprising the steps of:a. selecting an anticipated life expectancy T for the component;b. establishing an indicated reliability R.sub.1 for the component;c. establishing a time increment t over which one or more units of the component produced a failure;d. establishing a number of failed units F of the component that had to be replaced over the time increment t;e. determining a number P of units the population of the component in active use within a particular group of such machines;f. computing a minimum-mean-time-between-removals .theta..sub.1 based upon the anticipated life expectancy T and the indicated reliability R.sub.1 ;g. computing an upper limit on unreliability P.sub.u based upon time increment t and the minimum-mean-time-between-removals .theta..sub.1 ;h. searching a plurality of Gamma Confidence Level look-up tables based upon three factors, namely, the number of failed units F, the population of the component within a particular group of machines, and the upper limit on unreliability P.sub.u to determine whether such three factors simultaneously appear within one or more of the plurality of Gamma Confidence look-up tables;i. if the three factors do not simultaneously appear on any of the plurality of Gamma Confidence lookup tables, then raising the indicated reliability R.sub.1 in step b., and repeating steps f., g., and h. until the three factors simultaneously appear on one of the plurality of look-up tables;j. determining, based upon steps h. and i., the Gamma Confidence Level for the population of the component within the group of machines;k. if the Gamma Confidence Level determined in step j. is 75% or less, then reducing the anticipated life expectancy T, and repeating steps f., g., and h. until the Gamma Confidence Level is 75% or higher; andl. replacing the component within the particular group of machines when the usage of the component reaches the minimum-mean-time-between-removals .theta..sub.1 computed in step f.