Statistical Methods in Reliability Diesel Generator Fan Failure Data Jesse Lesperance Spring 2008

Diesel Generator Fan Failure Data Manufacturer: DGF, Inc. - a leading manufacturer in industrial generator equipment developed, produced and distributed a new type of radiator fan for industrial diesel generators. New product line provided a 5000 hour warranty on each new fan. To date 70 fans have been sold and there usage-rates differed.  A year after the products release they started receiving fans back for failure at low hour times. (12 of 70 generator fans reported failure) Source: Meeker, William Q. and Luis A. Escobar (1998), Statistical Methods for Reliability Data, John Wiley & Sons, Inc., 8-9, 630

Diesel Generator Fan Failure Data Life distribution of units censored at a given age must be the same as the life distribution of the units that run beyond that age Multiply right-censored with failure times exceeding some of the running times Type IV censoring Assume that the potential lifetimes are independent and identically distributed with a continuous life distribution Weibully distributed Begin by validating the assumptions and then use this to calculate the MTTF and MRL Non-parametric analysis will need to be performed Use this to answer DGF, Inc’s questions Assumptions: Methodology:

Diesel Generator Fan Failure Data Weibully Distributed Shape: Scale:

Diesel Generator Fan Failure Data  MTTF: 7565 hours  95% CI: 6898 hours to 8231 hours System Information: DGF  System reliability will get better as more units reach there independent life  Poor initial system reliability may be attributed to unnatural usage, but cannot be assessed without additional usage information.  Can anticipate ~2-3 additional failures within the 5,000 hour warranty period. Conclusions: 5000 Hours