RELIABILITY-ANALYSIS OF HYDRAULIC SYSTEMS OF LHD MACHINES USING THE POWER LAW PROCESS MODEL

Earlier, a preliminary study of the reliability characteristics of a fleet of load-haul-dump (LHD) machines deployed at Kiruna mine showed that the engine and the hydraulics are the two most critical subsystems. Hydraulic systems are selected for further study because such systems are still under a development phase. Maintenance data for two years for these machines are analyzed. The tests for trends and serial correlation showed that times between successive failures for the hydraulic systems are in most cases not independent and identically distributed. Goodness-of-fit tests showed that the power law process model provides a good fit to the failure data of the hydraulic systems. Methods for parameter estimation in the power law process model and estimation of optimal maintenance intervals for such systems are presented. Emphasis is on the use of graphical methods for data analysis.