Regression Analysis and Modeling of Failure Rate and its Effective Factors on Tractors in Some Cities of Khuzestan Province

Effective operation of a system is related to acceptable programming of repair and service activities. Efficient managerial programming is associated with accurate estimation of maintenance system parameters. In this study، four tractors failure rate was investigated by completing 300 questionnaires from tractor operators in Khuzestan Province. The operators were interviewed in four regions of the province. Under study variables included driver experience، level of education، driving license، skill training course، work location (region and city)، type of service and maintenance، storage conditions، distance to first workshop، distance from shelter to farm، machine age، annual use hours and number of failure. Regression analysis by estimating an exponential function showed that the variables such as age of tractor، annual hours used and type of service and maintenance affected the failure rate of each four type tractors. For one percent increase in age of tractor and annual use hours، failure rate increased about 0. 6% and 0. 24%، respectively. Also، failure rate in MF285، MF399 and U650 tractors was about 0. 383، 0. 453 and 0. 143 percent more than JD3140 tractor، respectively. The preventive maintenance causes 0. 252 percent decrease in failure rate.