Failure rate analysis of four agricultural tractor models in southern Iran
Keywords:failure rate, tractor, storage condition, Khouzestan
Tractors play an important role in agricultural mechanization. A repairable mechanical system (as agricultural tractor) is prone to deterioration or repeated failures. In this study, the owners of three hundred tractors, which include Massey Ferguson (MF285 model and MF399 model), John Deere (JD3140 model) and Universal (U650 model), were interviewed, from five regions of Khouzestan Province. A regression model was used to predict the tractors failure rate. The machine failure pattern was carefully studied and key factors affecting the failure rate were identified in these regions. The data obtained from farm records valid by using questionnaire was separated into two groups according to how those tractors were stored. Results showed that the majority of recorded failures were observed in the electrical system for all tractors. According to the results of the research, different storage policies significantly affected the failure rate for MF285, MF399 and JD3140 tractors (63%, 55.5% and 61.6% respectively), whereas inside storage of U650 tractors slightly decreased the failure rate (7.4%). Also, closed storage condition was found to reduce annual repair and maintenance costs by 33.6%, 33.6%, 29.6% and 2.56% in comparison with open air storage condition for the study tractors respectively. The observational estimate showed that all tractors were in the wear out period under outside storage conditions, against inside storage had a considerable effect on the failure rate of MF285, MF399 tractors and they were commonly in a randomized breakdown period within their useful life, JD3140 tractors were in the beginning of wear out period, but U650 tractors were in the wear out period for both storage conditions. Therefore, it can be said that by storing the tractors out of the weather conditions slowly exposed by failure and breakdowns, especially in warm climate and presented of dust haze phenomenon.
Keywords: failure rate, tractor, storage condition, Khouzestan