DETERMINATION OF TIMELINESS COST USING METHOD OF AVERAGE WORKABILITY ROBABILITY BASED ON RELIABILITY FUNCTION OF FARM TRACTORS

There is an optimum time for implementing field operation of a crop in each region. If the operation were accomplished sooner or later, it might cause a reduction in yield quantity and quality that is named timeliness cost. The purpose of this study is to survey the timeliness cost of harvesting operation of sugar cane based on reliability function of MF285 tractors operating in Debal Khazaei Agro-Industry Co. in Khuzestan, a province of Iran. MF285 tractors have low reliability in Iran, and due to their low reliability have an uncertainty in implementation of farm operation, though it is not considered in ASAE equation for calculating of timelines cost. This uncertainty causes cost which is a part of timeliness cost and is produced due to tractor failure during farm operation. Thus, the reliability function of tractors based on distribution fitting of tractor operation times to a failure is obtained. Then, other timeliness factors in the formula are determined according to the study conditions. At last, tractor timeliness cost of harvesting operation caused by MF285 tractors is calculated using new modified equation and after that, its relation with farm tractor mission time (tm) is determined. Results showed that timeliness cost increased whatever machine mission time increased way that intensity of increase in lower mission times was less than upper ones.