This research study proposed a novel algorithm, called time-counter, to optimise inspection intervals of production systems. The developed algorithm was applied to two active draglines. The algorithm evaluated random uptime/downtime characteristics of the draglines and the planned dragline halts in the mine. Physical and random non-physical costs were included and annual maintenance cost minimisation was achieved. Dragline-1 and Dragline-2 inspection intervals were optimised as 232 and 184 h and their maintenance costs were reduced by 5.9 and 6.2% compared to the current interval, respectively. This study is the first initiative in cost-effective inspection interval optimisation of a mining machinery.