Abstract: Based on the research of gantry crane reliability and performance degrading regularity, a new reliability model, which is called isodegrading model, is put forword and applied effectively in determining the recommending overhaul and available life parameters of railway gantry cranes. The core of the isodegrading model is that there are isodegrading rate of machine overhaul reliability and operational parameters between neighbouring overhaul circles and isodegrading speeds between the reliability and operational parameters.

Key words: Isodegrading model, Machine, Overhaul circle, Reliability