Non-uniformity in braking in coaching and freight stock in Indian Railways and associated causes

• Finite element model that can predict wheel temperatures is presented and validated.
• Normalized wheel temperature rise is shown to determine non-uniformity in braking.
• Non-uniformity in braking is monitored in passenger, express, and freight trains.
• Ratio of maximum to average braking effort is as high as 7 for freight trains.
• Faulty distributor valves result in abnormally high braking in some coaches.

Non-uniform braking of wheel sets in locomotives and coaches/wagons can have disastrous consequences e.g. from wheel locking leading to derailments or thermal cracking, particularly under emergency braking conditions. Currently, while rigorous testing is used to characterize brake block characteristics and brake application time, no methods exist to determine the “variability” in braking across the different wheel sets, e.g. from differences in brake block characteristics, brake rigging, and performance of distributor valves. In this work, temperature rise in railway wheels is used to gauge normalized heat input coming in to wheels from braking. Two sets of field trial data are used to investigate variability of braking: (i) continuous rim temperature data for locomotive wheels and (ii) one time measurement of wheel rim temperatures of all wheels. The data is used to pin point the causes for non-uniformity in braking and to characterize the extent of non-uniformity. Non-uniformity in braking is found to be particularly severe in freight trains as compared to passenger trains. Faulty distributor valves are seen to result in maximum braking effort on wheels that is as high as seven times that of average braking effort in freight trains.