Research on rail cars failure process

Abstract

In railway sections where passenger flow is less intense (fewer than 100 passengers per train) rail cars are used instead of diesel multi-units. As they are more fuel efficient, the fault of rolling stock is also expected to decrease. However, rail cars as well as all types of rolling stock break down. The aim of present analysis is to examine rail car failure patterns and to compare them with the failure patterns of other types of rolling stock. 12 rail cars of series “PESA 620M” have been used during the analysis which has been carried out in Vilnius diesel train depot. According to statistical data there has been calculated fault-free operation of rail cars probability as well as examined its dependency on the run-in of a rail car. One of the main indicators of the reliability of rail cars (like of any other machine) is their fault-free operation probability. Analyzing the change of probability of rail cars’ fault-free operation according to run-in, there has been assessed rail cars’ ramming by driving criterion: fault-free operation probability values were found lower when examining rail cars at the beginning of their exploitation than after 2000–3000 engine hours of their exploitation. The change of fault stream when rail cars’ run-in changes can be described relatively precisely by grade function. Such description is not only mathematically correct, but also logical. As it was noted, the reliability of rail cars is lower at the beginning of their exploitation, when the run-in rises this stream is gradually decreasing. However, this decrease is inconsistent. Therefore, to analyze the change of fault stream more precisely, this inconsistency which is determined by technical maintenance of rail cars needs to be assessed. After repairs the reliability of a rail car temporarily increases, that is why the fault stream declines. Rail cars’ fleet renewal strategy has been assessed by periodically introducing batches of rail cars. When introducing a new batch of rail cars after certain number of engine hours the extremes of their fault streams may gather causing a phenomenon similar to resonance (leading to significant total extremes of a fault stream) By filling rail car fleet with two equal batches it is clear that the average of fault stream at the run-in of 5000 engine hours has minimum. This minimum can be filled by adding the third batch of rail cars (consequently, the third maximum will appear in the schedule which should compensate the minimum of the fault stream at 5000 engine hours). Having completed the analysis it is evident that when forming the rail car fleet and acquiring them in even batches it is possible to choose their introduction period so that the fault stream minimum in some batches would match the maximum in others. In this way the total fault stream of the fleet would change consistently. Also, if the last batch of rail cars is the same as the ones already introduced, it can destabilize the total fault stream of the fleet before it stabilizes. If when upgrading rail car fleet, the fault stream maximum of the added batch matches the maximum of the previous batch and it distorts the change consistency of the total fault stream of the fleet, this batch should be minimized.