EQUIPMENT is being trialled at Heathfield on ARTC’s Adelaide - Melbourne main line to detect and measure wheel squeal.
Trains negotiating this sharply-curved and steeply-graded section generate high levels of squeal and flanging noise in a densely-populated area, and investigations suggest that a large percentage of wheels with high noise emission readings have an irregular angle of attack or suffer from inter-axle misalignment.
Developed by Vipac from its RailBAM acoustic bearing monitoring technology installed primarily on heavy haul lines at 26 locations worldwide, the Railway Squeal Acoustic Detection system consists of a microphone array and trackside sensors to measure wheel speed and direction and to read wagon identification AEI tags; the microphone array is located 6m from the inner rail of a curve. Data streams are connected to a PC-based data acquisition system that tracks individual wheelsets, recording and analysing the noise caused by the wheel-rail interaction.
Emissions are classified as squealing or flanging and then ranked against specified criteria. Data is imported into a trending database that produces statistics for analysis against operating parameters, the condition of rolling stock and environmental conditions. This data can be accessed through an ARTC portal so that operators can remove ’repeat offenders’ or other vehicles for maintenance that may include adjustment to side bearers, brake rigging or bogie springs.
Early results indicate that squeal occurs more on downhill runs, with almost all freight wagons going uphill ’passing’. The difference is associated with the train being stretched as it travels uphill with wagons bunching as dynamic braking is used on the downgrade. Most high noise emissions occur during cooler periods of the day between dusk and dawn, implying that relative humidity on the rail head is an important parameter. There appears to be no significant relationship between squeal and speed.