Squat Treatment by Way of Minimum Action Based on Early Detection to Reduce Life Cycle Costs

Squats are a type of rolling contact fatigue on the top of rails of straight tracks or shallow curves. In some countries they have become a major type of rail damage. Although it is widely recognized that preventive and early corrective actions are cheaper than late remedies such as rail replacement, timely treatment is hindered by the lack of automatic detection of early squats. So far, the treatment of squats has mainly been dependent on ultrasonic detection, which detects deep cracks and is applicable only to severe squats. The life cycle costs (LCC) of squat-infected track are therefore high. The operational safety and availability of the networks are also adversely affected. Based on a new method which detects initiating squats, this paper proposes a methodology for squat related LCC reduction. First a squat classification is introduced that facilitates early identification of squats. Then the growth phases of squats are discussed; typical growth rate of squats is analyzed, and thereupon based threshold values for minimum action by rail grinding are proposed. After a review of the currently available detection methods, the new detection method is presented, with results of field test demonstrating the capability of the method to detect light squats. Finally, a case study of the LCC of a monitored squat-infected track section shows that the proposed treatment can significantly reduce the LCC. In addition, operational safety and network availability can also be improved.