Brad Kerchof
Norfolk Southern Railway
Abstract:
Validation of Rail Crack Measurement Devices on NS
Small cracks that develop in the wheel contact band of the rail are the first visible sign of rolling contact fatigue (RCF). These cracks, if not removed, can grow horizontally and cause pieces of rail metal to break out, or they can grow vertically and develop into transverse defects. In addition, these cracks, no matter what their orientation, weaken the rail metal and allow an accelerated change in rail profile. Knowing if cracks are present and knowing their depth are important to executing an effective grinding program and maximizing rail life.
A number of rail industry suppliers have focused on developing technologies that measure crack depth. Those suppliers have enjoyed the support of several railroads and research organizations, which have provided revenue service testing opportunities and lab validation work.
This presentation focuses on work that Norfolk Southern has done in 2014 and 2015 with two new technologies supplied by Sperry Rail Service and group including Rohmann, Advanced Rail Management and International Engineering. SRS tested a single rail, walk-behind eddy-current device on the rail of two curves that were subsequently removed for lab analysis. The ARM group provided a two-rail, tow-behind eddy-current buggy, and measurements taken post-grind were compared to non-destructive testing results and to measurements taken pre-grind.
The assessment of the recently tested devices remains consistent with the conclusions reached following previous validation work: Crack measurement devices seem to do a reliable job measuring crack length, but not crack depth.
This work builds on work shared at the last two WRI Seminars, when NS presented the results of crack measurement validation work involving measurement devices provided by MRX and Rohmann.