For NS, TORFC = Low RCF

William C. Vantuono photo

During a recent two-year period, engineers from Norfolk Southern (NS) and Transportation Technology Center, Inc. (TTCI) evaluated rail performance on four curves on the NS Whitethorne District, near Roanoke, Va., during two periods of 39 to 40 MGT (million gross ton) traffic accumulation. The objective was to document RCF (rolling contact fatigue) development, rail friction, and rail wear as influenced by the TORFC (top-of-rail friction control) materials NS currently uses. The rails were ground at the beginning of the test and again halfway through the test in April 2017, with the intent of producing similar conditions, after which a 39-40 MGT monitoring effort commenced, each with a different TORFC product.(1,2) The curve rails differed by rail mill, age and wear.

Based on rail wear data and coefficients of friction values, both TORFC materials were most effective on the curve with TOR applicators placed nearby, and less effective on a downstream curve. Observations suggested TORFC is less effective in inhibiting RCF formation and growth on rail with pre-existing surface cracks than on rail without any pre-existing surface cracks. Rail performance for the two TORFC materials was evaluated for wear using MiniProf rail profiles, for surface conditions using dye and penetrant, and for rail friction measurements by tribometer during monitoring of TORFC material usage. One curve (control) was not protected by any TORFC application system, and the other three curves had varying amounts of TORFC material applied.

Results from other long-term evaluations on new rails where the application of TORFC materials started immediately after installation indicated TORFC allowed little or no RCF to develop, compared to identical rails installed nearby that were not subjected to TORFC, and which did develop significantly more RCF.3,4 

Throughout testing, TORFC material application amounts varied between sites; thus, effectiveness may not have been uniform throughout the evaluation. After 39-40 MGT in the first phase, RCF tended to become more severe and dense at the middle and end of the curves, suggesting the first TORFC material became less effective farther into the curve and away from the TORFC applicators. The second TORFC material did not fully prevent RCF from forming or growing.

After grinding for the start of this second phase, rails exhibited more cracks than at the start of the first phase. Both TORFC materials did not appear to accelerate spalling at existing cracks. Of the three curves exposed to TORFC, two exhibited more deterioration due to RCF on the high rail than on the low rail. Although TORFC materials were applied to both rails at each applicator site, both materials appeared to help the low rail more than the high rail—which might be related to the specific train operating conditions on this track. No adverse top-of-rail coefficients of rail friction were measured; all readings were at or higher than AREMA-recommended minimum values.

The top photo in Figure 1 shows the rail surface condition at the middle of one test curve after grinding and conclusion of the first phase of testing. The rail had existing gage corner RCF, and grinding did not remove the RCF completely. The same location is shown after the end of the second phase with the second TORFC material in Figure 1’s bottom photo. Minor pitting started in the center of the top of rail, but gage corner RCF has not changed much since the start of the second phase. This shows that the second TORFC material did not accelerate RCF growth or development.

References

1. Banerjee, A., K. Conn, B. Kerchof, and R. Reiff, December 2017, “Effects of Top-of-Rail Friction Control Materials on Rail in Revenue Service,” Technology Digest, TD17-035. Association of American Railroads, Pueblo, Colo.
2. Banerjee, A., K. Conn, B. Kerchof, and R. Reiff, November 2018, “Top-of-Rail Friction Control Material Influence on Rolling Contact Fatigue and Rail Wear in Revenue Service,” Technology Digest, TD18-031. Association of American Railroads, Pueblo, Colo.
3. Reiff, R., and K. Conn, August 2011, “Implementing Top-of-Rail Friction Control on Norfolk Southern Preliminary Results of Rail Wear Rates,” Technology Digest, TD11-027. Association of American Railroads, Pueblo, Colo.
4. Reiff, R., June 2007, “Wayside-Based Top-of-Rail Friction Control: 95 MGT Update,” Technology Digest, TD07-019, Association of American Railroads, Pueblo, Colo.