Technology Digests / Rail Neutral Temperature Changes from Train Operations after Welding

TD26-023

Date Posted: October 7, 2026
Authors
  • Stephen Wilk
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Key Findings

  • Train operations redistributed rail longitudinal stresses at both the high- and low-RNT pockets placed during welding for all four rail cut tests. This redistribution resulted in the RNT either increasing from a low-RNT pocket or decreasing from a high-RNT pocket and stabilizing closer to the surrounding pre-break RNT. The redistribution stabilized within the first 5 million gross tons (MGT).
  • The cut, weld, and redistribution all matched RNT re-distribution theory.
  • Train operations redistributed the RNT gradient to between 1.5 and 4.7°F/100 ft., and this slope appears to be dependent on the initial post-weld gradient. The final RNT gradient allows estimations of RNT changes and post-tonnage RNT distributions.

Rail Neutral Temperature Changes from Train Operations after Welding

MxV Rail performed multiple rail cut tests in 2025 and 2026 to observe how train operations “redistribute” localized high- and low-rail neutral temperature (RNT) pockets after welding. Standard railroad practice after rail or weld breaks is to re-establish the RNT to target neutral temperature (TNT). However, if a break occurs in cold weather, re-establishing the RNT at that time may not be practical, and railroads may opt to install a temporary repair at a lower RNT and then readjust the RNT later by installing a final repair at target RNT before summer. Railroads have observed that the RNT at the temporary repair can increase after train operations and season changes. Estimating the changed RNT can be important when prioritizing readjustments. Alternatively, electric flash butt (EFB) welding in summer months can sometimes produce above-target RNTs because the EFB consumes rail during the welding process. MxV Rail engineers used the Phase II…