Technology Digests / Influence of De-anchor Length on RNT after Cold Temperature Rail Breaks

TD24-017

June 25, 2025
Authors
  • Stephen Wilk
  • Christopher Johnson
  • Duane Otter
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Key Findings

  • Different de-anchor lengths (10, 190, and 520 feet) did not produce significant long-term differences in the RNT profile during re-establishment of simulated cold-weather rail breaks in CWR track.
  • If a localized high RNT-spot was produced during RNT re-establishment, the testing showed train operations smoothed the RNT profile out to a more uniform condition. The majority of RNT redistribution occurred within the first 5 MGT.
  • The rail may slip through the rail anchors during a rail break. If a short de-anchor length is used, the subsequent pulling (RNT establishment) may result in loose anchors on the side of the rail break if the anchors do not slip through the rail during the pull. The length of loose anchors is likely dependent on track and track component condition.

Influence of De-anchor Length on RNT after Cold Temperature Rail Breaks

MxV Rail investigated whether various de-anchoring lengths affected the rail neutral temperature (RNT) profile after welding and subsequent traffic. Conducted at the Facility for Accelerated Service Testing (FAST®) between January and March 2024, the testing simulated a cold weather rail break (rail in significant tension) in track with continuously welded rail (CWR). Current guidance for CWR track is to de-anchor through the affected influence zone before re-welding. The influence zone is defined as the region where the longitudinal rail forces (i.e., RNT) are affected by the rail break. This distance may extend up to 600 feet, depending on rail temperature at the time of the break, the RNT, and the longitudinal resistance. As part of an ongoing effort to provide improved guidance during RNT re-establishment, this work was supported by the Association of American Railroads (AAR) under its Strategic Research Initiatives (SRI) program. RNT RE-ESTABLISHMENT When a cold weather rail…