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foot of the rails. After the rail section is cut out, its first stress free temperature is determined. The new rail section is cut and replaced and then welded at one end. A "stressing kit" (hydraulic rail tensor), such as the
Permaquip HSM70 Stressor, or other method is used to adjust the other end and make the join ready for welding. If a section of rail must be replaced urgently, a stress check is performed later on.
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The CRT may be reached due to disturbance of the ballast, track components or track geometry. For example, the CRT may be reached due to a removal of a rail section or an
Insulated Block Joint (IBJ). A stressing engineer measures the rail section to be removed and places indicators with marks on the
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Before laying new track, repairing track, or changing the sleepers, the rail is mechanically or thermally altered (stressed) so that its length equals the same at a chosen stress-free temperature; the rail can then be fixed in place with no thermal forces in effect. The stress-free temperature that
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In the design and installation of CWR, a figure known as the "rail neutral temperature" (RNT) is calculated. The tensile and compressive longitudinal forces on the CWR are added. The RNT is the notional temperature when the total equals zero. A similar figure is the "stress free temperature" (SFT).
53:. Environmental cold can lead to the contraction of the fixed railway track causing brittleness and cracks. Before it is installed, the rail is altered by stretching with hydraulic tensors or heated to its stress-free temperature to make these dangerous problems less likely.
110:, standard stress free temperatures vary from 35 to 43 °C (95 to 109 °F). Despite stressing the CWR before installation, a rail may still reach its "Critical Rail Temperature" (CRT). This is the temperature of the rail above which buckling may occur.
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A more recent engineering solution is "VERSE" testing equipment produced by the company, Vortok in 1998. It allows rail engineers to measure stress-free temperature without removing a section of rail. Vortok is
Pandrol Vortok now.
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where a length of a railway buckles laterally (sideways). Other factors that affect CWR condition include the state of the
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U.S. General
Services Administration, National Archives and Records Service, Office of the Federal Register, 2010 p122.
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Railway steel contracts at low temperatures and expands at high temperatures. In extreme cold, a length of CWR suffers
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is a rail engineering process. It is used to prevent heat and cold tension after installation of
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It is the rail temperature at which the rail is the same length as in its unrestrained state.
65:. This stress can cause railway steel to fracture. In extreme heat, a length of CWR suffers
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is used is dependent on environmental extremes and thus varies with location. In the
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Spark, the
Railway Knowledge Hub website 6 January 2017. Accessed 24 February 2018.
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Railroad suppliers provide ways to prevent the track from bending and twisting
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Thermal Rail De-stressing using Low
Voltage Carbon Polymer Technology (C PT)
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Li, Dingquing; Hyslip, James; Sussmann, Ted; Chrismer, Steven (2002).
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Structural Health
Monitoring 2003: From Diagnostics & Prognostics
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Torrent
Trackside website advertisement. Accessed 24 February 2018.
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The Code of
Federal Regulations of the United States of America
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Progressive railroading March 2013. Accessed 24 February 2018.
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351:Vortok company website. Accessed 24 February 2018.
77:and its shoulders; the type and placement of the
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27:"Stressing" redirects here. For other uses, see
150:Train Wreck: The Forensics of Rail Disasters
216:U.S. Government Printing Office, 2000 p91.
175:The Railway Times vol 23 p76 11 March 1871
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315:Permaquip Stressing Kit and Power Packs
253:DEStech Publications, Inc, 2003 p1314.
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172:The Effects of Cold on Iron and Steel
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