scope:

This standard applies to all LU staff responsible for the installation or maintenance of of track assets. It covers all ballasted flat bottom and bull head track Continuous Welded Rail (CWR), long welded rail and short rail) and conductor rail.

Subject to the length limits given in standard S1157, short lengths of CWR do not require stressing. Requirements in this standard regarding stressing, Stress Free Temperature (SFT) and Critical Rail Temperature (CRT) do not apply to this "unstressed welded rail".

This standard does not cover rail stressing methods in detail. Instead, reference is made to Network Rail standard NR/L2/TRK/3011 where this is applicable to London Underground (LU) track.

Purpose

The purpose of this standard is to describe the actions necessary to prevent track buckling and distortion caused by environmental temperature variations, by ensuring that:

a) rail is maintained stress-free at a rail temperature within the nominated range

b) track is maintained with adequate lateral stability

c) track is maintained adequately to resist fracture of rail or fishplates at low rail temperatures

d) maintenance activities during periods of high or low rail temperature do not jeopardise track stability.

This standard sets requirements for track monitoring and speed restrictions in hot weather.

This standard also includes the minimum action required in the event of a track buckle occurring.

Note: This standard is supported by G3206 'Track handbook 6 - Prevention of buckling' which may be referred to for further information and guidance.