NR NR/SIN/106 ISSUE 1 PDF

This SIN shall apply to all RT60/NR60 Switches where the static gauge between the end of the planing and the first fixed baseplate is 1423mm or less.

Background and purpose

Inspection has highlighted problems with switch rails in RT60 & NR60 S&C failing to retain their designed curvature or straightness between the end of the planing and the first fixed baseplate. This is visually apparent on site either as a distortion within the switch on the through route, or more commonly as a straightening of the switch on the turnout route. In both cases the distortion / straightening leads to tight static gauge between the end of the planing and the first fixed baseplate and can affect the performance and reliability of the Point Operating System. In extreme cases this tight gauge has been reported to be low as 1420mm.

Investigations are continuing as to why this occurs, seemingly at random in a small percentage of the population of CEN60 switches but does not occur to the same degree in similar CEN54E1A1 switches installed in Vertical shallow depth S&C.

At some locations the measured static gauge is below the minimum permitted in the standards (1426mm), however, under traffic the switch rail moves dynamically to the point where the minimum gauge is achieved.

Whilst investigations continue the following actions are required to replace the worst affected switches.