scope:

Issue 4 of this SIN applies to all compatible designs of switch diamonds that are operated by compatible point operating equipment that fall within the phase 3 as shown in clause 7.

Purpose

This SIN covers the installation of the new tubular stretcher bar in existing switches as part of a programme to reduce risk.

The tubular stretcher bar has been developed to replace both 'fixed' and 'adjustable' stretcher bars in new and existing installations.

The majority of switches on Network Rail infrastructure use either 'fixed' full depth stretcher bars (known as 'black' or 'yellow' bars) or 35mm square 'adjustable' bars (often referred to as an '814 or 'adjustable' bar).

Fixed and adjustable stretcher bars are known to suffer from accelerated failure when subjected to repeated flange back contact or high drive forces usually as a result of overdriving with electro-mechanical Point Operating Equipment (POE). The tubular stretcher bar has been designed to eliminate these failures and reduce risk.

The more modern types of POE such as Hy-drive and HPSS have their own designs of stretcher bars and are outside the scope of this SIN. NR/L2/TRK/6100 specifies the use of the tubular stretcher bar in S&C renewals and maintenance tasks such as the replacement of half sets of switches, re-gauging or when replacing defective stretcher bars.