NR NR/L2/SIG/11129 ISSUE 6 PDF

The requirements of this standard apply to electro-mechanical relays and electromechanical searchlight and banner signal mechanisms that perform safety critical or safety related functions and that form part of the infrastructure-based railway signalling control system.

Relays internal to electronic systems (e.g. pcb mounted reed relays) are excluded from the scope as these are covered by system maintenance and associated tests. Relays within signalling equipment (e.g. token or block instruments) are included and may require the entire unit to be replaced.

Searchlight and banner signals with only optical components and no significant moving parts, e.g. LED, fibre-optic, are excluded.

NOTE New relays shall be used on all new schemes.

Purpose

This standard details the requirement to control the risks presented by failures of signalling relays and electro-mechanical searchlight and banner signal mechanisms.

The aim of life management, as it relates to signalling relays, searchlight and banner signals performing safety critical or safety related functions, is to check that equipment continues to operate within its specified parameters.

Relay replacement/servicing shall be considered as part of the renewals programme as it is a life extension activity. However, some applications will require periodic maintenance servicing of particular relays to demonstrate safety.