scope:

This document applies to electromechanical relays that form part of the infrastructure based railway signalling control system which are used in safety critical or safety related applications. Additional information will be added as necessary to align this document with the special instructions referred to above.

It does not address the general personnel and system safety measures necessary for working with signalling equipment.

Purpose

This document has been prepared to summarise problems affecting railway signalling relays used on Network Rail's Signalling Infrastructure.

It is anticipated that this document will develop to become a controlled repository for providing advice and information on signalling relay problems. This document should be read in conjunction with any other issued special instructions requiring action to be taken with certain types / manufacturers relays or relays which have been serviced between certain dates. This document seeks to clarify, and assist with the identification of, those conditions identified as requiring special attention.

Any problems identified through special investigation, or brought to the attention of the infrastructure owner by other means will be risk assessed and, where required, specific instructions will be produced detailing the action required.