scope:

This module describes the design of lever frames and associated interlocking. See also the mechanical handbook, NR/GN/SIG/19014.

Although this module is not in itself mandatory, use of mechanical locking will satisfy the principles given in Section 2 of this Part of the Standard if the appropriate sections are complied with. The application of the principles and requirements to mechanical and electro-mechanical interlockings are summarised in Sections 4 and 5, respectively.

The design details required for a mechanical interlocking are described in NR/L2/SIG/11201, Module A2. Examples relating to the typical layout shown in Figure:10 are given in Figures:11 to 14.

Most of the locking terms used in this Module are illustrated in the figures. Where other former regional terms are found describing these items, care should be taken to avoid ambiguity. For instance, locks and notches are also known as nibs (or wedges) and ports. Tappets can be known as swords, irons or blades. Locking bars can be referred to as bridles, and studs as drivers.

Purpose and introduction

This module forms part of the Signalling Design handbook (SDH: NR/L2/SIG/11201) and is to be read in conjunction with the other modules of the handbook and reference documentation.

This Network Rail standard contains requirements and guidance on signalling engineering applications. The content supports the specific and general requirements described in Railway Group Standards and the Network Rail Signalling Principles Handbook [NR/L2/SIG/30009].

NOTE Where there is a conflict between this standard and a Railway Group Standard or the Network Rail Signalling Principles Handbook [NR/L2/SIG/30009] then this standard shall not take precedence

Decisions made by a competent person should be supported by appropriate evidence or documentation.

NOTE Use of designer notes on drawings (see HSE CDM guidance) will generally suffice as may Design Log entries.

Any adoption of alternative solutions requires an assessment commensurate with the significance of the proposed change and which follows the guidance provided by the Common Safety Method for Risk Evaluation and Assessment [CSM-RA]; Network Rail's adopted method for the control of safety risks.