NR NR/SP/ELP/27200 ISSUE 2 PDF

Purpose

The design of overhead equipment is based on the assumption that the geometrical relationship between the contact wire and the pantograph will be maintained at all times within agreed tolerances. Variations in this relationship infringing the agreed tolerances can lead to loss of contact or to infringement of electrical and mechanical clearances between pantographs and fixed structures and, in extreme cases, to pantographs touching fixed structures.

Assuming that the relationship between the contact wire and its supporting structure is fixed, the correct pantograph/wire relationship must be ensured by establishing and monitoring the relative positions of the supporting structure and the track. For this purpose, markers are provided on the fixed structure and it is the duty of P-Way and E&P staff to ensure jointly that the track remains in the position specified by those markers, subject to defined tolerances.

It is the purpose of this Instruction to define those tolerances, to describe the two types of markers and specify the agreed procedures for installation and checking. It will be circulated to appropriate members of the P-Way Engineering staff, as well as those of the E&P Engineering, with the intention of obviating any misunderstanding between the two departments.