Session 2

Signalling Diagrams, Sketches and Plans.

Objectives:     At the end of this session trainees will be able to:

·        Recognise the most common symbols used in railway signalling diagrams, sketches and plans.

Many of the symbols used in electrical circuitry are common to those used in railway signalling diagrams. Many however are not. Both are explained in this session. Of particular importance are the relays used and again terminology used in railway signalling is very different to that used in other electrical industries. The different types and functions of relays are explained from basics and the terms used for contact and contact arrangements are explained. For sketches and plans the symbols used are of course railway specific and are covered in this session.

Session 3       

Basic Signalling and Lighting Circuits

Objectives:     At the end of this session trainees will be able to:

·        With the use of diagrams, be able to describe the method of operation for main and other commonly used signals.

In this session circuitry used to operate signals and route indications are explained. Starting from the very basics, circuitry is gradually built up to explain aspect sequence, including signal ahead proving, to the more complex controlled signal circuitry. The basics circuitry of approach locking is explained at this stage. Circuitry used to operate junction indicators and other route indicators is then explained and finally shunt signals, subsidiary signals and banner repeating signal circuitry is explained.

Session 4       

Track Circuits

Objectives:     At the end of this session trainees will be able to:

·        Describe the method of operation and characteristics of A.C and D.C. track circuits.

Track circuits detect the presence or non presence of a train on a section of track and as such play a very important role in signalling systems. Although there are other devices to detect the presence or non presence, track circuits are the most common device used for this purpose. The basic track circuit is a very simple circuit but the characteristics such as relay voltage, ballast resistance, relay contact pressure and most importantly the drop shunt can be seriously altered by contrasting weather conditions. All of these characteristics are carefully examined. Another consideration to be taken into account is the presence of electrical traction systems used to operate trains. There are 2 types used covering a large part of the rail network. The overhead line system operates at 25,000 volts A.C. with the conductor rail system using a third rail and in some cases a fourth rail operates at 650 to 750 volts D.C. In both cases the running rails are used as part of the return circuitry. Trainees are made aware of the types of track circuits employed in these areas and are taught both traction systems and the most common track circuits used. This involves both D.C. track circuits and A.C. single and double rail track circuits.

Session 5       

Points

Objectives:     At the end of this session trainees will be able to:

·        Describe the method of operation of electric point machines and rail point clamp locks.

This session starts with the component parts of a point layout including stock and switch rails, stock rail gauge tie (sole plate) and stretcher bars. Trainees are then introduced to the three methods employed by NetworkRail to move point switches, mechanical, electro-mechanical (point machines) and electro-hydraulic (rail point clamp locks). The fundamentals of mechanical points are explained including facing point locks and detection and then it is explained how these operate, including basics of operation and fittings, within point machines and rail point clamp locks.

General

Throughout the conventional course trainees are given tests to prove progress and home work (approx ½ hour) is given at the end of each of the first 4 days which is checked the following morning as a group exercise.

Although trainees are encouraged to make their own notes should they wish to do so, a course folder is provided to contain detailed notes covering all 5 sessions. These are handed out at relevant points throughout the course and converts into an 81 page dossier of the course content.