Question

Assessment 5.0: Ensuring fitness for purpose of the signalling system 5.1 Produce a report (300 words min) that explains how the sequential stages of installation, testing and commissioning of a new signalling system ensure it is fit for purpose. Your report should focus on the individual stages and the competence and equipment required and how the results of activities are recorded to be passed on to the next stages.

5.2 Produce a report (300 words min) that describes the need for maintenance, maintenance cycles and consequences of failure if maintenance is not carried out correctly

Answer 1

Fitness of a signalling system can be ensured

• If a particular section of track is occupied by a train that can be detected by Manual Detection,Track circuits and axle counters These are the function of a train detection sub system .

Mechanisms for point operating-:

• Switches of railway track ,that is movement of particular set of point from one place to another
• Provide security for the passage of trains by physically locking it in that position.
• Correct position is checked and locked.

Signal installation Stages

1. Remove existing signal head ( lens and incandescent bulb assembly) in the field
2. Rheostat (variable resistor) is set to zero or remove completely
3. To ensure the voltage corresponds to the system voltage,check the label on the back of the LED module. This is required for voltage settings
4. To help identify the color of the signal when it is off,the module wires have been color-coded For example, green signals have green wires
5.   LED module is inserted into the external ring holder, or LED module is inserted into lens slot and tighten metal tabs
6. Elimination of risk of electric shock .

Safety system:

It can lead to a disastrous event when a train driver fails to respond to a signal. Regarding this,various auxiliary safety systems have been devised.When the occurence of event like signal being passed at danger (SPAD) some systems start working.To supplement the lineside signals, audible and/or visual indications inside the driver's cab are included. If driver fails to acknowledge a warning, automatic brake application should be applied. The most sophisticated systems provide continuous supervision but some systems act intermittently

Signal testing is done on:

• Power systems,Token and block systems,Track circuit alterations and replacements,Point conversion work,Junction re-modelling and relaying,Level crossing upgrades and renewals,Train protection warning systems (TPWS),Panel and remote control systems , alterations and renewals,Processor based interlocking systems,Transmission systems,Correlation and survey works