SVR S&T Dept.
SIGNALLING NOTES - Chris. Hall
The last article covered our activities up to the beginning of May. At this time of year the weather can cause us some difficulties. Our work on the south end points at Bridgnorth over the winter seems to have been successful and we have not had complaints of these points being difficult to operate during the hot weather (and we have had some days with very hot weather). However we did have complaints that the south end points at Hampton Loade were particularly difficult to operate. The track at this location needs repacking from time to time and the rodding run can get a bit uneven as the ground moves. The complaints though were unusually persistent and so the next day (18th June) we turned up in force.
It certainly looked like hard work as we asked the trainee signalwoman to work the points back and forth a few times and we examined the rodding run to see whether there were any obvious difficulties. None being evident, we asked for permission to disconnect the points - now it was clear what was wrong. In the hot weather one of the switch rails had expanded so that the expansion gaps were closed up and so much pressure was being exerted from the FPL stretcher to the FPL casting that the switches could barely be placed reverse. Other than report the problem to the Permanent Way Department via our Head of Department for urgent attention, there was little we could do as a rail would need to be cut and welded. These points had been renewed after a derailment a few years ago and the recent hot weather had resulted in sufficient expansion to cause these difficulties.
Although it is difficult to see, the FPL stretcher is pressing hard up to the FPL casting as the switches have expanded in the hot weather [Photo: J. Smith]
The weather - a mixture of heavy rain and strong sunshine - also tends to cause the vegetation to put on a spurt. We were not surprised to find complaints about the Up Distant at both Arley and Hampton Loade being heavy to pull and (at Arley) troublesome to get it to return to Caution. The P-Way had agreed to deal with Hampton Loade but we were going to Arley anyway to fit a handrail to the intermediate platform on the Down Homes and so we had a look to see whether it was just heavy vegetation lying on the wire run. We found that the embankment had fallen onto the wire run so that it was barely above the surface. We would need nearly a dozen signal wire stakes and pulleys to lift it up, clear of the ground. A make-shift cover had been added to hold back the earth in one place and this would have to be removed, making the job much more difficult. We cleared a lot of vegetation away but this would be a whole day job for the following weekend (and, therefore, the next article as the press deadline looms).
The problems with the track circuit indications between Bewdley South Down Distant and Bewdley South box have not gone away although we have been able to take some ameliorating actions, disconnecting Bewdley South Down Distant and utilising a spare core in the cable to parallel up a couple of circuits. The problem is a cable problem (they are over 30 years old), rather than the track circuits themselves, and before attempting the difficult task of fault-finding on the cable circuits bringing the track circuit indications from the location cupboards to the box, the first task is to refurbish the location cupboards, reterminating some cable ends. This is a slow job, between trains to ensure the minimum disruption to the passenger service.
The electrical power supply to Northwood crossing was disconnected when the supply cable was damaged: the effect this has on the crossing is that the battery back up continues to operate the crossing in all respects except that the Drivers' white lamp will not operate. The fault will then be reported by the crew as a failure. The local circuits to operate the crossing are completely self contained and the through cables simply pass by.
We continue to improve the arrangement of items in our stores building, particularly for electrical items on the new mezzanine floor. Routine maintenance remains a full time job for the paid staff. This includes testing back up power supplies, facing point lock clearances, detection and track circuits and maintenace of point rodding, signal wire runs, lever frames, point and signal machines. For example FPL and detection testing takes place every six months and is recorded on the maintenance schedule and detailed paperwork is kept up to date to demonstrate that the equipment remains in a safe condition.
A final reminder that this article, as well as other information on Signal Engineering, can be viewed in full colour here on the unofficial Signal Engineering web site.