S & T Notes - issue 136
S & T Notes - issue 136
SIGNALLING NOTES - Chris. Hall
Panic has set in this time! The last magazine appeared before I had
even started to collect my thoughts for this article. Normally I
have got at least a few pages of manuscript notes ready, sometimes
even typed up ready to submit. The magazines must be getting more
regular (or perhaps my copy for the last one was delayed). I am
writing this in early May but only having to cover the period
from the end of February. We don't exactly have a lot that must
be done in February/March/April - the train service is fairly light,
the weather unfriendly and the days short. A quick look at the
maintenance schedule shows that our now well-established maintenance gang
is keeping well up to date with the routine oiling, cleaning and
greasing of equipment.
A day in the life of the S&T
As the notes cover only a short period I thought I would focus
on a couple of days over the Easter weekend and describe the S&T
activities that took place. My lift to the railway on Thursday
evening failed to materialise so I drove up on Good Friday morning
knowing of two faults that had been reported on the Wednesday. On
arrival at Bewdley I checked the fault line (300) but the only new
message was for the Telecom. section of the Department.
I wrote the defect onto the
log in the telephone exchange with the date and time it was left and
this will be crossed off once it is repaired. One of the faults I was
planning to look at (Bewdley North Down Main Home Signal slow to
replace to Danger) obstinately refused to present itself so I signed
the Train Register Book in accordance with Rule 77A(ii) and went
out to examine the electrical detection on the 'B' end of 6 points,
which had been reported as not always making up first time. Confirming
that "there was a suitable opportunity between trains to enable the
work to be completed without detriment either to safety or train working",
I was able to effect a repair without the need for a disconnection. After
bringing the paperwork up to date (all S&T work at a particular box
is either recorded on a schedule of routine maintenance or in the defect
maintenance log held in the signal box locking room) and adjourning for
lunch, I noted that F.P.L. and detection testing at Bewdley South was due.
Detection testing at South is demanding as any single adjustment for example
affects the operation of more than one signal on the points concerned.
However the regular routine testing has meant that much of the equipment passes
the routine test first time. From the signalman's point of view, unless he
has seen it before and understands it, he is being called upon to
carry out an apparently pointless sequence of lever movements.
From the S&T technician's point of view it all appears so obvious - he
is standing by a switch and needs to trap a gauge between switch and stock
rail and get the signalman to try the signal (or F.P.L.) to see whether it
is free to operate or (depending which gauge is used) correctly prevented from
being operated. This may well have to be done many times and was convenient
revision of the locking of the frame for a trainee signalman whose exam was due
on the Sunday.
To illustrate the complexity of the task, I have shown the sheet I use to
capture the results of the testing. Each blank in the table needs to have
the test result recorded, so there are 24 boxes to fill in, some of which
require many lever movements. Detection testing at South takes all afternoon and
identifies four sets of detection requiring a small amount of adjustment.
The Signalman then asked how often the testing was done. The riposte
"it's scheduled to be done again on Sunday" got a wry smile - the testing
is actually scheduled every six months. By now it is 5:30 p.m.
and my colleague has arrived, apologetic that the lift had fallen
through. The Down Main Distant had failed in the Caution position part way
through the day (which needed two people to investigate) and we therefore
walked out to the location cupboard to confirm whether the correct electrical
signal was being given to the signal machine.
We found all in order at ground level and so resolved to take a ladder out the
following day. Many thanks to the North and South box signalmen for staying on
an extra half an hour at the end of the day so that we could decide whether the
problem was in the signal machine or not. Everyone had gone by now, except us
and the locomotive crews and cleaners so we adjourned for refreshments and food.
The next morning we were consuming a filling breakfast at Bewdley when someone
called out: "Is there anyone from the S&T here?" - immediate denials
were to no avail but the problem appeared to be one for the Telecom. section
(phones not working at Arley) and the Head of the Telecom. section (Steve Bradbury)
was immediately despatched. In fact this turned out to be a complete loss of power supplies
to Arley box due to a newly installed earth leakage circuit breaker which hasn't been
the same since it was struck by lightning. This was reset and the telephone difficulties
were traced to a cable fault between Highley and Hampton Loade which had been reported
on the previous day. Investigation into the fault showed that a culvert collapse at
milepost 144½ in Alveley Woods had caused cable damage. Subsequently the token
circuits were also affected which has prevented Hampton Loade from being switched in since
23 April but still allowed normal working on short section tokens. We recognised that there
was no guarantee that the remaining circuits in the cable would remain intact and that
in the event of any further failures in the cable Pilotman working between Hampton Loade
and Highley would be necessary until a repair could be effected. We advised the Traffic
Manager of this so that the necessary preparations could be made but as we are now into
the mid week running season he was not able to grant a day time possession. We will
simply have to wait therefore until the day when a Pilotman cannot be found or the fault
gets worse. This was resolved at the beginning of May when the cable failed completely
and we will do a repair at the next opportunity.
We cadged a lift on the 11:0 a.m. light engine 34027 Hogwart's Express with
a ladder to the Down Distant. We examined the signal machine, checked and exercised the
linkages and the signal machine sprang into life. With the fault apparently rectified,
we walked back to Bewdley with the ladder and
were surprised to see a class 50 charter heading north - the railway was busier than
we thought! After putting the ladder away, we made the necessary adjustments to the
detection at South (even more lever pulling because after each adjustment all the detection
on the affected switch has to be retested). Adjourning to the box for tea each time
the signalman wanted to let some trains pass, we discovered that the DMU was about to
be given a test run to Highley. The diesel engines had been overhauled and all six
engines were now operational, but had not yet been tried together. We decided that
a routine check at Highley would be sensible so, completing the work on the detection,
we went to platform 1 to adopt the posture of hitchhikers, successfully hailing the DMU,
which had to stop to pick up a token. Rule 9 applied twice in one day is unusual!
We had a brief discussion with Dave Wittamore who had been transferring tokens
between Hampton Loade and Highley and we agreed to meet later to discuss the forthcoming movements
of a certain canal boat (most of the S&T staff enjoy canal boating and drinking real ale).
The canal trip in question was a journey from Stourport to Shardlow - the trip was interrupted at
Loughborough for a visit to the Great Central. We paid a visit to Rothley and Loughborough signal
boxes and were most impressed with the installation. We met our S&T counterparts who showed
us around Loughborough box, relay and locking rooms. The double line section between Rothley
and Loughborough is worked under absolute block regulations with break section
boxes at Quorn and Swithland being worked upon. Whilst waiting at Arley for the
Up Passenger we interrogated the
signalman there "just in case there might be a problem" and were told the detection on the
Up Home Signal (no. 24) was proving troublesome. We had adjusted the detection on the yard
points recently so went straight out to the loop points at the north end. We found the
fault, tightened
and adjusted the detection and rather optimistically walked back to catch the 2:47 p.m. Down.
Missing it by a whisker, we decided to do the routine testing of the detection, which would
require some swift footwork as the introductory driving school was booked to shunt into the
Yard (3:4 p.m.) to permit a class 50 saloon special ("Hoover special") to pass the 3:28 p.m.
Up Passenger. The driving school was then booked to run round and be ready to depart southwards
when the next Down Passenger (which we wanted to catch) arrived at 3:59 p.m.. We completed the testing
(including the paperwork) with a few minutes to spare and caught the 4:2 p.m. Down. This was
the last train that we could catch to visit the bar at Bridgnorth, our day's work now being complete, and
still get back to Bewdley. So far the Department's average response time to faults was looking
good: BN5/6B - 2 days; BS0 - same day; BS detection - next day; telephones - 1 day; AY detection - same day;
token transfer - few days, with six people working on three different jobs in parallel on the
Saturday.
Because the S&T is the only remaining Engineering Department that does not use
full time staff or contractors for the service it provides (or have staff available on call),
it could be up to 5 days before a response could be provided. In fact almost all S&T
equipment failures (not that we have many, of course) have to be coped with by the Operating
Department by applying the provisions of the Rule Book. Although this may mean a
short delay (e.g. obtaining a handsignalman) the design of the equipment means that
safe operation can take place without having to wait until a repair can be arranged.
After all, S&T attendance may depend on staff driving long distances
if no-one from the S&T happens to be on the railway or available locally.
Other jobs that deserve mention are a major job to sort out the south end points at Highley
where the pedestal cranks beneath the frame had worked loose and were moving on the timbers
causing lost motion in the rodding run to the points. We had been asked by the Signalling Manager
(Operations) to try and repair these points because he was doing a box exam the following day
and felt this would be an unnecessary extra burden. Tony Neath's expertise with things
mechanical enabled us the leave the points in good working order. At Arley the drive to number 14
points (yard points) failed on the Sunday of the diesel gala causing the last trip of the DMU shuttle
between Kidderminster and Arley to be cancelled. We disconnected the ground signal reading into
the yard (number 19 signal) to maintain safe working. Following much encouragement from the
Chairman of the Operating Committee and others the Department has moved the Down Loop Advanced
Starting Signal at Kidderminster (number 58 signal) one pace left. Well it was actually about
6" or 8" constrained by a water pipe to the carriage shed. Limited clearance instructions will
therefore have to apply to movements in and out of carriage siding number 1.
Sequential locking
A rather simpler feature to describe this time. Signals giving permission
for trains to enter a block section (section signals) are usually provided
with electric locks that prove that the train has been accepted by the box
in advance before the lever can be pulled. The signals in rear however
could be replaced to Danger and subsequently cleared again with the section
signal inadvertently left in the 'OFF' position. This would allow the controls
on the section signal to be effectively bypassed. Sequential locking is therefore
normally provided on signals in rear, either by means of mechanical locking (which
ensures that the home signal lever cannot be pulled once it has been replaced, unless
the section signal has been replaced but, unlike other mechanical locking, does not
apply the converse) or electrical controls (which prove the section signal lever
or arm in the 'ON' position before releasing the home signal lever).
The mechanical locking is arranged so that the locking is driven by spring
assistance and engages as the home signal is replaced. It is released (and held released) as the
section signal is replaced but does not release the home signal lever until the electric
lock on the section signal should have engaged. Sequential locking thus ensures
that once the Home Signal is replaced to Danger, it cannot be lowered again until the section signal
has been replaced to Danger. Mechanical sequential locking is provided at Highley and electrical
sequential locking is provided at Bridgnorth, Bewdley North and South and Kidderminster. One
further electrical control can then be provided to prevent permission being given for a train
to approach from the box in rear unless the Home signal is at Danger (once given, the
permission is maintained if the Home Signal is subsequently lowered) - this 'home
normal proving' has so far been provided at Arley (not yet brought into use), Bewdley North (down),
Bewdley South and Kidderminster.
Point FPL Detection N R N R 12B/10A 31. 32 28. 29 10B 3 4 12A/13A 7. (14w12N) 6. 9 13B 25 24 15/16 7. (14w15N) 17/18A 7 (14w17N) 18B 19 21 5. 20 22/23A 5. 6 9. 20 23B 26 Notes: P - pass F - fail T - tight.