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Post by railtechnician on Sept 1, 2013 12:21:51 GMT
The IMR / relay room is adjacent to it (the air con that can be partly seen on the wall is in the IMR / relay room). Because of the nature of the equipment, especially when there is an interlocking frame involved (such as in an IMR) means it's preferable to keep these places as dirt and dust free as possible and they are usually sealed to a certain extent. Many of the IMRs were fitted into existing spaces and can be very cramped. Even those that were purpose built can be very cramped. There is a lot of equipment in them, mostly electrical and much of it with live connections, with barely enough space to walk between the racks. Not the best sort of place to be wandering around with a feather duster Some IMRs are extremely cramped but these days anything dangerous is covered up, we did that under EWA copmmencing in the late 1990s. Indeed I ran a workshop at Acton Town where I had a gang of fitters making covers for fuse bays, transformers and other exposed items in IMRs and relay rooms which they surveyed and then fitted out. However, IMHO it was a mistake to let every Tom, Dick and Harry have access to such rooms. Trained staff knew what was dangerous and were trained to do nothing without instruction including leaning upon anything or touching anything without permission. There were a number of incidents where cleaning contractors, other external contractors and untrained staff of other LU departments caused signal failures when given keys to signal equipment rooms. I have always thought that untrained and unqualified staff of any rank should not be allowed anywhere near such places unless accompanied by a licensed and competent person. Of course a license alone is not a guarantee of competence but it does suggest that an individual has at least had training and thereafter really ought to be held personally accountable for any and all actions as used to be the case long before the days of licensing when I joined LT. The biggest danger to be found in an IMR is 'an idiot' !
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Post by Nortube on Sept 5, 2013 10:53:46 GMT
Many years ago (and before the monstrosity blocked the platform view), I and several others saw all three platform starters at Morden go green. Impossible I know, and I was shown the wiring (book) diagrams by the Morden AET to prove it couldn't happen, but it did. If others hadn't seen it as well, I'd have thought that perhaps I'd been mistaken. However, the IMR was being worked manually that day due to loss of control from Cobourg Street for whatever reason and there were various people in there, including a Signalman and AET. Who knows what was occidentally touched inside there.
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Post by railtechnician on Sept 5, 2013 11:47:45 GMT
It's years since I've been to Morden, late 1980s commissioning the trial Vic line train radio system that we installed between Colliers Wood and Tooting Bec. I can recall three or possibly four crossovers there and without seeing the bookwiring I'd say it was impossible to get all three starters clear simultaneously even with a wrong side failure, I'd have said that more than one such failure would need to occur coincidentally. Either that or a very irresponsible and wilful act which would require more than a little thought. On the other hand it is amazing what mischief a contact fault in a cable can cause even though circuits are carefully routed and always paired with their mating returns. Having said that I am well aware of situations in old lead cabled sites where wiring wasn't exactly as shown in the prints laying undiscovered for years and where a simple earth fault could result in 'impossible' failures'
It's hard to try and guess the scenario without seeing (a) the bookwiring circuits (b) the locations of the relevant circuits to outgoing fuse bays and their geographical proximity (c) working out exactly what would be required to successfully illuminate three conflicting route green lights!
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Post by Nortube on Sept 5, 2013 14:51:20 GMT
All points are normal when the starter on platform 5 is green, platform 3 starter has one point that has to be reverse, platform 2 has a single point and a pair of points that have to be reversed. I'm not sure if any points were actually reversed and I can't remember what starter eventually went to green to allow the train movement. (Initially, after all three were green, they all went back to red). I did wonder if it was a multiplexing thing that gave the optical illusion of all three being green, rather than just one in turn but, all things being equal, the relevant route would have to be set up in each case and no way were the points going to be reversed and detected then normalised and reversed for the next platform etc. in the time it would take for the multiplexing effect not to be seen.
It was safe, in so much as (as far as I know) the trainstops remained up (no dual aspects that I recall) and the fact that the three greens were only on for around ten seconds before all going to red again so the trains wouldn't have moved in that time as the doors wouldn't have had time to close. It was very strange and something that nobody had an explanation for.
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Post by railtechnician on Sept 6, 2013 8:39:57 GMT
There is no such thing as multiplexing in safety signalling, whereas just about everything is multiplexed on the non-safety signalling. Safety signalling circuits are individual to the extent of using individual contacts of a relay for each circuit when one contact could be placed in more than one circuit to achieve the same functions. In the same way common armature contacts (changeover contacts) are rarely seen (UECR and delta.Rs are examples) with track circuit, point and signal control relays using independent make and break contacts giving better failsafe circuitry. In order to illuminate three signal DEs simultaneously three GQ lines would need to be bridged. The most obvious place would be at the outgoing fuse bay and the three circuits would have to be adjacent to one another. AFAIR this would only be the case in a really old room and even then one would expect to see the BX (feeds) legs separated by the associated NX (returns) legs such that leaning across the circuits with any kind of conductor would more likely cause short circuits and blow the fuses rather than feed three lamps in parallel from the one selected lamp.
As I said it's difficult to speculate especially when considering just how much thought goes into signalling circuit design and layout of equipment and fuses to minimise the risks of wrong side failure and to ensure the best possible failsafe conditions to mitigate, if not eliminate, all but wilful interference.
It's the sort of problem or issue I would pose to signal apprentices when giving them 'field training' testing out in IMRS on night shift.
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Post by hellocontrol on Sept 6, 2013 9:50:43 GMT
Many years ago (and before the monstrosity blocked the platform view), I and several others saw all three platform starters at Morden go green. Impossible I know, and I was shown the wiring (book) diagrams by the Morden AET to prove it couldn't happen, but it did. If others hadn't seen it as well, I'd have thought that perhaps I'd been mistaken. However, the IMR was being worked manually that day due to loss of control from Cobourg Street for whatever reason and there were various people in there, including a Signalman and AET. Who knows what was occidentally touched inside there. I have seen quite a few strange things with signals over 40 years, all of them I was told could not happen but they did and investigations were carried out the results of which were kept amongst those that had a need to know and we were all told to forget what we had seen. There are three which I will mention the first was on the Picc line at Earls Court just after re signalling a train was on the EB homes and after they had cleared so did the starter just one thing there was a train ahead only just left the platform. Second one was on the Met at Baker St there was a train in the SB city platform with a train on the SB homes T/Op used the SPT and the signalman said that there was a train ahead to which the T/Op replied yes I know that but why are all the signals between my train and that one showing green. The area had just been re signalled. And the third on the Vic line at Brixton train in the SB platform starter green to go north 420 code just one thing the points were still set for the SB road (all normal) we all dared the T/Op to close the doors and press the start buttons but he did not.
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Post by Nortube on Sept 6, 2013 13:15:37 GMT
For safety reasons, I didn't expect that side of it to be multiplexed, but that was the only very unlikely other explanation I could think of that would account for three greens or seemingly three greens whereas in fact only one may have been lit at any one moment. hellocontrol Another well documented incident was on the District line many years ago at Charing Cross (now Embankment) where human error caused signal(s) to remain green or clear too early. It was reported by a driver, but was ignored. A train later crashed into the back of another as a consequence. Just done a quick google and found the details: [ Click here ] Wiki [ Click here ] MoT report
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Post by railtechnician on Sept 6, 2013 15:06:10 GMT
I have seen quite a few strange things with signals over 40 years, all of them I was told could not happen but they did and investigations were carried out the results of which were kept amongst those that had a need to know and we were all told to forget what we had seen. There are three which I will mention the first was on the Picc line at Earls Court just after re signalling a train was on the EB homes and after they had cleared so did the starter just one thing there was a train ahead only just left the platform. Second one was on the Met at Baker St there was a train in the SB city platform with a train on the SB homes T/Op used the SPT and the signalman said that there was a train ahead to which the T/Op replied yes I know that but why are all the signals between my train and that one showing green. The area had just been re signalled. And the third on the Vic line at Brixton train in the SB platform starter green to go north 420 code just one thing the points were still set for the SB road (all normal) we all dared the T/Op to close the doors and press the start buttons but he did not. The first incident may not have been an incident at all, it rather depends upon the actual position of the train at the homes, whether the starter was on a shortened overlap (slotted signal) or not and just how quickly the driver of the train that left the platform had accelerated away. To be honest I cannot recall any on the Picc but Earls Court was one site where I seldom did signal maintenance in the Picc tunnels although I did plenty of other work there. Of course it's pointless trying to speculate if it was indeed a wrong side failure with no clues and no 'prints'. There are plenty of places on the network where apparently strange events are/have been seen but predominantly the signalling is working to design specification. I think I have an idea about the Baker Street incident if it is the one I am thinking of, the morning after the resignalling changeover, I was on that job although at the time I was comms and in the IMR all night. The outcome was that trips for platforms 2 & 3 signals were close to one another in the 6 foot and somehow the 'snakes' had been transposed during the changeover meaning that platform 2 trainstop remained OFF. However, I know no more than that. Baker St IMR was the site of vandalism and had to be rewired after person or persons unknown took a hacksaw to the internal wiring just as the room was nearing completion and so it may be postulated that it was not the only act of vandalism alleged to have taken place by disgruntled signal staff. I can't speak to the Brixton event, I seldom if ever worked on Vic signalling, in any case I was only a lowly wireman when I did, although I did plenty of other work at every station on the line. The wrong side failure that has always stuck in my mind was immediately following the first Wood Green resignalling (1978 IIRC) when we took out the cabin with a temporary relay room built on the eastbound platform between the cabin and the running office and transferred control to Arnos Grove. We had completed the changeover and most of the 100+ changeover staff had returned to depot, a few of us were still on site because the new fangled electronic TD wasn't working and we were standing by when the first Sunday morning reverser arrived. Passengers were detrained, the doors closed and the train took the route to the siding quite normally but then promptly disappeared from the relay room diagram leaving the track over the points down and the points tracklocked. Very quickly trains were backed up even though it was a Sunday morning and the depot chief, who was still on site, and my guv went to investigate, clipping and scotching the crossover normal after taking possession. It was fairly quickly established that F & G track incoming cables had been transposed on the temporary relay room fuse bay as there was clear evidence on the ticket strip (what we used to use for temporary fuse bay labels until the ordered traffolyte labels were delivered). It was never discovered who changed the labelling or why it was done without request for further tests to prove the cables but it seemed to have occured when the track dropping board (which we used to use to simulate train movement during the changeover) was installed by the day staff who wired the room. On nights we were wiring all the new trackside equipment and 'plate racking' existing circuits. We were the last crew on site prior to the Saturday night changeover and as a result my guv was 'run' and was 'dropped' as blame always fell on the last man known to be in the room!
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Post by Harsig on Sept 6, 2013 19:56:19 GMT
I think I have an idea about the Baker Street incident if it is the one I am thinking of, the morning after the resignalling changeover, I was on that job although at the time I was comms and in the IMR all night. The outcome was that trips for platforms 2 & 3 signals were close to one another in the 6 foot and somehow the 'snakes' had been transposed during the changeover meaning that platform 2 trainstop remained OFF. However, I know no more than that. Baker St IMR was the site of vandalism and had to be rewired after person or persons unknown took a hacksaw to the internal wiring just as the room was nearing completion and so it may be postulated that it was not the only act of vandalism alleged to have taken place by disgruntled signal staff. I remember being told about this incident but was told that this was only related to the signals at the south end of platform 2. There are two signals there mounted back to back, A900 for trains entering platform 2 from the city and MB15 for trains departing platform 2 to the city. Their respective trainstops are, naturally enough, located either side of the same track and both in line with the block joint. It was my understanding that it was these two trainstops which became transposed and this would be quite difficult to spot in testing as for any movement past this point in either direction both trainstops must lower so that any train is not back tripped. It was only the timing and sequence of the lowering that was wrong and presumably could only have been detected by physical observation of the operation of the trainstops coupled with an understanding of the sequence in which they should have operated.
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Post by hellocontrol on Sept 10, 2013 7:08:12 GMT
I think I have an idea about the Baker Street incident if it is the one I am thinking of, the morning after the resignalling changeover, I was on that job although at the time I was comms and in the IMR all night. The outcome was that trips for platforms 2 & 3 signals were close to one another in the 6 foot and somehow the 'snakes' had been transposed during the changeover meaning that platform 2 trainstop remained OFF. However, I know no more than that. Baker St IMR was the site of vandalism and had to be rewired after person or persons unknown took a hacksaw to the internal wiring just as the room was nearing completion and so it may be postulated that it was not the only act of vandalism alleged to have taken place by disgruntled signal staff. I remember being told about this incident but was told that this was only related to the signals at the south end of platform 2. There are two signals there mounted back to back, A900 for trains entering platform 2 from the city and MB15 for trains departing platform 2 to the city. Their respective trainstops are, naturally enough, located either side of the same track and both in line with the block joint. It was my understanding that it was these two trainstops which became transposed and this would be quite difficult to spot in testing as for any movement past this point in either direction both trainstops must lower so that any train is not back tripped. It was only the timing and sequence of the lowering that was wrong and presumably could only have been detected by physical observation of the operation of the trainstops coupled with an understanding of the sequence in which they should have operated. I think that was another incident, the one I mentioned took place just after the new signalling was commissioned and the T/Op could see all the signals from where he was to the platform and they were all green.
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Post by hellocontrol on Sept 10, 2013 7:13:33 GMT
I have seen quite a few strange things with signals over 40 years, all of them I was told could not happen but they did and investigations were carried out the results of which were kept amongst those that had a need to know and we were all told to forget what we had seen. There are three which I will mention the first was on the Picc line at Earls Court just after re signalling a train was on the EB homes and after they had cleared so did the starter just one thing there was a train ahead only just left the platform. Second one was on the Met at Baker St there was a train in the SB city platform with a train on the SB homes T/Op used the SPT and the signalman said that there was a train ahead to which the T/Op replied yes I know that but why are all the signals between my train and that one showing green. The area had just been re signalled. And the third on the Vic line at Brixton train in the SB platform starter green to go north 420 code just one thing the points were still set for the SB road (all normal) we all dared the T/Op to close the doors and press the start buttons but he did not. The first incident may not have been an incident at all, it rather depends upon the actual position of the train at the homes, whether the starter was on a shortened overlap (slotted signal) or not and just how quickly the driver of the train that left the platform had accelerated away. To be honest I cannot recall any on the Picc but Earls Court was one site where I seldom did signal maintenance in the Picc tunnels although I did plenty of other work there. Of course it's pointless trying to speculate if it was indeed a wrong side failure with no clues and no 'prints'. There are plenty of places on the network where apparently strange events are/have been seen but predominantly the signalling is working to design specification. I think I have an idea about the Baker Street incident if it is the one I am thinking of, the morning after the resignalling changeover, I was on that job although at the time I was comms and in the IMR all night. The outcome was that trips for platforms 2 & 3 signals were close to one another in the 6 foot and somehow the 'snakes' had been transposed during the changeover meaning that platform 2 trainstop remained OFF. However, I know no more than that. Baker St IMR was the site of vandalism and had to be rewired after person or persons unknown took a hacksaw to the internal wiring just as the room was nearing completion and so it may be postulated that it was not the only act of vandalism alleged to have taken place by disgruntled signal staff. I can't speak to the Brixton event, I seldom if ever worked on Vic signalling, in any case I was only a lowly wireman when I did, although I did plenty of other work at every station on the line. The wrong side failure that has always stuck in my mind was immediately following the first Wood Green resignalling (1978 IIRC) when we took out the cabin with a temporary relay room built on the eastbound platform between the cabin and the running office and transferred control to Arnos Grove. We had completed the changeover and most of the 100+ changeover staff had returned to depot, a few of us were still on site because the new fangled electronic TD wasn't working and we were standing by when the first Sunday morning reverser arrived. Passengers were detrained, the doors closed and the train took the route to the siding quite normally but then promptly disappeared from the relay room diagram leaving the track over the points down and the points tracklocked. Very quickly trains were backed up even though it was a Sunday morning and the depot chief, who was still on site, and my guv went to investigate, clipping and scotching the crossover normal after taking possession. It was fairly quickly established that F & G track incoming cables had been transposed on the temporary relay room fuse bay as there was clear evidence on the ticket strip (what we used to use for temporary fuse bay labels until the ordered traffolyte labels were delivered). It was never discovered who changed the labelling or why it was done without request for further tests to prove the cables but it seemed to have occured when the track dropping board (which we used to use to simulate train movement during the changeover) was installed by the day staff who wired the room. On nights we were wiring all the new trackside equipment and 'plate racking' existing circuits. We were the last crew on site prior to the Saturday night changeover and as a result my guv was 'run' and was 'dropped' as blame always fell on the last man known to be in the room! The Earls Court incident I seem to remember that someone said a piece of foil or something like that had gone across some contacts. The Brixton incident was only one of many some minor like the train stopping but there were no brake commands anywhere near normally in the Stockwell area. There were serious ones or should I say allegations because no one ever reported back and they were buried in the reports somewhere perhaps the offices at Acton where there was a book of reported signalling wrong side failures.
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