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| Track Circuits and sections of rail 23/10/2011 at 21:15 #21992 | |
UKTrainMan
1803 posts |
Do track circuits align with sections of rail or can one section of rail be split to form two or maybe more track circuits?
Any views and / or opinions expressed by myself are from me personally and do not represent those of any company I either work for or am a consultant for. Log in to reply |
| Re: Track Circuits and sections of rail 23/10/2011 at 21:23 #21993 | |
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TomOF
452 posts |
Yes, there are jointless track circuits available, Aster being a common type. Also axle counters allow for a track section to be split in the middle of a rail section.
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| Re: Track Circuits and sections of rail 24/10/2011 at 04:44 #21994 | |
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pilotman
189 posts |
Also there is a limit to the length of a track circuit, so if you want it really long one (e.g. on a long single line) it may be necessary to join 2 or more physical track circuits together to provide for this.The indication in a box or signalling centre will only show 1 circuit. Another reason for splitting is where complicated pointwork creates a requirement to swap the polarity of a tc., often in the middle of a platform. Ray Log in to reply |
| Re: Track Circuits and sections of rail 24/10/2011 at 12:36 #22006 | |
alvinhochun
249 posts |
Quote:Can one section of rail be split to form two or maybe more track circuits? All I know is that there must be additional equipment installed. Yes there are jointless TC, like using Axle counters or using DTMF tone (is that right? I remember it is used on DC catenary) And if some "physical" TCs originally joins to form a "logical" TC, it can be split. _ _ _ _，_ _ _ _！ (censored by the Hong Kong national security law) Log in to reply |
| Re: Track Circuits and sections of rail 24/10/2011 at 17:07 #22017 | |
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button_pusher
56 posts |
Depends what you mean by "split the rail." If you mean physically split up the rail then yes, this is most common type of track circuit. with the positive leg separated by insulated block/rail joints. These have a limit IIRC of 1000m though you can have as many indivdual track circuits cut into the track repeater circuits so the signaller only sees one indication on his panel (very common). On jointed track, to maintain the track circuit over fishplates, two galvanised bonds are used. If you mean on CWR, then glued IRJs are used on DC track circuits to split the rail up. Again, indivdual track circuits can be linked together via track repeater circuits. If you mean without the use of IRJs then you have: TI.21/Aster frequency based track circuits which you have 8 frequencies, A-H. Here you butt A and B frequencies together and at the track tuning unit they create a frequency "tuned zone" which create individual track circuits. These can be used via various permutations of trackside equipment to create track circuits of up to 3000m (again I'd need to check this). These track are characterised by the whistling noise from the white boxes strapped to the track. Axle Counters which are different to track circuits as the rails no longer carry a detection current. Instead they use transducers mounted each side of the rail which counts axles passing over it. When the train passes out of the section, a the related "heads" count the wheels out and the result is compared by an evaluator. I've not any experience with these so I've no idea how long a distance they can be used over (I'd assume signal attenuation would play a factor). There are many different types of track circuit/train detection in addition to the above mentioned ones and dependant upon the situation/purpose they are required to work in. Hope the above has answered your question (unless I'm on completely the wrong track...) button_pusher Last edited: 24/10/2011 at 17:11 by button_pusher Log in to reply |
| Re: Track Circuits and sections of rail 25/10/2011 at 15:22 #22030 | |
GeoffM
6282 posts 
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" said:Axle Counters which are different to track circuits as the rails no longer carry a detection current. Instead they use transducers mounted each side of the rail which counts axles passing over it. When the train passes out of the section, a the related "heads" count the wheels out and the result is compared by an evaluator. I've not any experience with these so I've no idea how long a distance they can be used over (I'd assume signal attenuation would play a factor).Theoretically no limit, as long as the heads/evaluators have communication links between them. Interestingly, axle counters can suffer from "short, fast train" syndrome if an axle counter head is connected to two evaluators ("in" and "out"), and the evaluators communicate to the interlocking over different links, then the outgoing evaluator can report clear before the incoming has reported occupied. SimSig Boss Log in to reply |
| Re: Track Circuits and sections of rail 26/10/2011 at 06:06 #22049 | |
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button_pusher
56 posts |
" said:" said:CheersAxle Counters which are different to track circuits as the rails no longer carry a detection current. Instead they use transducers mounted each side of the rail which counts axles passing over it. When the train passes out of the section, a the related "heads" count the wheels out and the result is compared by an evaluator. I've not any experience with these so I've no idea how long a distance they can be used over (I'd assume signal attenuation would play a factor).Theoretically no limit, as long as the heads/evaluators have communication links between them. I've not had anything to do with axle counters apart from a cursory perusal of the literature to have a look-see how they work! DC tracks are my bread and butter! Log in to reply |