does anyone have any examples of axle counter tables or any guidance on them at all? finding it really hard to get info on this. standards do not give very much.
|
axle counters CT Reset / Restore
|
09-11-2010, 08:57 AM
(08-11-2010, 10:30 PM)sgm1983 Wrote: does anyone have any examples of axle counter tables or any guidance on them at all? finding it really hard to get info on this. standards do not give very much. Do you mean for reset-restore, Engineering Possession Reminders, Special Train Reminders and the like? They are a nightmare and in my view well over the top. I assume you need to know for work purposes; as far as the IRSE Exam is concerned, don't worry about them- know the concept but don't get into the detail!
PJW
09-11-2010, 09:39 AM
sgm1983,
It'd be useful if you wrote a short precis of your axle counter understanding in this forum so someone can add to what you know and for others to read around the subject. Thanks in advance, Jerry
Le coureur
Peter
You are correct in saying yes I need it for my work. I am talking about EPR/STR and aspect restriction. I have looked at Newport and Edinburgh Waverley as an example but I am aware that the principles used are slightly out of date. I have also read 30080/30081/30082. These just do not go into the level of details I am looking for they are all very open statements which can be interpreted many ways. Eg what happens with distant auto sections etc? Jerry I have an understanding of what EPR STR. conditional and unconditional reset are but only have a minimal knowledge when it comes to the principles behind them. Any help or anyone who can point me in the right direction would be much appreciated
12-11-2010, 09:42 PM
(This post was last modified: 12-03-2018, 10:31 PM by PJW.
Edit Reason: replacing missing WORD by pdf
)
(09-11-2010, 07:21 PM)sgm1983 Wrote: Peter Oh the joys of non-prescriptive standards! Another thing about railway standards nowadays is that there are so many different ones to choose from! If you haven't already discovered them, suggest you look at the attachments in this module 5 post ; perhaps not really what you are after back some useful background. I also attach a summary of reset / restore produced for a YM exam event a couple of years ago that possibly only covers what you already know, but may be useful to you or others. I think it is fair to say that we have yet to achieve stability on a satisfactory methodology. It was the West Coast Route Modernisation that really set the standards of which you are aware, but yes there have been changes since in the light of experience / different projects and contractors getting involved. There is a tension between trying to make sure that a) the maximum protection is given against inappropriate reset and b) being able to restore the railway to normal working quickly and easily following any disturbance. Not only that but there are definite complexity costs in implementation- when this functionality is actually making serious inroads into the capacity of an electronic interlocking then one must wonder if the tail is wagging the dog! Newport is I think one of the most recent projects and therefore I'd certainly expect it to be different from Edinburgh for this reason, as well as the fact that there is a definite difference in the environment between long sections within plain line railway and short sections in complex areas and slow speed running. In addition Newport attempted to use a WESTLOCK to implement the size interlocking that would have taken 4 SSI; whereas that was a reasonable thing to do on the basis of a simplistic assessment, there are actually a host of different potential constraints. An SSI has the capability I think of 1024 latches (including the specific ones used for subroute and suboverlaps) but when WESTLOCK was being designed it was before the days of axle counter complicated reset-restore so consideration of the historic usage of various elements over many SSI schems suggested that this was never the constraint and hence the optimum tradeoff was a reduced provision of latches to increase other elements that were often at a premium historically. This meant that the designers then found that they had put too large an area into the one interlocking and had run out of latch capacity; I don't know the details but I wonder if this caused some re-evaluation of what was really essential ......... Therefore I certainly wouldn't like to give specific advice re completing Control Tables for them; I'd expect the project to have defined some standards dictating how they are to be completed. In essence the idea nowadays is generally to allow the signaller a) to reset the axle counter on their own authority, not involving a technician (as per cooperative reset), b) for this reset to take immediate effect (rather than being a preparatory reset that only restored the section after it had been traversed by a train). The reason for this is that immediate clearance of the track section permits points to be moved that would otherwise be locked. However we are not comfortable to permit a train then to traverse the section at high speed; there is a small but finite risk that the section was not actually clear and the reset was mistaken- the likelihood may be small but the consequences could be very high and thus the risk assessed to be unacceptable. Therefore the mitigation of not allowing the signal to clear to a yellow or better; given the fact that there are no POSAs provided in the vast majority of situations then the signal has to be held at red and the driver verbally authorised to pass it. Because the track section is itself showing clear, then in order to prevent the signal from clearing an additional type of locking has to be imposed. Basically each path over each train detection section is given a latch memory to register that the section had been reset and there has yet to be a train passing over it and therefore can't really be 100% certain that it really is clear. Once a train has passed then this element of Aspect Restriction is removed, but for a section with points there is still a possibility that the portion on the other lie of those points may actually still be harbouring an invisible obstruction so there has to be separate memory for that portion which won't be removed until there has been a train over that portion as well subsequently. There are various rules that say if the spur section is short enough / visible enough then it can be deemed to have been swept by a train taking the other lie of points, but in general separate trains will be needed. Then there is the possibility that although a train enters a section that it might not fully traverse its length since there may be a signal mid way at which is could have reversed before getting to the end. Since Aspect Restriction is normally taken off as the section becomes occupied, then there have to be special controls in such cases that this does not happen, just in case the train doesn
PJW
(12-11-2010, 09:42 PM)PJW Wrote:(09-11-2010, 07:21 PM)sgm1983 Wrote: Peter Thanks for the info Peter. Thanks for the info. I will post any more info I find out
15-11-2010, 10:06 PM
I have added some additional info that I believe to be correct. If anyone disagrees or has anything extra to add please reply
Thanks (15-11-2010, 10:06 PM)sgm1983 Wrote: I have added some additional info that I believe to be correct. If anyone disagrees or has anything extra to add please reply EPR / STR 1. "No reminder device on track section"; I think you mean "no reminder device applied on the reset function for the track section"- don't confuse this with EPR / SPR reminders. On a VDU this reminder is displayed as yellow bands either side of the track name, generally adjacent to the reset icon green roundel or applied to that roundel itself. Believe this may have been a signaller's responsibility for schemes such as Rugby-Nuneaton Note the wording of NR/L2/SIG/30081,6.5.7: The controls for removal of EPR from axle counter section shall test for any reminder on the reset roundel..... 2. Since EPR is to permit restoration without aspect restriction at the end of a possession, then obviously the protecting signals should be ARAFOAL when it is applied. So although it does not insist on proving reminder collars applied to the relevant signals, it does require them to be route normal. In the case of auto signals I think this requires the replacement facility effective. 3. Conversely wouldn't want to restore a track section at the end of the possession if it hadn't been clear before the start; hence the requirement that the track is showing clear before the EPR can be applied. 4. The EPR and STR are mutually contradictory (EPR for possessions and prevents main aspect clearance, STR for abnormal train in normal working and permits one clearance of main aspect) and therefore are locked against each other. 5. Not sure what the distinction re item 2. Main aspect clearance a) Need to make sure that the EPR are all removed before the resumption of normal service; hence proved in the aspect. b) Any ARFR segment imposes aspect restriction, so for clearance of main aspect then all must be unset. An indication is provided adjacent to the representation of each signal (on a VDU adjacent to the reminder collar) to give the signaller confidence that they may authorise the driver past the signal at danger whilst gaining the security of the interlocking. Hence this indication is given whenever the signal would be showing proceed if it were not for the application of AFRF. Hence I'd say when "a remider device is applied to the entrance and all aspect conditions are met except any ARFR set"; I think this is what you meant but my reading of your wording doesn't actually equate. Note that this indication permits the signaller to regard the signal as operational rather than defective which is significant in regard to the rules that apply when authorisng a driver to pass signal at danger. I think whether or not the interlocking is designed to prove that signal reminders are applied to entrance / exit signals is one of those items which have varied between schemes. Note the wording of NR/L2/SIG/30081,6.4.6: It shall not be necessary to design interlocking to enforce the application of reminder devices.....; this stops short of saying "don't". Obviously for a panel it is not practicable to enforce. The following section only requires Appropriate routes shall be proved normal in the interlocking when initiating a reset. ------------------------------------------------------------------------------------------------------------------------------ Some hints follow re the completion of the various axle counter Control Tables; note that projects differ in precise headings and functionality but this broadly reflects the "Rugby" implementation of c2008. AXLE COUNTER SPECIAL CONTROLS This CT concerns the reset-restore functionality of the various axle counter sections which are all listed as separate lines of entry. "Reset Requires": List all routes from controlled signals (including GPL and pre-set shunts) that read directly (i.e not foul, flank or overlap) over the section concerned List any auto signal that reads over the section concerned. In fringe areas also list the slot from the adjacent box that proves normal any relevant signals reading over the section "or EPR applied": List the EPR section number. auto signals / slots not proved "or STR applied": List the EPR section number. auto signals not proved "Special controls": Add any cross references; for example "sequential track section proving controls required" at interlocking boundaries for example. ---------------------------------------------------------------------------------------------------------------------------------------- ASPECT RESTRICTION CONTROLS This CT defines the logic applicable for the Aspect Restriction functionality (i.e. when it is / not enforced following a reset) "ARFR segment": List for each section the common segments, then reverse segments, then normal segments as separate rows of entry. "Applied- to signal /route": List the auto signal and controlled signal routes that are held to red by the particular ARFR segment [note this can be checked by cross-reference to Signal Specials sheet]. "Applied- except when points set and detected": List point conditions when ARFR is not applied. "Applied- except when EPR applied": List the EPR for the section (i.e the track section name). "Applied- except when STRapplied": List the STR for the section (i.e the track section name). "Removal requires- track section occupied" List the track(s) whose occupancy removes the ARFR; generally the track section for the ARFR segment, but may also include foul TCs in some circumstances. "Removal requires- after route operated" List any routes that must also be set as well as track occcupancy in order to remove ARFR; only required where there are set back moves that could mean that sweep train may not traverse whole length of that track. "Removal requires- signal off" Similarly used where need to prove train has traversed entire length of track section, list those signals that must be off or ready to clear. "Points set" Similarly where necessary list point conditions necesssary for ARFR to be removed. "or EPR applied" List the EPR for the flank track as condition on previous column. ---------------------------------------------------------------------------------------------------------------------------------------- EPR / STR CONTROLS This CT defines the functionality applicable to the EPR / STR reminders (that themselves affect the imposition of Aspect Restriction). "Track section" The track section to which the other controls apply. List in alphabetical order as separate rows of entry. "Application requires- Track section clear" The track which must be clear in order to be able to apply EPR/STR (which will always be the same identity as the first column of course). "Application requires- Routes Normal" List all routes from controlled signals that read directly over the affected section. Also in fringe areas those slots which ensure that contolled signals / ato signals are replaced. "Application requires- EPR /STR not applied" List the same track section yet again (this is the cross proving that ensures that an EPR and STR cannot be simultaneously applied). "Removal requires- track section clear" List the same track section yet again. "Removal requires- routes normal" List the same routes as for the application. "Removal requires- special controls" List any other locking to prevent removal. -------------------------------------------------------------------------------------------------------------------------------------------- SPECIAL SIGNAL CONTROLS This CT is effectively an overflow from the normal route and aspect CTs- all the axle counter related controls which are additional to those that would be needed with track circuits are shown here on the appropriate line. "Signal / Route" List each signal number for auto signals and each route from each controlled signal in separate rows of entry. "Aspect Restriction not applied to Axle Counter sections / segments" List each axle counter section / segment in the line of route or foul thereof (i.e. not overlap nor flank). Note that it is necessary to aspect restrict a route if a foul section to it has been reset, since if it were actually occupied then there is a risk of the signalled train hitting the obstruction "STR not applied or effective for one train only" List the STR (if provided) for each axle counter section in line of route only- not foul, flank nor overlap. Note that the train being signalled will only be occupying (and hence potentially creating a miscount) on those sections in the route itself "EPR not applied" List the EPR for each axle counter section in line of route only- not foul, flank nor overlap. Note that EPRs will be applied for all the track sections within the limits of the possession and hence any section upset by a train movement will be able to be reset without aspect restriction afterwards As you can see these control tables are pretty repetitive- I think because it was felt that there needed to be a CT that exactly specified to ensure that the data is easily derived from them and to provide somewhere for the tester to tick. Don't tend to do this for interlocking more generally- I think details were included because the approach was "novel" and there wasn't the accumulated body of experience in the industry as there is for other locking. ============================================================================== Although it doesn't actually address the controls, the attached powerpoint that was used to introduce the concept of EPR and STR for initial application on the WCRM some years ago does give a good idea of the overall process.
PJW
|
|
« Next Oldest | Next Newest »
|
Users browsing this thread: 1 Guest(s)