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Post by jimbo on Aug 25, 2019 19:28:27 GMT
Separated my thought lost in the 'Managers Driving Trains During Strikes' thread:
A vague memory has surfaced of a proposed long-term system-wide strike around 1980. Signals dept had no experience of a long-term stoppage, and were worried that relays may stick so it was proposed that Area Managers would work the occasional empty train on all routes every day. But talks overcame the strike, so it never became reality.
Did the problem of sticking relays arise after 7/7 resulted in some long term closures?
Was this a valid concern?
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Colin
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Post by Colin on Aug 25, 2019 20:58:17 GMT
From my perspective as a driver there were no issues.
A bigger problem these days, AIUI, is that an area needs to be fully tested if it isn't used for a number of days (more than a weekend). It's the length of time required to do those tests that can delay the railway coming back into use.
This is what I was told in relation to the commissioning of CBTC on the Hammersmith to Latimer Road section. There is a concern that if say after a week and a half of CBTC, the decision was made to revert back to the legacy signalling system, it would take a considerable amount of time to fully test the legacy system before it can operate a public service.
This is why confidence needs to be high before switching to the new system, cos once you've run it for a week or so, you've gotta stick with it.
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Post by londonstuff on Aug 25, 2019 21:04:17 GMT
From my perspective as a driver there were no issues. A bigger problem these days, AIUI, is that an area needs to be fully tested if it isn't used for a number of days (more than a weekend). It's the length of time required to do those tests that can delay the railway coming back into use. This is what I was told in relation to the commissioning of CBTC on the Hammersmith to Latimer Road section. There is a concern that if say after a week and a half of CBTC, the decision was made to revert back to the legacy signalling system, it would take a considerable amount of time to fully test the legacy system before it can operate a public service. This is why confidence needs to be high before switching to the new system, cos once you've run it for a week or so, you've gotta stick with it. As I understand it, TBTC on the Jubilee was far from perfect but I gathered that the time that after testing and testing and testing (with there being so so many shutdowns) and it still not being right, they switched over anyway and more or less decided to fix anything that still wasn’t right while it was being used. I’m sure there was more than a wing and a prayer for that upgrade. |
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Colin
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Post by Colin on Aug 25, 2019 21:10:21 GMT
They're doing their best to avoid fixing things after go live on CBTC which is why we're seeing soo many false starts.
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Tom
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Post by Tom on Aug 26, 2019 10:44:54 GMT
The problem wasn't sticking relays per se, but more the risk that the running rails had become rusty and that track circuits would not operate correctly.
The requirement is that there must be train moves every:
72 hours, for passenger routes in open or cut and cover sections, or up to the first station within a tube section.
7 days for shunt moves (subject to the design of the signalling at each location), passenger moves in tube tunnels, and in depots.
If you can't achieve this, then specific controls have to be introduced when the service recommences - usually either a test of the signalling system and it being formally recommissioned into use (as happened after 7/7 and the Grenfell Tower fire), or running a test train to clean the rails and check the track circuits operate correctly (as is often done after long closures for engineering work - I've had to do it three or four times myself).
After 7/7, whilst I wasn't directly involved I do know some cable repairs were needed, and the formal recommissioning of each location was as much to ensure that all the damage had been correctly repaired and the signalling was fit for use as much as it was for the correct operation of track circuits.
Specifically with regard to 4LM, if reversion is needed then technically the risk for rusty rails doesn't apply, as trains have been moving over those sections keeping the railhead clean. However, there is still a possibility that ballast resistance conditions have changed and then the track circuits may need adjusting to get them back into specification. Reversion wouldn't be a simple case of putting it all back after the first three days, there would almost certainly be a need for either an early finish of the service, a late start up, or both, to achieve it all. (This is an area I can comment on with some certainty - I'm specifying the extent of re-testing!)
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Tom
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Post by Tom on Aug 26, 2019 10:49:28 GMT
As I understand it, TBTC on the Jubilee was far from perfect but I gathered that the time that after testing and testing and testing (with there being so so many shutdowns) and it still not being right, they switched over anyway and more or less decided to fix anything that still wasn’t right while it was being used. I’m sure there was more than a wing and a prayer for that upgrade. They're doing their best to avoid fixing things after go live on CBTC which is why we're seeing soo many false starts. Technically, you're both right. The number of false starts has been because of things that have been found during testing and required fixing before entering service. However not everything has been addressed. This has been accepted and a decision has been made to commission with a less than perfect system, which means that there are things which still need addressing in subsequent software drops. I accept we're drifting off topic a bit here, so I'll make this the last on the subject of reverting CTBC in this thread. |
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Deleted
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Post by Deleted on Aug 26, 2019 13:49:59 GMT
There has been issues with relays becoming mechanically stuck but the main risk after a closure or strikes when trains haven’t been running in conventional signalling is that the track relay fails to drop away when a train shunts the track.
Do you remember Upminster Depot after a derailment Tom? That’s my last dealings with rusty rails where the track circuit wouldn’t shunt correctly
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Post by jimbo on Aug 26, 2019 20:06:10 GMT
The problem wasn't sticking relays per se, but more the risk that the running rails had become rusty and that track circuits would not operate correctly. The requirement is that there must be train moves every: 72 hours, for passenger routes in open or cut and cover sections, or up to the first station within a tube section. 7 days for shunt moves (subject to the design of the signalling at each location), passenger moves in tube tunnels, and in depots. .... 72 hours would cover weekend closures. And I guess the timetable would include all passenger moves. From my days on LU long back, the booked rusty rail trains were few and far between. Do they now cover all possible shunt moves within a week? |
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Tom
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Post by Tom on Aug 27, 2019 3:47:45 GMT
Do you remember Upminster Depot after a derailment Tom? That’s my last dealings with rusty rails where the track circuit wouldn’t shunt correctly Don't remind me! |
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