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Post by Deleted on Jun 23, 2016 21:04:52 GMT
The Circle line is currently suspended "while we fix a signal failure caused by flooding at Farringdon" and it's affecting the H & C and the Met as well. I noticed a signal failure at Farringdon was causing problems hours ago, I assume this is the same one.
Anyone have any more information on precisely what happened? I assume it's related to the floods, but it seems Farringdon especially has had a bad failure?
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Post by superteacher on Jun 23, 2016 21:12:44 GMT
I think Farringdon is a serial offender for signal failures!
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Post by Deleted on Jun 24, 2016 6:00:52 GMT
The fault was down to the flooding but when they tried to boost up the track to compensate for the dampness they found a faulty capacitor
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class411
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Post by class411 on Jun 24, 2016 8:33:38 GMT
The fault was down to the flooding but when they tried to boost up the track to compensate for the dampness they found a faulty capacitor Could you explain "boost up the track", please? That's a little too technical for me. |
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Post by Harsig on Jun 24, 2016 11:56:28 GMT
The fault was down to the flooding but when they tried to boost up the track to compensate for the dampness they found a faulty capacitor Could you explain "boost up the track", please? That's a little too technical for me. Basically it means increasing the power in the track circuit. At all times a certain amount of current leaks from one rail to the other in a track circuit via the ballast, sleepers etc. The size of this partial short circuit is determined by the ballast resistance. Generally a track circuit is set up such that, despite this leakage sufficient power reaches the relay at the far end to operate it. When there is a sudden decrease in the ballast resistance, such as might be caused by heavy rain saturating the track bed, the size of the partial short circuit may increase to the point where insufficient power reaches the relay to operate it, causing the track circuit to fail. This is got round by increasing the power in the circuit and is known as boosting the track. When the ballast resistance increases again as the track dries out, the track must be de-boosted. Failure to do so introduces a risk that the track circuit may fail to detect the presence of a train as sufficient power may still reach the relay despite the short circuit applied by the train wheels. In practice such a short circuit can never be relied upon to have a zero resistance, so some current will always flow via alternative paths such as the relay coil. Certain sections of line are more prone to track circuits requiring regular adjustments, and this depends largely on the state of track drainage. Baker Street to Finchley Road is currently one of the worst sections of line in this regard, hence the current evening closures of this section. |
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class411
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Post by class411 on Jun 24, 2016 12:42:40 GMT
Could you explain "boost up the track", please? That's a little too technical for me. Basically it means increasing the power in the track circuit. At all times a certain amount of current leaks from one rail to the other in a track circuit via the ballast, sleepers etc. The size of this partial short circuit is determined by the ballast resistance. Generally a track circuit is set up such that, despite this leakage sufficient power reaches the relay at the far end to operate it. When there is a sudden decrease in the ballast resistance, such as might be caused by heavy rain saturating the track bed, the size of the partial short circuit may increase to the point where insufficient power reaches the relay to operate it, causing the track circuit to fail. This is got round by increasing the power in the circuit and is known as boosting the track. When the ballast resistance increases again as the track dries out, the track must be de-boosted. Failure to do so introduces a risk that the track circuit may fail to detect the presence of a train as sufficient power may still reach the relay despite the short circuit applied by the train wheels. In practice such a short circuit can never be relied upon to have a zero resistance, so some current will always flow via alternative paths such as the relay coil. Certain sections of line are more prone to track circuits requiring regular adjustments, and this depends largely on the state of track drainage. Baker Street to Finchley Road is currently one of the worst sections of line in this regard, hence the current evening closures of this section. Thanks; excellent explanation. |
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Ben
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Post by Ben on Jun 24, 2016 14:52:19 GMT
Baker Street to Finchley Road seems to have been a constant cause of headache for decades!!
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metman
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Post by metman on Jun 24, 2016 18:34:57 GMT
Great explanation I always wondered how flooding would affect a track circuit.
I had a terrible time getting home last night with only a Baker St - Harrow and Wembley - Ricky service running!
At about 23:50 the harrow terminator pulled into Plat 3 and the Ricky local on 4 and everyone looked around in confusion. Total chaos! The guys thought that perhaps both trains were going to Ricky space permitting. Goodness knows what it was like at the start of traffic this morning!
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Post by Deleted on Jun 24, 2016 18:41:23 GMT
At about 23:50 the harrow terminator pulled into Plat 3 and the Ricky local on 4 and everyone looked around in confusion. Total chaos! The guys thought that perhaps both trains were going to Ricky space permitting. Goodness knows what it was like at the start of traffic this morning! Yeah, I didn't think it was possible to reverse from HOTH platform 3? |
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Post by Deleted on Jun 24, 2016 19:16:59 GMT
Could you explain "boost up the track", please? That's a little too technical for me. Basically it means increasing the power in the track circuit. At all times a certain amount of current leaks from one rail to the other in a track circuit via the ballast, sleepers etc. The size of this partial short circuit is determined by the ballast resistance. Generally a track circuit is set up such that, despite this leakage sufficient power reaches the relay at the far end to operate it. When there is a sudden decrease in the ballast resistance, such as might be caused by heavy rain saturating the track bed, the size of the partial short circuit may increase to the point where insufficient power reaches the relay to operate it, causing the track circuit to fail. This is got round by increasing the power in the circuit and is known as boosting the track. When the ballast resistance increases again as the track dries out, the track must be de-boosted. Failure to do so introduces a risk that the track circuit may fail to detect the presence of a train as sufficient power may still reach the relay despite the short circuit applied by the train wheels. In practice such a short circuit can never be relied upon to have a zero resistance, so some current will always flow via alternative paths such as the relay coil. Certain sections of line are more prone to track circuits requiring regular adjustments, and this depends largely on the state of track drainage. Baker Street to Finchley Road is currently one of the worst sections of line in this regard, hence the current evening closures of this section. Couldn't of put it better then myself |
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Post by crusty54 on Jun 24, 2016 19:56:37 GMT
The track at Farringdon has always bounced up and down with each train. The early evening closures between Baker Street and Finchley Road are to sort out severe drainage problems.
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Post by philthetube on Jun 24, 2016 23:11:37 GMT
At about 23:50 the harrow terminator pulled into Plat 3 and the Ricky local on 4 and everyone looked around in confusion. Total chaos! The guys thought that perhaps both trains were going to Ricky space permitting. Goodness knows what it was like at the start of traffic this morning! Yeah, I didn't think it was possible to reverse from HOTH platform 3? It would probably be a rusty rail move reversing via Rayners Lane Westbound Platform. |
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Post by marri260 on Jun 26, 2016 1:03:12 GMT
Most trains through Harrow Platform 3 after the tree came down at Northwood were reversing at Rayners off of Platform 1 yes. They came to us in passenger service though.
Left Harrow Platform 4 free for turning trains through the siding, as there are no shunt or wrong road moves available from Platform 3 as has been stated.
Believe the flooding between Ruislip and Ickenham caused no less than 6 track circuit failures.
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metman
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Post by metman on Jun 29, 2016 12:34:01 GMT
How did the wrong road reversing at rayners affect the Piccadilly line? Were there a few south harrow reversals?
There is usually a rusty rail move each evening to rayners which I think is a semi- fast harrow terminator.
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Post by marri260 on Jun 29, 2016 19:58:21 GMT
To be honest I don't know, my colleague was dealing with the platforms whilst I dealt with the gate line...
I imagine that given the situation, all Uxbridge trains would have turned at South Harrow, and the Rayners run through as normal.
Normally T421 (off the top of my head) does the rusty rail move off of Platform 1 at about 0035 yes. Believe it comes empty off of Harrow Platform 3.
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