Speed Restrictions on FCC This Evening

The Box Photter · 12 Jun 2014

Most northbound FCC trains from 3rd rail land were running 5-10 mins late tonight. Supposed cause (according to FCC Twitter feed) was NR speed restrictions due to hot weather.

I know its been a over 20 degrees celsius today, but isn't that a bit of an overreaction? Or have the risk-averse taken control at Network Rail. If the rails are capable of buckling at 22 degrees celsius, then we'd better look forward to longer journeys until the end of September.

Can anyone in the know shed light (but not any more heat) on the topic?

RailUK Forums

hassaanhc · 12 Jun 2014

Seems to be an issue in the Sutton area. Temperatures reached 26 today, and rail temperatures can easily be 15 degrees higher.
In depth info on the Network Rail website http://www.networkrail.co.uk/timetables-and-travel/delays-explained/buckled-rail/?cd=1
Introduction:

On warm days, rails in direct sunshine can be as much as 20 degrees centigrade above air temperature. As rails are made out of steel, they expand as they heat up and are subject to strong compression. This expansion has to be managed to reduce the risk of track buckling.

If the track does buckle, the line must be closed and the track repaired before services can resume, causing considerable disruption. Usually, these repairs can't be done until the temperature of the rails has dropped.

If a section of track is judged to be at risk, we introduce local speed restrictions - slower trains exert lower forces on the track and reduce the chance of buckling.

The Box Photter · 12 Jun 2014

Thanks for the info.

I'd rather be on a slower slightly delayed train than a derailed one!

hassaanhc · 12 Jun 2014

That is why you find rails around crossovers and other problem areas are painted white, as that colour reflects the most heat. It seems most trains would have been fine, something must have happened in that area for the speed limit to be required, possibly something unrelated as well!

user15681 · 12 Jun 2014

There are speed restrictions at Herne Hill, so if there are around Sutton too then that's two locations.

455driver · 12 Jun 2014

Possibly because the rail stressing is outside spec.

AM9 · 12 Jun 2014

455driver said:
Possibly because the rail stressing is outside spec.

Does the stress figure get altered for high current drain situations, e.g. 6-8000A draw?

455driver · 12 Jun 2014

AM9 said:
Does the stress figure get altered for high current drain situations, e.g. 6-8000A draw?

Haven't a clue, I do know that older/worn rails are more susceptible to these speed restrictions.

tsr · 12 Jun 2014

There were also restrictions near St Albans, and I believe maybe around Flitwick and Preston Park. There was a fairly harsh restriction at Stoats Nest Junction the other day, but that didn't seem to be causing major issues tonight, so I guess any limits there may have involved teething problems after the Christmas renewals, which perhaps have now been sorted out.

user15681 · 12 Jun 2014

tsr said:
There were also restrictions near St Albans, and I believe maybe around Flitwick and Preston Park. There was a fairly harsh restriction at Stoats Nest Junction the other day, but that didn't seem to be causing major issues tonight, so I guess any limits there may have involved teething problems after the Christmas renewals, which perhaps have now been sorted out.

I'm not 100% as I haven't been around the Herne Hill area today, but I'm fairly certain this speed restriction was in the same location as a TSR at the start of the year, at the country end of P3 and 4 where the Down Holborn diverges.

The Box Photter · 12 Jun 2014

I thought that when track is installed it is stretched to "distress" it and thus reduce the capacity for buckling.

Is the juice rail also stretched in the same way? I can see that if it isn't it would be the third rail that would be the issue south of the river.

Laryk · 12 Jun 2014

The Box Photter said:
I thought that when track is installed it is stretched to "distress" it and thus reduce the capacity for buckling.

Not necessarily de-stress, but the rail is tensioned and secured at that tension. As the temp increases the rail remains in tension, reducing until the temperature matches that of which it was stressed for. Past this point the rail will go into compression, and will be at risk of buckling. Rail is typically stressed for an air temperature of 28c. However, most switches and crossings cannot be stressed, so are much more susceptible to buckling than plain line.

The Box Photter said:
Is the juice rail also stretched in the same way? I can see that if it isn't it would be the third rail that would be the issue south of the river.

The Conductor rail isn't stressed, as it is not fixed in place like the running rails. It is allowed to expand, and as lengths don't tend to be longer than 300m the expansion is not as great as a length of CWR (continuously welded rail)

Note that the insulators that hold the rail only prevent sideways movement

infobleep · 12 Jun 2014

Have these issues always been a problem for the railways going back turns of years?

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carriageline · 12 Jun 2014

For everyone concerned, watch out for videos at platforms! There will be a short video explaining why heat affects rail and how, and why speed restrictions are imposed, identical to the one they used for leaves on the line!

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user15681 · 12 Jun 2014

infobleep said:
Have these issues always been a problem for the railways going back turns of years?

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I can't speak for many many years ago, but I remember being told a story about a buckle due to hot weather in 1990 outside Faversham. The train went over the buckle at 20mph and, having seen pictures, I'm amazed it stayed on the track and even continued in service. I'll try find pictures.

Said picture...

Kentrail.org.uk

The Box Photter · 12 Jun 2014

Perhaps the new "standard" should be to stress the running rails at 32 or 35 degrees, given the likelihood that summers will become warmer in the future. Would doing that increase the risk that rails would break more easily in extreme cold? I'm no engineer but I'm genuinely interested.

Looking at that picture, I suspect that no trains would be run over a similar piece of track today. Given that switches & crossings are inherently more likely derailment points, I can see why even a small deformation could cause problems.

Is there a case for looking at alternative materials for switches and crossings such as carbon ceramic, which might have more tolerance for extremes of temperature?

hassaanhc · 12 Jun 2014

Temple said:
There are speed restrictions at Herne Hill, so if there are around Sutton too then that's two locations.

Their Journeycheck page was saying "...has been delayed at Sutton (Surrey)..." but you're probably right, as any delays between stations have the names of the next station attributed to it (e.g. if diverted they say they will be delayed at the station after returning back to normal route). I'm not sure if they have stops around the Herne Hill area.

LBSCR Times · 13 Jun 2014

The speed restriction at Herne Hill had been reduced to 5mph.
Everything coming from either Blackfriars or Victoria had to be stopped and cautioned over the affected section.
Therefore trains from Sutton were late due to late arrival.

Coupled with the incident at Denmark Hill, with all the South Eastern services that normally run that way having been diverted via Herne Hill too!

Bald Rick · 13 Jun 2014

The Herne Hill restriction is due to a serious rail defect. 5mph.

As for the various heat speeds and the reasons why they apply, this was discussed in another thread recently, I'll find the link

Needless to say, rails are normally stressed to be stress free at a rail temperature of 27c. But rails on good condition plain track can be another 32C warmer than this before there is a risk of buckling. Where heat speed restrictions are imposed is because the stress free temperature is lower than 27C, usually because it has recently been worked on.

Link to other thread - oddly in rolling stock section

http://www.railforums.co.uk/showthread.php?t=101651&page=3

SPADTrap · 13 Jun 2014

The Box Photter said:
Most northbound FCC trains from 3rd rail land were running 5-10 mins late tonight. Supposed cause (according to FCC Twitter feed) was NR speed restrictions due to hot weather.

I know its been a over 20 degrees celsius today, but isn't that a bit of an overreaction? Or have the risk-averse taken control at Network Rail. If the rails are capable of buckling at 22 degrees celsius, then we'd better look forward to longer journeys until the end of September.

Can anyone in the know shed light (but not any more heat) on the topic?

There was a test train around which certainly wasn't hanging around, could have found some defects as NR appeared not long after it passed south in the St Albans/Harpo area.

infobleep · 14 Jun 2014

The 12.41 Gatwick Airport to Brighton has been delayed by 12 minutes due to emergency speed restrictions in the St Albans area. However the 12.57 is on time. Does that mean the emergency speed restriction was lifted?

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infobleep · 14 Jun 2014

Actually I wonder if all trains have been delayed by the emergency speed restrictions but other trains had the ability to make up the time, where as this train is timed so closely to other trains that it then kept getting delayed by trains in front, which were running on time

Interestingly the train lost even more time between Haywards Heath and Brighton. I expected it to make up time. Perhaps there are heat problems there too. There was a Hove train in front but I'd have expected that to be out of our way fairly quickly as we stop at every station and that one doesn't.

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LBSCR Times · 14 Jun 2014

infobleep said:
Interestingly the train lost even more time between Haywards Heath and Brighton. I expected it to make up time. Perhaps there are heat problems there too. There was a Hove train in front but I'd have expected that to be out of our way fairly quickly as we stop at every station and that one doesn't.

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Held up for an Up Eastbourne train to cross over in front at Keymer Jct....

One of the wonders of travelling with FCC that Govia will find out about.
If they are late from the Midland route, then they will get regulated for on-time South Eastern and Southern trains, but not always, just to be consistent!

infobleep · 14 Jun 2014

I was on a late running Brighton fast train once at Haywards Heath. I think possibly a Southern service. I expected it to leave first but no, they let the stopping FCC service go in front. Both were at the station around the same time.

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cambsy · 20 Jun 2014

At what temperature does hot weather start to affect train running, by NR imposing speed restrictions? What temperature are the track designed to take before buckling?

Speed Restrictions on FCC This Evening

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