Heat related issues (25 July 2019 and subsequent days)

[Bald Rick]

Just to explain to people why these restrictions are in place:

Metal rails expand when they get hot. That's physics. If you welded them together at 10C and the temperature jumps to 30C, then the expansion will result in the rails wiggling as there's no room for them to expand, so they end up getting squished and they can buckle.

Engineers account for this by essentially stretching them when they're welded together. That way the heat will cause the rails to come back into their pre-stretched state instead of having them wiggle. If it's hotter than the pre-stretching compensated for then they'll still expand to the point of getting squished, alas the train can't go at full speed because it's dangerous to do so along rails that aren't straight.

As you might guess, the process of pre-stretching them costs money, and the price increases the more they're stretched. Someone somewhere crunched the numbers on what temperature it's worth spending money on dealing with (also accounting for winter lows) and that's how we have what we have.

Countries that have hotter summers will have also done these calculations and come up with a higher number, which is why you hear cries of "But the trains are running fine in Mexico and it's 40C!!!!", it's because it's common enough to spend money coping with it there but not here.

So yes it's annoying, but maybe knowing the reason will help a bit.

Just to pick up on the second half of this post. It doesn’t cost more money to ‘stretch’ (stress) the rails more.

When installing continuously welded rail, you have to pick a temperature at which there is no stress in the rails, and in this country we set that temperature at 27C - it is known as the Stress Free Temperature, or SFT. We could set it higher, but then that runs an increased risk of broken rails in winter - where rail temperatures can easily be below -10C.

Another point - rail temperature does not necessarily equal air temperature. The former is a function of air temperature, cloud cover, exposure of the rails to direct sun, and the angle of the sun (which is higher, and therefore more powerful, in the weeks around the summer solstice). It’s quite conceivable that we will get rail temperatures of nearly 60C tomorrow, and that will be close to route / region wide blanket speed restrictions. This is because it is impractical to impose potentially hundreds of emergency speed restrictions.

How they cope in other countries is to have a higher SFT. In the very few parts of the world with wider temperature ranges than the U.K. (eg the Russian steppes), they will restress the rails for a different SFT each spring and autumn. Or put up with buckled rails.

 

[ag51ruk]

The amount of people getting on non air conditioned trains, or indeed buses, feeling the heat, and then assuming the heating is on, and moaning on Twitter about it.

They’ve obviously never stepped foot in a greenhouse and realised the heating isn’t on in there either.

It may be - one of my local bus companies confirmed (in writing) that on some of their older buses the heating needed to be on in hot weather to prevent the engine from overheating.

 

[westv]

It may be - one of my local bus companies confirmed (in writing) that on some of their older buses the heating needed to be on in hot weather to prevent the engine from overheating.

That is absolutely crazy!

 

[43055]

East Midlands Trains advertising not to travel tomorrow on the mainline to London with a revised timetable all day. The PDF timetable gives an extra hour to end to end journey times from around midday onwards.

Services that are running (as a guide as it is different at peak times):
Kettering to Corby as a shuttle
Sheffield semi fasts xx:31 from London, xx:00 from Sheffield
Nottingham slows xx:05 from London, xx:12 from Nottingham

 

[Peter Mugridge]

There was one or 2 clips on YouTube of a track buckling. Is that actually real or can tracks buckle that at the same speed as when you blink?

In the video, it sounds similar to a gate being opened.

Yes, it can. Think how much pressure there is in the rail; if just one thing holding it tightly in place lets go, that pressure is going to release itself very quickly indeed.

 

[scotraildriver]

"How come other countries cope" is a moan I hear relentlessly from passengers. Well, having travelled around Paris 3 weeks ago in hot weather I think we actually do rather well. Carnage on the RER - power issues, short formations, no air con, major engineering works. ....... TGV services in meltdown and a typical French shrug of the shoulders when asking for information. Not to mention horrific overcrowding on a scale rarely seen here. We're not that bad!

 

[CheshireCrusty]

When installing continuously welded rail, you have to pick a temperature at which there is no stress in the rails, and in this country we set that temperature at 27C - it is known as the Stress Free Temperature, or SFT. We could set it higher, but then that runs an increased risk of broken rails in winter - where rail temperatures can easily be below -10C.

I vaguely remember some 50+ years ago, an acquaintance was working on a new freight line bringing ore to Port Headland in Western Australia. He told me that they had installed a 300 mile section of welded track which extended and contracted less than 5cm (2inches) over its whole length with the range of temperatures experienced in the desert conditions there. Don't know whether this was a tall story or not - or whether the expansion is the same irrespective of the length of track.

 

[TheEdge]

How they cope in other countries is to have a higher SFT. In the very few parts of the world with wider temperature ranges than the U.K. (eg the Russian steppes), they will restress the rails for a different SFT each spring and autumn. Or put up with buckled rails.

How do they do that to rail in situ? Or do they relay with appropriately stressed rails?

 

[westv]

With reduced speeds from Kings X to Peterborough does anybody want to estimate how much longer it will take for, say, this evening's 17:33 to Harrogate to get to Doncaster?

 

[edwin_m]

I vaguely remember some 50+ years ago, an acquaintance was working on a new freight line bringing ore to Port Headland in Western Australia. He told me that they had installed a 300 mile section of welded track which extended and contracted less than 5cm (2inches) over its whole length with the range of temperatures experienced in the desert conditions there. Don't know whether this was a tall story or not - or whether the expansion is the same irrespective of the length of track.

Probably because modern track isn't allowed to expand and contract - it is held in place by the ballast sleepers and fastenings. At higher temperatures than the SFT (see above) it has compression forces because the rail is trying to expand, hence it will buckle if the temperature gets too high or there isn't enough ballast to stop the sleepers moving. At lower temperatures it has tension forces because the rail is trying to contract, so it may break if the temperature gets too low or there is a flaw in the steel. The very ends of a welded section may be free to move and that might explain the 5cm.

How do they do that to rail in situ? Or do they relay with appropriately stressed rails?

Do some calculations based on the current temperature and the SFT, then cut a piece of the correct length out of the rail, pull the ends together with powerful jacks and weld it back together. This is done after CWR is laid (sometimes not immeditely after, in which case there may be more of a speed restriction if it gets warm before it can be done). To lower the SFT of the rail you would have to cut it and insert a new section - you might have to remove the fastenings to allow the rail to contract. I don't think you can do either when the temperature is above the desired SFT, unless you find some way of cooling the rail.

 

[43055]

With reduced speeds from Kings X to Peterborough does anybody want to estimate how much longer it will take for, say, this evening's 17:33 to Harrogate to get to Doncaster?

I don't know for the East Coast but East Midlands services have been timetabled for a extra hour between Leicester and London but looking at Real Time Trains it looks like LNER have ammend the times to show the longer journey. This is the 1733:
http://www.realtimetrains.co.uk/train/Y31108/2019/07/25/advanced

 

[westv]

I don't know for the East Coast but East Midlands services have been timetabled for a extra hour between Leicester and London but looking at Real Time Trains it looks like LNER have ammend the times to show the longer journey. This is the 1733:
http://www.realtimetrains.co.uk/train/Y31108/2019/07/25/advanced

Many thanks. So it looks like I should get there in time to get the 20:00 to Hull.

 

[al78]

The trains do a remarkable job of dealing with unseasonable weather. Problem these days is people expect perfection.

Nol they don't, the robustness of the UK rail network is poor in my experience. It goes tits up in hot weather, tits up in cold weather, tits up in wet weather, tits up if the sun shines a bit too bright, tits up when it snows. I'm just glad I have a home and a job close to each other so that I don't rely on it.

 

[Peter C]

Nol they don't, the robustness of the UK rail network is poor in my experience. It goes tits up in hot weather, tits up in cold weather, tits up in wet weather, tits up if the sun shines a bit too bright, tits up when it snows. I'm just glad I have a home and a job close to each other so that I don't rely on it.

The UK rail system is very good when you consider that:

-A lot of the stations are over 200 years old
-A lot of the trains are 30 years old
-The system is the oldest in the world and when it was designed it had no other system to learn from
-The system is so big that, yes, you may want the system improved, it is not possible to just "improve" everything overnight.

-Peter

 

[modernrail]

Nol they don't, the robustness of the UK rail network is poor in my experience. It goes tits up in hot weather, tits up in cold weather, tits up in wet weather, tits up if the sun shines a bit too bright, tits up when it snows. I'm just glad I have a home and a job close to each other so that I don't rely on it.

From an engineering perspective, is it possible to stretch the rail to deal with the maximum likely spread of air temperatures in the UK, lets say -20 to +45 (So max experienced to date plus some additional headroom bearing in mind we are on notice we could have yet bigger swings and higher/lower max)? I understand that this would come with a cost penalty but is it actually possible from an engineering perspective?

Do we have a genuinley wide spread of temperatures compared to other places? I would have thought the NE corridor from Washington to Boston has a much wider and consistent spread. What happens with the rail there I wonder? I pick this example because the Americans are notorious for underspending on infrastructure resilience..maybe the service is just subject to big delays in hot/cold weather?

The other point I have always wondered about is what our OHL equipment and lineside electrical infrastructure is built to take. I presume there is a hotch potch depending when it was put in but is there a NR standard min/max for new installations or is it worked out on a per installation basis?

 

[Peter C]

From an engineering perspective, is it possible to stretch the rail to deal with the maximum likely spread of air temperatures in the UK, lets say -20 to +45 (So max experienced to date plus some additional headroom bearing in mind we are on notice we could have yet bigger swings and higher/lower max)?
The other point I have always wondered about is what our OHL equipment and lineside electrical infrastructure is built to take. I presume there is a hotch potch depending when it was put in but is there a NR standard min/max for new installations or is it worked out on a per installation basis?

Personally, I don't know a lot about this sort of thing but I would say that yes, whilst it is physically possible to change the rails to deal with higher temperatures, it wouldn't happen on a major scale purely because the railways are so busy that even closing a small branch for one or two days could be a mess.
Also, I would say that the OHLE and lineside equipment is probably designed for "standard" UK temperatures, which are normally 10 - 15 degrees I would say. However, NR are probably installing new equipment with better resistances to heat. Just my thoughts.

-Peter

 

[ashkeba]

Do we have a genuinley wide spread of temperatures compared to other places? I would have thought the NE corridor from Washington to Boston has a much wider and consistent spread. What happens with the rail there I wonder? I pick this example because the Americans are notorious for underspending on infrastructure resilience..maybe the service is just subject to big delays in hot/cold weather?

I was there in extreme heat. Firstly, their services tend to run slower than ours anyway, which I guess reduces risk. Secondly, some of their scheduled station dwells make XC seem positively rushed. And finally, if anything went wrong, it seemed like they didn't hesitate to cancel two DAYS of long distance services: the first due to the problem, the second due to repositioning stock.

 

[Bald Rick]

From an engineering perspective, is it possible to stretch the rail to deal with the maximum likely spread of air temperatures in the UK, lets say -20 to +45 (So max experienced to date plus some additional headroom bearing in mind we are on notice we could have yet bigger swings and higher/lower max)? I understand that this would come with a cost penalty but is it actually possible from an engineering perspective?

Do we have a genuinley wide spread of temperatures compared to other places? I would have thought the NE corridor from Washington to Boston has a much wider and consistent spread. What happens with the rail there I wonder? I pick this example because the Americans are notorious for underspending on infrastructure resilience..maybe the service is just subject to big delays in hot/cold weather?

The other point I have always wondered about is what our OHL equipment and lineside electrical infrastructure is built to take. I presume there is a hotch potch depending when it was put in but is there a NR standard min/max for new installations or is it worked out on a per installation basis?

To answer your 3 points:

1) no it isn’t possible to stress the rails to cover a wider range of temperatures. You can set to one stress free temperature (SFT) and the range around that is fixed. At a certain figure above that temperature (here, it is 32C above SFT IIRC) you risk track buckles. At a slightly less certain figure below the SFT (around 40C , but it varies) you risk a higher number of broken rails. It’s the laws of physics, and they apply universally. It is not a cost issue.

2) the NE corridor has a similar spread to us; perhaps with a slightly higher top end. I think their SFT is set 1 or 2C higher, and they run the risk of more broken rails in winter

3) all OLE installed since the 60s can take more than the temperature range that occurs in the U.K., as long as it is maintained to its original state. The only troublesome OLE is fixed tension equipment, but most of that has now gone. The last time it was this hit, we had OLE lying on top of trains on the GEML as it had sagged so much.


A final point. With the possible exception of today, all speed restrictions on the track caused by the heat are because the SFT is lower than the normal 27C on a particular section of track. SFT can be lower because of recent work that has disturbed the integrity of the ballast (simply digging out a wet bed is enough), or because newly installed rail has yet to be stressed. Given that this hot spell has been forecast for about a week, much of this work would have been stopped, however work done some weeks ago can still cause a reduction in SFT.

I did a lengthy post on the subject a year or two ago, I will see if I can find it.

Edit: this might help

https://www.railforums.co.uk/threads/if-tracks-buckle.166350/#post-3524837

 

[westv]

Seeing as this thread has developed into the technicalities of rail heating is it worth creating another thread for anybody else requiring travel assistance on the ECML today?

 

[TheManOnThe172]

Any ideas where I should look for confirmation that XC Advance tickets for cancelled trains on Thursday will be accepted for travel on Friday?

The National Rail page gives details of savaged services for many TOCs, but only for Hull Trains is a ticket easement mentioned.

 

[Silver Cobra]

With reduced speeds from Kings X to Peterborough does anybody want to estimate how much longer it will take for, say, this evening's 17:33 to Harrogate to get to Doncaster?

LNER's travel alerts page suggests that all services from 1130 onwards will be delayed by around 35 minutes travelling between Kings Cross and Peterborough.

 

[221129]

Any ideas where I should look for confirmation that XC Advance tickets for cancelled trains on Thursday will be accepted for travel on Friday?

The National Rail page gives details of savaged services for many TOCs, but only for Hull Trains is a ticket easement mentioned.

As far as I can see there is no such easement for XC.

 

[CheshireCrusty]

Probably because modern track isn't allowed to expand and contract - it is held in place by the ballast sleepers and fastenings.

Thank you very much for your informative reply.

I guess in the 1960's there were few sections of welded track in the UK!

 

[JB_B]

The UK rail system is very good when you consider that:

-A lot of the stations are over 200 years old
...
-Peter

Which stations are you thinking of?

 

[Peter C]

Which stations are you thinking of?

OK. Maybe not over 200 years old, but Paddington, St. Pancras, King's Cross, etc. are all approaching 200 years old. I should have been more careful with what I said and I apologise for any annoyance caused.

-Peter

 

[TheManOnThe172]

As far as I can see there is no such easement for XC.

I tweeted them, and to their credit they replied within 30 minutes to say "yes you can use today`s Advance ticket for travel tomorrow instead."

But it shouldn't take individuals asking questions to get this offered - it should be on National Rail and XC websites. Poor show.

 

[700007]

TfL Rail all trains today have been booked to be 345s as they have air conditioning, so I have been told. 315s given the day off!

 

[DarloRich]

Is the issue today that speed restrictions are being imposed widely because of the high expected temperature rather than because of any recent work? It is said today may be the hottest on record!

 

[AM9]

That is absolutely crazy!

Much better to let the engine overheat, take the bus out of service and then cancel the service for the rest of the day. Problem fixed!

 

[westv]

Much better to let the engine overheat, take the bus out of service and then cancel the service for the rest of the day. Problem fixed!

Isn't that just swapping one bit of craziness for another?