Trains running at 'reduced temperatures'

[leytongabriel]

The BBC news site reported today that trains in the West Midlands will run at reduced temperatures. Interesting! Any other examples to hand ?

Image source, West Midlands Railway
Image caption:-

Trains will run at reduced temperatures in the hot weather to try and prevent rails from buckling

UK heatwave: Hot tracks blamed for West Midlands rail disruption

Services between Stratford-Upon-Avon and Kidderminster are affected amid plans to reduce buckling risk.

www.bbc.co.uk

 

[Sonik]

Trains will run at reduced temperatures in the hot weather to try and prevent rails from buckling

LOL, how does that work?

 

[Urban Gateline]

LOL, how does that work?

Probably a typo, I'm sure they meant reduced speed

 

[PlatformEdgeVT]

I'm sure they meant reduced speed

Presumably, Lower Speed=Lower Engine Usage=Less Heat from Combustion

 

[swt_passenger]

Presumably, Lower Speed=Lower Engine Usage=Less Heat from Combustion

Lower speed as a precaution in case of any heat related track problems. Nothing to do with the engines, the same temporary speed limitations would apply to an EMU.

 

[geoffk]

I'm considering postponing my three days out with a Devon and Cornwall Rover ticket next week as I can see what might happen - very hot weather, speed restrictions, trains running late, missed connections. I've not yet bought my ticket and have until close on Friday to cancel my overnight stay!

 

[E27007]

Trains will run at reduced temperatures in the hot weather to try and prevent rails from buckling

In the statement above for temperatures, substitute speed.

I think the BBC is referring to a Blanket Speed Restriction imposed by P-Way for safety reasons, they are imposed in extremes of weather, Heat, Cold, High Winds, Rain (risk of floods). there may be a rolling stock issue, overheating of traction equipment, but I doubt it. We need to see the Late Notices or the Weekly Operating Notices Publications to unravel this one.

 

[swt_passenger]

I think the BBC is referring to a Blanket Speed Restriction imposed by P-Way for safety reasons, they are imposed in extremes of weather, Heat, Cold, High Winds, Rain (risk of floods). it may be a rolling stock issue, overheating of traction equipment, but I doubt it. We need to see the Late Notices or the Weekly Operating Notices Publications to unravel this one.

The BBC do refer to it being a track related speed restriction within the article text, it’s only their photo caption that’s wrong.

 

[Mikw]

Yeah, it's just what usually happens in hot weather, isn't it? Going slower because of the risk of track deformations.

 

[43301]

No doubt the interiors of 158s won't be at 'reduced temperatures'! I can confidently predict that up and down the land, the aircon in 158s will be failing, as normal when the weather gets a bit warm!

 

[dk1]

No doubt the interiors of 158s won't be at 'reduced temperatures'! I can confidently predict that up and down the land, the aircon in 158s will be failing, as normal when the weather gets a bit warm!

Hoppers open!!

== Doublepost prevention - post automatically merged: 12 Jul 2022 ==

I'm considering postponing my three days out with a Devon and Cornwall Rover ticket next week as I can see what might happen - very hot weather, speed restrictions, trains running late, missed connections. I've not yet bought my ticket and have until close on Friday to cancel my overnight stay!

RR on the Newquay branch too. It could be fun with all the out of course running but get what you mean.

 

[Snow1964]

Surely the photo caption is wrong way round

Trains will run at reduced temperatures in the hot weather to try and prevent rails from buckling

Isn’t it the passage of trains disturbs the air around the rails, thus bringing in cooler ambient air (rather than air heated by the hot rails), so helps cool the rails.

Thus really want to run trains faster (and ideally less streamlined ones like freight trains) to prevent buckling rather than fewer trains, or slower trains. Reducing the train speeds increases likelihood of rails staying hot.

UK heatwave: Hot tracks blamed for West Midlands rail disruption

Services between Stratford-Upon-Avon and Kidderminster are affected amid plans to reduce buckling risk.

www.bbc.co.uk

 

[railfan99]

What temperature is considered 'hot weather' when speed restrictions come into force?

 

[dk1]

What temperature is considered 'hot weather' when speed restrictions come into force?

Usually late 20s in my experience.

 

[Snow1964]

Usually late 20s in my experience.

That seems a bit low, in South East would get that on 20-40 days a year (it is in 80s in Fahrenheit), not exceptional

Surely restrictions should only be at unusual levels, sort of thing that only occurs on say 4 days or less per year, not routine every summer.

 

[Alfonso]

I'm considering postponing my three days out with a Devon and Cornwall Rover ticket next week as I can see what might happen - very hot weather, speed restrictions, trains running late, missed connections. I've not yet bought my ticket and have until close on Friday to cancel my overnight stay!

While all of that makes sense, it may affect Devon and Cornwall less than other places as speeds are already pretty low to start with

 

[dk1]

That seems a bit low, in South East would get that on 20-40 days a year (it is in 80s in Fahrenheit), not exceptional

Surely restrictions should only be at unusual levels, sort of thing that only occurs on say 4 days or less per year, not routine every summer.

Was always the way here in OHL country but more so these days over what appears newer track.

 

[StKeverne1497]

Genuine question - how much was track buckling a problem in the days before continuously-welded track? I presume even welded track isn't really "continuous" and must have some expansion joints somewhere so if (as some predict) we are going to see more, hotter, summer days as global temperatures rise, is there a case for reducing the distances between these joints as track is relaid?

 

[stuartl]

Genuine question - how much was track buckling a problem in the days before continuously-welded track? I presume even welded track isn't really "continuous" and must have some expansion joints somewhere so if (as some predict) we are going to see more, hotter, summer days as global temperatures rise, is there a case for reducing the distances between these joints as track is relaid?

I think that it is pre-stressed when it is laid i.e. 'stretched' so that it can accomodate temprature changes without problem. There is though a limit to the temperature range acording to how much it is pre-stressed. I'm sure someone will know the figures.

 

[swt_passenger]

I think that it is pre-stressed when it is laid i.e. 'stretched' so that it can accomodate temprature changes without problem. There is though a limit to the temperature range acording to how much it is pre-stressed. I'm sure someone will know the figures.

The rails are stretched after installation to be “stress free at 27° C”. Above that temperature the rails are going into compression. Rail temperature can get up to 20° above ambient or more.

Network Rail have issued a statement today:

Hot weather can cause a great deal of disruption to the railway so Britain’s rails are pre-stressed to help them resist high temperatures. Our rails have a stress-free temperature of 27 degrees – the UK mean summer rail temperature. Other countries choose different temperatures depending on their climate.

When the air temperature reaches 30 degrees, the temperature on the rail can actually be up to 20 degrees higher. More than three-quarters of track on the network today is modern on concrete sleepers. The movement of trains also generates forces in the track. The higher the speed, the greater the force of a train.

When heat expansion forces are high, trains deliberately slow down to reduce the additional forces they apply to the railway. The need to prevent problems also means there will be fewer trains, but this is better than causing a bigger problem and being unable to run any services.

Why rails buckle in Britain - Network Rail

Why don’t rails get hot in Europe? The truth is they do.

www.networkrail.co.uk

 

[HSTEd]

Did anything ever come of that plan to paint the sides of rails white to reduce their temperature in summer?

 

[6Gman]

Genuine question - how much was track buckling a problem in the days before continuously-welded track? I presume even welded track isn't really "continuous" and must have some expansion joints somewhere so if (as some predict) we are going to see more, hotter, summer days as global temperatures rise, is there a case for reducing the distances between these joints as track is relaid?

Those of us of a certain age will recall the debates in the early days of cwr (continuously welded rail) balancing the safety record of cwr v jointed track. There were some nasty accidents back then with cwr buckling, but equally all those rail joints on conventional track were themselves a potential source of failure.

 

[StKeverne1497]

Those of us of a certain age will recall the debates in the early days of cwr (continuously welded rail) balancing the safety record of cwr v jointed track. There were some nasty accidents back then with cwr buckling, but equally all those rail joints on conventional track were themselves a potential source of failure.

On a long run of CWR then, do they actually leave expansion gaps - maybe as some kind of "lapped" joint rather than a butt joint to remove some of the problems of the latter? (but I do miss the sound!)

I suppose it's a balance then between "normal" and "exceptional" high (and low) temperatures and whether these two figures should be under review as the climate warms and potentially extremes become more extreme.

 

[Horizon22]

Did anything ever come of that plan to paint the sides of rails white to reduce their temperature in summer?

Yep; you can see it at various critical junctions around the network, even from a passenger's seat at certain places!

 

[swt_passenger]

On a long run of CWR then, do they actually leave expansion gaps - maybe as some kind of "lapped" joint rather than a butt joint to remove some of the problems of the latter? (but I do miss the sound!)
[…]

No, I don’t believe so. I’m sure someone mentioned before that CWR can run for many miles between any S&C locations - where the individual rails must have gaps for obvious reasons.

 

[StKeverne1497]

No, I don’t believe so. I’m sure someone mentioned before that CWR can run for many miles between any S&C locations - where the individual rails must have gaps for obvious reasons.

I found that Wikipedia actually has a reasonable article on the subject (at least it looks that way to my untrained eye). There is a picture of an expansion joint too:

 

[swt_passenger]

I found that Wikipedia actually has a reasonable article on the subject (at least it looks that way to my untrained eye). There is a picture of an expansion joint too:

It’s still worth emphasising that those breathers or expansion joints are not fitted in the continuous length of CWR, but have specific uses eg “areas where CWR joins up to jointed track or to certain types of switches and crossings”. @Bald Rick explained this back in a 2019 thread here:

Continuous Welded Rail (CWR)

Of course, more expansion joints might provide relief if the SFT remains 27C. As posted previously, there are no expansion joints in CWR. Having any expansion joints makes it not continuously welded, and there would be no point in stressing it.

www.railforums.co.uk

 

[Bald Rick]

I found that Wikipedia actually has a reasonable article on the subject (at least it looks that way to my untrained eye). There is a picture of an expansion joint too:

It’s still worth emphasising that those breathers or expansion joints are not fitted in the continuous length of CWR, but have specific uses eg “areas where CWR joins up to jointed track or to certain types of switches and crossings”

and further worth emphasising that a mile of CWR will want to expand by nearly a metre in length between the coldest and hottest temperatures it is likely to experience, which is an awful lot of expansion joints. Hence why it is stressed : to absorb this expansion Without the need for expansion joints.

 

[HSTEd]

and further worth emphasising that a mile of CWR will want to expand by nearly a metre in length between the coldest and hottest temperatures it is likely to experience, which is an awful lot of expansion joints. Hence why it is stressed : to absorb this expansion Without the need for expansion joints.

Maybe we should make rails out of Invar or Inovco! Under 4" for a mile and a hundred celsius temperature swing!

And I know it would be ruinously expensive, I'm joking... sort of

 

[Bald Rick]

Maybe we should make rails out of Invar or Inovco! Under 4" for a mile and a hundred celsius temperature swing!

And I know it would be ruinously expensive, I'm joking... sort of

I hope you are!

Perhaps we should just accept that the Laws of physics are universal and that in extremes of weather some things change. It is the same everywhere.