Speed Restrictions due to Heat

[broadgage]

If the worst problems are on the approaches to Waterloo, perhaps it might be worth consider spraying water to cool the track.

Not from a train, due to the concerns about pathing etc raised in an earlier post.
What about something as simple as garden sprinklers on signal gantries or lineside structures. This would wet the whole area, and by evaporation should produce significant cooling of both the rails and the immediate surroundings.
I doubt that thermal shock would be a problem, since the water in the supply pipes would become warm when the equipment was not in use, and the first water applied would be warm or hot, cooling over some minutes as the hot water was replaced with cold from the mains. And anyway it rains in the Summer.

 

[Monty]

Ah - so it's not down to the heat. It all depends on how busy the line is.

Well, that's sorted then!

It's a contributory factor yes, as are a lot of other variables.

 

[Requeststop]

I am guessing here, but I would imagine the metal mix in French rails is different as they have average higher temperatures than the UK. Ours have to endue a generally harsher winter so are more geared to that. Happy to be corrected if I'm wrong.

French Alpine areas?

 

[edwin_m]

What about something as simple as garden sprinklers on signal gantries or lineside structures. This would wet the whole area, and by evaporation should produce significant cooling of both the rails and the immediate surroundings.
I doubt that thermal shock would be a problem, since the water in the supply pipes would become warm when the equipment was not in use, and the first water applied would be warm or hot, cooling over some minutes as the hot water was replaced with cold from the mains. And anyway it rains in the Summer.

Interesting thought. There was a water spray on the track at Barnt Green a few years ago (may still be there) but it was to reduce rail squeal on the curve rather than anything to do with temperature.

Another reason the thermal shock wouldn't be a problem is that the water would be sprayed before the rail got too hot. But I think there might be a problem with the third rail?!

I read in Modern Railways recently that some of the track components at Waterloo are to designs that date from the 1930s, so perhaps this is why they are less resilient than on other routes.

 

[455driver]

Ah - so it's not down to the heat. It all depends on how busy the line is.

Well, that's sorted then!

Thank you for being so selective in your understanding. :roll:

Its to do with the fact that the track cannot be stressed due to the curvature and points, but I wouldnt expect you to understand.

 

[Eagle]

Who knows how long it will last

I'm thinking about an hour or two tops. So unless we're going to send the coolant trains out several times a day it's a nonstarter.

Ah - so it's not down to the heat. It all depends on how busy the line is.

Well, that's sorted then!

Aha, so the solution is to run fewer trains then! That's why there are so many cancellations at Waterloo today :P

 

[al78]

I am guessing here, but I would imagine the metal mix in French rails is different as they have average higher temperatures than the UK. Ours have to endue a generally harsher winter so are more geared to that. Happy to be corrected if I'm wrong.

Really?

The continent is far more exposed to bitterly cold easterlies or NEly's than the UK, not having the moderating effect of the North Sea upwind.

The south of France will in general be milder than the UK in winter but the north is very similar if not a bit colder.

 

[valenta]

For what it's worth, the T+W metro imposed speed restrictions due to the heat today.

 

[martybabes]

Thank you for being so selective in your understanding. :roll:

Its to do with the fact that the track cannot be stressed due to the curvature and points, but I wouldnt expect you to understand.

My pleasure.

And no, I don't. But then, I'm not a train driver!

 

[tsr]

For what it's worth, the T+W metro imposed speed restrictions due to the heat today.

As did Croydon's (or, as some now like to say, London's) Tramlink.

 

[Bald Rick]

Cue the rail haters and anti-rail haters (and the anti-anti-rail haters et al)

So why doesn't the TGV run at 35 kph on hot days? I remember leaving Avignon on a hot day and we reached Paris on time after travelling at a good old lick. And it is not as hot as Arizona in the south of France every day - I've been there (Provence) on days when it is cool, and days when it is very windy (as in Mistral windy).

Maybe we should take a tip and learn from from Les Grenouilles...

We do, and you won't see heat speed restrictions on HS1.

We run it just like the French do, i.e with a long overnight no trains period so that any rerailing is welded and stressed before the start of service next day. Whereas on our 'classique' network we like to run trains after 2300 and before 0600.

Similarly any disturbance of the ballast - either reballasting or tamping - is done in conjunction with a dynamic track stabiliser (DTS), which consolidates the ballast sufficiently that the critical rail temperature at which a speed restriction is applicable is unlikely. The LGVs are built such that DTSs can be used everywhere. On our classique network, DTSs cannot be used anywhere near bridges, tunnels, platforms or weak embankments, which rules out almost all of London and a good proportion of the rest of the country (except HS1 naturally).

Also, the French do not risk reballasting their LGV in summer. But then having millions of Euros of plant standing around doing nothing for a third of the year is what makes them the super-efficient railway they are (is this right?)

A good read on this subject is the hot weather precautions chapter of Ellis & Copes' book on Plain Line maintenance, which explains all in relatively plain language.

 

[Trog]

On our classique network, DTSs cannot be used anywhere near bridges, tunnels, platforms or weak embankments, which rules out almost all of London and a good proportion of the rest of the country.

That is something of an exageration, bridges are rated for how they will stand up to a DTS and most of them are OK. Weak embankments and platforms make up a rather small percentage of the national network and tunnels are not a problem with heat speeds as for some reason they suffer from a certain lack of sunshine.

 

[Bald Rick]

That is something of an exageration, bridges are rated for how they will stand up to a DTS and most of them are OK.

Not in South London !

 

[Juniper Driver]

These heat waves don't last long though so the problem will be over by the end of the month and we will have something to bash the railways over.

 

[Trog]

Not in South London !

It's probably an age thing our bridges being older, would have been better built than those on the tramway. Also our weaker bridges are more likely to have been replaced over time, due to our greater weight of traffic. We have a through siding carrying over 25 EMGTPA for example.

Brick arches and concrete bridges are also often a better bet than metal spans.

 

[Blindtraveler]

dont think its been mentioned here but heat related points and signal problems at Edinburgh yesturday PM Made a good job of screwing up the evening peek with delays of up to 50 mins and many alterations. Speed restrictions West of Haymarket didnt make the job any easier but rail staff coped well and for the benited users of the newly reglazed Waverley NR Provided free water.
Think the ECML side did ok with only a few holdups with conjestion at EDB But the 16:52 Voyager down the WCML Was rather late. Heat related restrictions on Glasgow to Ayr too. ↲

good bit cooler here today so any jurno wanting railway chaos as britain bakes will have to look further away.↲
↲

 

[michael769]

Yeah I went through Waverley at about 5:45 and it was pretty bad with very single service delayed and no platforms allocated.

They did seem to be making a pretty concerted effort to get folks moving though and onto the right trains, and also to run as many services to as many destinations as they could, so I certainly have to give credit to everyone involved. Alas by that time there was no signs of any water being handed out that I saw.

Getting home only 30mins late was pretty good going giving the circumstances.

 

[Teaboy1]

OK i stand corrected, my error!
Here are the facts
Steel Linear Coeff of Expansion [metric] = 10.8 e-6 m / degK, therefore a 30m length of rail heated from 0 degC > 100 degC will expand;
10.8 e-6 x 30 000 (mm) x 100 degK = about 32.4 mm [seems reasonable] but thats a bit excessive.
So 1Km of rail heated up from 10 degC > 40 degC will grow;
10.8 e-6 x 1 e6 (mm) x 30 degK = about 324 mm [about 1 ft, again seems reasonable] so quite a bit of expansion to accomodate. As we know any steel in direct sunlight dont half get hot, hotter than the air temp so again I expect 40 degC is quite easily achieved mid-day.
So can fully welded rail really handle that amount of stain and growth??

and please dont pick me up if I am only a few mm out in my calc, its just a rough back-of-fag-packet-calc!!

 

[HSTEd]

You could make the rails out of special low-expansion steels, but that would probably cost quite a lot.

 

[Trog]

The stress involved in rail steel is approximately one tonne of tension or compression for every degree C the rail moves off its natural temperature.

Its natural temperature in railway speak is the temperature at which a rail constrained by its installation in the track is at the same length as it would be if it was lying in the cess free to move as it expanded and contracted.

 

[westv]

Speed restrictions due to heat is something that I never heard of during over 30 years of commuting until relatively recently - or is my memory failing me?

 

[Bald Rick]

Speed restrictions due to heat is something that I never heard of during over 30 years of commuting until relatively recently - or is my memory failing me?

Either memory failure or more likely we didn't dare use it as an excuse...

 

[HSTEd]

Perhaps one of the advantages of putting trains in tunnels, keeps the temperature conditions far more stable.

More crossrail esque services!

 

[AndyPJG]

You could make the rails out of special low-expansion steels, but that would probably cost quite a lot.

Wear resistance and strength are more important properties.

 

[GB]

Speed restrictions due to heat is something that I never heard of during over 30 years of commuting until relatively recently - or is my memory failing me?

There is a lot more continuously welded rail these days than there was 15-20 years ago.

 

[westv]

There is a lot more continuously welded rail these days than there was 15-20 years ago.

Wel this was south to central London and Essex to central London.

 

[island]

If the worst problems are on the approaches to Waterloo, perhaps it might be worth consider spraying water to cool the track.

Not from a train, due to the concerns about pathing etc raised in an earlier post.
What about something as simple as garden sprinklers on signal gantries or lineside structures. This would wet the whole area, and by evaporation should produce significant cooling of both the rails and the immediate surroundings.
I doubt that thermal shock would be a problem, since the water in the supply pipes would become warm when the equipment was not in use, and the first water applied would be warm or hot, cooling over some minutes as the hot water was replaced with cold from the mains. And anyway it rains in the Summer.

I don't think watering third rails is a good strategy...

 

[Cliveblackpool]

High pressure pumps, and misting spray nozzles, they could have a nice cool cloud over Waterloo!!

 

[Ploughman]

How many DTS machines are there available in the UK now?
They did suffer a drastic reduction in numbers in the last few years I think.

 

[Bald Rick]

How many DTS machines are there available in the UK now?
They did suffer a drastic reduction in numbers in the last few years I think.

Good question. Balfours have 2, and there are a couple of Automatic Finishing Machines (AFMs) that are worked with the High Output Ballast Cleaners - AFMs are combined regulators / DTS. And I think that's it, although happy to be corrected.