High Track Temperature

[JamieL]

Sat at Southampton Airport Parkway awaiting a train into the city and the next train is delayed about 10mins due to "high track temperature".

Notwithstanding it isn't actually hot, and has been raining, how is this determination made? How and where is track temperature monitored?

 

[800301]

Sat at Southampton Airport Parkway awaiting a train into the city and the next train is delayed about 10mins due to "high track temperature". Notwithstanding it isn't actually hot, and has been raining, how is this determination made? How and where is track temperature monitored?

Can be monitored in various ways but can also be done as a precautionary measure, you have to remember when the sun is out it’s shining directly on the rail making it much hotter than the ambient temperature, if you left something metal outside in the sun for a while and then touched it I’m sure you’d find this out

 

[ainsworth74]

Can be monitored in various ways but can also be done as a precautionary measure, you have to remember when the sun is out it’s shining directly on the rail making it much hotter than the ambient temperature, if you left something metal outside in the sun for a while and then touched it I’m sure you’d find this out

Exactly, try touching the roof of car that's been sat in the sun. The outside air temperature might not be particularly high yet the roof of the car could be very painful to the touch because it's at a much higher temperature having sat that merrily absorbing the suns rays.

 

[JamieL]

Does not rain act as a heat sink? It just seems surprising to me that, on a warm but not hot day (22C) with regular showers, we are talking delays.

 

[Tilting007]

Sat at Southampton Airport Parkway awaiting a train into the city and the next train is delayed about 10mins due to "high track temperature". Notwithstanding it isn't actually hot, and has been raining, how is this determination made? How and where is track temperature monitored?

It is likely track disturbance such as tamping or other works have reduced the Critical Rail Temperature (CRT).

Track is fine to extremely high temps if fully ballasted, stressed and undisturbed but maintenance needs to be undertaken that will affect this.

Looking at this specific site it looks like an issue with a section of rail that was installed and not welded so clamps fitted and during an inspection the size of the gap requires a 20mph restriction.
Strange as the gap would normally close up and widen in hot weather - but that said I don’t know the full details from site.

 

[hexagon789]

Does not rain act as a heat sink? It just seems surprising to me that, on a warm but not hot day (22C) with regular showers, we are talking delays.

Rail temperature can easily be 20C above air temperature even in cloud.

Most rail in the UK is stressed for a temperature of 27C, above that the rail can be under heat stress as I understand it.

 

[furnessvale]

The highest rail temperature I ever recorded when destressing was 52C.

 

[styles]

The highest rail temperature I ever recorded when destressing was 52C.

Hope you verified this by frying bacon and eggs on the line.

 

[Bald Rick]

Does not rain act as a heat sink? It just seems surprising to me that, on a warm but not hot day (22C) with regular showers, we are talking delays.

Solar gain at this time of year is maximum, rail temps in direct sunlight will be 19-20C above ambient.

I’ve said previosuly, but I once put a hot weather speed on a line in February. (I was not very popular at all that day).

 

[JamieL]

Thanks for all the info everyone.

 

[Harpo]

Does not rain act as a heat sink?

Yes but there isn’t usually enough of it. If I recall it correctly, a rail needs more than its own weight in water to get a 10C reduction in temperature.

 

[Spartacus]

Sat at Southampton Airport Parkway awaiting a train into the city and the next train is delayed about 10mins due to "high track temperature". Notwithstanding it isn't actually hot, and has been raining, how is this determination made? How and where is track temperature monitored?

I don't know which train it was but if it's the one I'm thinking of it was a non-heat related ESR.

 

[JamieL]

I don't know which train it was but if it's the one I'm thinking of it was a non-heat related ESR.

It was a Southern service. I can't remember the scheduled time though - I was just at the station awaiting any train to Southampton Central.

 

[Spartacus]

It was a Southern service. I can't remember the scheduled time though - I was just at the station awaiting any train to Southampton Central.

Yeah, that'll be it, ESR around Cosham, nothing to do with heat (in fact a bit of extra heat might have helped prevent it!

 

[Annetts key]

In addition to the rail itself heading up from the radiation from the sun (which is heat and light), the ballast will also heat up and absorb the heat. Then re-radiate the heat. So the rails gain heat directly from the sun and from the ballast.

 

[Howardh]

Network Rail paint the rails white - still not convinced it wasn't posted on April 1! But does it work well?

Video posted 23 April showing how and why they paint the rails white

39K views · 269 reactions | Rollers at the ready! Why do we paint rails white for summer❓ ️ This spring we’ll use about 1,500 litres of white paint – the equivalent of 30,000... | By Network Rail | Facebook

Rollers at the ready! Why do we paint rails white for summer❓ ️ This spring we’ll use about 1,500 litres of white paint – the equivalent of 30,000...

www.facebook.com

This spring we’ll use about 1,500 litres of white paint – the equivalent of 30,000 square metres – for sections of the railway to help keep you moving in #hotweather:

 

[Bald Rick]

Network Rail paint the rails white - still not convinced it wasn't posted on April 1! But does it work well?

Video posted 23 April showing how and why they paint the rails white

39K views · 269 reactions | Rollers at the ready! Why do we paint rails white for summer❓ ️ This spring we’ll use about 1,500 litres of white paint – the equivalent of 30,000... | By Network Rail | Facebook

Rollers at the ready! Why do we paint rails white for summer❓ ️ This spring we’ll use about 1,500 litres of white paint – the equivalent of 30,000...

www.facebook.com

Yes it does work. Itis typically ised on ‘unusual‘ track, for example unstrengthened* / fabricated** Pointwork.

*Unstrengthened means it is not stressed or welded to plain line welded rail.

**Fabricated means the corssings are bolted together on site out of sections of rail, rather than being pre cast. Getting rarer now but theres still some out there.

 

[stuu]

Network Rail paint the rails white - still not convinced it wasn't posted on April 1! But does it work well?

Very common in northern Italy, even on plain line. I guess more needed where there is a bigger range rather than higher absolute temperatures

 

[Horizon22]

Yes it does work. Itis typically ised on ‘unusual‘ track, for example unstrengthened* / fabricated** Pointwork.

*Unstrengthened means it is not stressed or welded to plain line welded rail.

**Fabricated means the corssings are bolted together on site out of sections of rail, rather than being pre cast. Getting rarer now but theres still some out there.

Is it not also common on key pointwork as well?

 

[Bald Rick]

Is it not also common on key pointwork as well?

Key pointwork that has some unusual aspect to it, yes.

 

[D6130]

Very common in northern Italy, even on plain line. I guess more needed where there is a bigger range rather than higher absolute temperatures

Even more common in Central and Southern Italy, where the temperature range can be even greater in Spring and Autumn.

 

[Russel]

Do they have these problems in places like Italy and Spain, where they have much warmer and longer summers?

 

[hexagon789]

Do they have these problems in places like Italy and Spain, where they have much warmer and longer summers?

I would assume the track is stressed for a higher Stress Free Temperature in those countries.

 

[Bald Rick]

Do they have these problems in places like Italy and Spain, where they have much warmer and longer summers?

It’s not the high temperature, nor the length of summer.

It is the temperature range, and what work you do on the track in the run up to summer. Almost all heat speed restrictons in the UK are implemented in hot spells following work to the track. (Hence my hest speed restriiction one February, following work and a subsequent huge temoerature range)

In hot countries, they tend to avoid working on the track in the run up to summer.

I would assume the track is stressed for a higher Stress Free Temperature in those countries.

Typically not, a couple of places a degree or two higher but that’s it.

 

[Spartacus]

In many places they have to restress the track, twice a year, at quite a cost, and not without disruption, and it still doesn't exactly solve the problem. I can't remember the figures but last year I tracked down the number of derailments caused by heat in the USA and it was quite remarkable, and that included instances of joints being pulled apart through shrinkage in cold weather, a potentially much more dangerous issue.

 

[stuartl]

Network Rail paint the rails white - still not convinced it wasn't posted on April 1! But does it work well?

Video posted 23 April showing how and why they paint the rails white

39K views · 269 reactions | Rollers at the ready! Why do we paint rails white for summer❓ ️ This spring we’ll use about 1,500 litres of white paint – the equivalent of 30,000... | By Network Rail | Facebook

Rollers at the ready! Why do we paint rails white for summer❓ ️ This spring we’ll use about 1,500 litres of white paint – the equivalent of 30,000...

www.facebook.com

Painting things white certainly does help, if you remember black body radiation in school physics lesson. I used to have a south west facing back door painted black with a white surround. When the sun came out it soon got very hot but the white frame stayed cool. Our local council installed large concrete pebbles for people to sit on. Some were pale grey , others dark brown. They had to put signs on the brown ones warning people that they could be very hot.

 

[MarkyT]

Key pointwork that has some unusual aspect to it, yes.

Switched diamonds for example, which are notoriously difficult to keep in adjustment and are prone to detection failure with temperature changes. I first saw white rail painting on some switched diamonds around the Southern Region, in maybe the late 90s or early 2000s.

 

[duffield]

Does the white paint need applying just annually, or more, or less frequently?

 

[Ploughman]

How long before the white paint is turned brown?

 

[Harpo]

Switched diamonds for example, which are notoriously difficult to keep in adjustment and are prone to detection failure with temperature changes.

Yep. I’ve still got the scars of a 5000 minute incident.