Railway disruption due to heat

[Gwiwer]

The issue is about stressing the rails so they don't buckle at high temperatures, but aren't under excessive tension at low temperatures.  It is stated that there is a tradeoff between one and the other. 

 

However there are plenty of places with railways that also have much wider temperature ranges than Britain does.  What is done differently so they can cope (other than slab track, which most of them clearly don't have)?  Closer/heavier sleepers, more ballast, heavier rails (which would probably make things worse), breather switches?.  Or do they also impose restrictions but we just don't hear about them?

 

Now living a "hot place" I feel qualified to offer some sort of response.

 

Australia gets heat buckles.  It suffers derailments and overhead problems, loss of point detection and signal failures all arising from heat.  Air conditioning failures mean passenger rolling stock is taken out of service leaving folks standing on overheated, overcrowded platforms at peak times.  Australia is also - in many areas - way behind the UK in terms of installing deep ballasted CWR on concrete or metal sleepers.

 

What is done can vary for absolutely nothing through imposition of speed restrictions (for which you might see the term WOLO used) and painting of rails white.  The latter was an idea imported from Britain, ironically, and does reduce the railhead temperatures by a small amount.   Sources vary but I have seen the range quoted as between 2 and 10 Celsius degrees.

 

The older and lighter-laid road bed means that speed restrictions may not have the same effect that they do in the UK but they can still cause hours of lateness.  That is in turn enough to upset the rostering of, for example, the Sydney - Melbourne XPT trains which will usually be turned back to the north from Albury and road coaches provided through Victoria.  

 

Customers are often advised by means of station announcements to carry water and to alight from a train and sit in shade if feeling unwell in the heat.  In Melbourne the hottest days (around 43C) are often accompanied by a gale force wind as well which rips the moisture right out of you and dehydrates like nothing else I know.  Those winds also drive the wild fires we suffer from at the same time of year.

 

Torrential rain can occur anywhere as can tropical cyclones in the northern part of the country.  Queensland is particularly susceptible and is also ready with new ballast, track and overheads to effect quick repairs.  In some cases many kilometres of line are washed out in one event including bridges.  Temporary replacement bridges go up remarkably quickly as well in a land where the wooden trestle is alive and well.

 

On the whole the travelling public bears it as a day in the life and of course with a few grumbles about being late for dinner or missing a bus somewhere.  Freight may be held up for a few days or a couple of weeks in severe cases.  Loco crews stuck in the outback are usually able to reach at least a point of refuge such as a loop and sometimes the next town (however small it might be - some have a population in single figures), park the train and be collected by road vehicle for transport back home.  The train is collected again when the line reopens.  Almost all Australian railways have a 4-wheel drive track alongside them for vehicle access, maintenance and repairs.

[Rivercider]

When I first started on BR I spent a few months as a junior CO1 clerk in the Permanent Way Clerical  section of the Divisional Civil Engineers Office in Bristol.

One of my jobs each day was to phone round the the Permanent Way section offices to get the daily rail temperature from them, which I recorded.

 

Whether this practice was carried out elsewhere I do not know but my father, who had worked in that section before me, told me that the reason

the Bristol Divisional Civil Engineer was so keen on rail temeratures followed the Somerton derailment of 13th June 1969 which was due to a buckled rail.

http://www.railwaysarchive.co.uk/eventimages.php?eventID=127&imageID=434

He also told me it was thought it was lucky the derailment occurred where it did in a cutting as a short distance later the line ran onto an embankment,

where the consequences could have been much more serious,

 

 

edit - in fact it seems Somerton was one of three similar accidents that occurred in 1969 which lead to changes in rules for laying and maintenance of CWR

 

cheers,  

[Fat Controller]

Something i've learned from RMWeb is the practice of painting the sides of switch/crossing rails white to help lessen the effect of heat on the formations.

Is this used on any plain line? - I'd guess probably not, as you'd have to know which lines would be likely to be affected, but just wondered.

Is there a defining criteria or is it just a case of treating areas that are already known to have caused problems?

I think I've mentioned it before, but the Bologna- Milano high-speed line has white-painted rail sides for all the length parallel with the autostrada.

[Fat Controller]

When I first started on BR I spent a few months as a junior CO1 clerk in the Permanent Way Clerical  section of the Divisional Civil Engineers Office in Bristol.

One of my jobs each day was to phone round the the Permanent Way section offices to get the daily rail temperature from them, which I recorded.

 

Whether this practice was carried out elsewhere I do not know but my father, who had worked in that section before me, told me that the reason

the Bristol Divisional Civil Engineer was so keen on rail temeratures followed the Somerton derailment of 13th June 1969 which was due to a buckled rail.

http://www.railwaysarchive.co.uk/eventimages.php?eventID=127&imageID=434

He also told me it was thought it was lucky the derailment occurred where it did in a cutting as a short distance later the line ran onto an embankment,

where the consequences could have been much more serious,

 

 

edit - in fact it seems Somerton was one of three similar accidents that occurred in 1969 which lead to changes in rules for laying and maintenance of CWR

 

cheers,  

I remember a spate of plain-line derailments at about that time, attributed to rail buckling in the heat; one thing I noticed was that, very quickly, ballast shoulders began to be built-up, rather than sloping away to the cess.

[dj_crisp]

A very interesting thread. When i got home at about 6 the temperature in South West London was a warm 37.5... that reading was in the shade and north facing and the hottest I've seen.

 

A rather warm day! No surprises if there were a few issues around the country.

[Mike Storey]

The Chairman of SNCF (French Railways) had to apologise yesterday for the severe detriment to the quality of people's lives, if I have translated the report adequately (I only glimpsed it over someone's shoulder) due to the major disruption to train services across France caused by the heat and by thunderstorms. 

[kenw]

I'll tell you whats happened to us, we're all petrified about being sued.... In the good ole days, we just accept it and got on with it, now we need to find someone to blame.

 

And with good reason, continuing to run trains normally at full linespeed when there's a danger of rails buckling under heat WOULD BE reckless. Or go back to the "good ole days" with numerous derailments as reported in the above posts.

 

Part of the problem with public perception of rail problems, I noticed Tuesdays headline in a London paper (ES or Metro) with the inevitable "wrong sort of"...heat

20 years after BR, and they STILL can't come up with anything more original than "wrong sort of <anything>" inevitably reported to make OUT it's some sort of made up excuse. (and how many of their 'readers' even still know where this came from?)

 

Wrong sort of heat? NO!! 

More like..

WRONG SORT OF JOURNALISTS !!

[Fat Controller]

The Chairman of SNCF (French Railways) had to apologise yesterday for the severe detriment to the quality of people's lives, if I have translated the report adequately (I only glimpsed it over someone's shoulder) due to the major disruption to train services across France caused by the heat and by thunderstorms. 

Someone from SNCF apologise for something? It's a portent of something dreadful....

[coachmann]

Maybe we weren't informed of life's minutei in days gone by or maybe traditional short rail lengths had a lot going for them in heat. All I remember is a typical Gaumont British News would have a be full of well spoken jollity about the British making the most of a hot spell and all accompanied by rousing marching music..................... wotto old boy.

[Bon Accord]

And with good reason, continuing to run trains normally at full linespeed when there's a danger of rails buckling under heat WOULD BE reckless. Or go back to the "good ole days" with numerous derailments as reported in the above posts.

 

Part of the problem with public perception of rail problems, I noticed Tuesdays headline in a London paper (ES or Metro) with the inevitable "wrong sort of"...heat

20 years after BR, and they STILL can't come up with anything more original than "wrong sort of <anything>" inevitably reported to make OUT it's some sort of made up excuse. (and how many of their 'readers' even still know where this came from?)

 

Wrong sort of heat? NO!! 

More like..

WRONG SORT OF JOURNALISTS !!

 

The only perception problem here is that which causes otherwise sensible people to slavishly believe that unless any person with even the most minimal accountability for anything (real or imagined) is living in continual state of fear of "what if" and then correspondingly takes that "caution" into everything they do - work related and otherwise - then death and destruction will abound.

[trisonic]

Trains in the South West USA run pretty normally in the Summer. The shade temperature routinely hit 116f around Phoenix and I paced a BNSF freight of 1.2 miles long doing 70 mph along the transcon west of Gallup in similar temperatures. They don’t paint the track white either.

The secret is to pre-heat the track whilst laying it.... Steel does not get soft at these kind temperatures...

 

 

 

Best, Pete.

[Dagworth]

Trains in the South West USA run pretty normally in the Summer. The shade temperature routinely hit 116f around Phoenix and I paced a BNSF freight of 1.2 miles long doing 70 mph along the transcon west of Gallup in similar temperatures. They don’t paint the track white either.

The secret is to pre-heat the track whilst laying it.... Steel does not get soft at these kind temperatures...

 

 

 

Best, Pete.

But do they suffer the same levels of cold?

 

Andi

[Mike Storey]

Trains in the South West USA run pretty normally in the Summer. The shade temperature routinely hit 116f around Phoenix and I paced a BNSF freight of 1.2 miles long doing 70 mph along the transcon west of Gallup in similar temperatures. They don’t paint the track white either.

The secret is to pre-heat the track whilst laying it.... Steel does not get soft at these kind temperatures...

 

 

 

Best, Pete.

 

Rail is "pre-heated", or rather mechanically stressed to simulate this, all over the UK and Europe before or while it is laid. But it is stressed to the median of the historic range (to the 3rd quartile IIRC), or average temperature for that part of the world, and the temperatures currently being experienced in Western Europe are reaching well outside that range.

[96701]

Trains in the South West USA run pretty normally in the Summer. The shade temperature routinely hit 116f around Phoenix and I paced a BNSF freight of 1.2 miles long doing 70 mph along the transcon west of Gallup in similar temperatures. They don’t paint the track white either.

The secret is to pre-heat the track whilst laying it.... Steel does not get soft at these kind temperatures...

 

 

 

Best, Pete.

No matter where you live on this planet, you can't alter the coefficient of expansion of steel.

Product                                         Linear Temperature ExpansionCoefficient

                                                                                             - α

                                                                   (10^-6 m/(m K))^*         (10^-6 in/(in R))^*

Steel                                                                     12                          6.7

 

When an object is heated or cooled, its length changes by an amount proportional to the original length and the change in temperature.

 

^*  m/m = meter per meter, in/in = inches per inches

Most values are based on temperature 25 ^oC (77 ^oF).

• t_K = t_C + 273.16
• t_R = t_F + 459.67  
• 1 in (inch) = 25.4 mm
• 1 ft (foot) = 0.3048 m

Editted to try to get the table right. Actually copied from here: http://www.engineeringtoolbox.com/linear-expansion-coefficients-d_95.html

[kenw]

Trains in the South West USA run pretty normally in the Summer. The shade temperature routinely hit 116f around Phoenix and I paced a BNSF freight of 1.2 miles long doing 70 mph along the transcon west of Gallup in similar temperatures. They don’t paint the track white either.

The secret is to pre-heat the track whilst laying it.... Steel does not get soft at these kind temperatures...

 

As was stated in previous posts, the rails are pre-stressed. This is done though to take account of conditions normally expected to be experienced, and recent temperatures have been above normal, even for this time of year ( "hottest July day on record" ).

A balance needs to be struck here though, remember steel will also want to contract in freezing conditions - over-stretch to allow for exceptional hot conditions, and the result's even greater problems in freezing conditions - ie broken rails !!

 

And no, steel does't get soft, it expands which can result in buckled rails

[kenw]

The only perception problem here is that which causes otherwise sensible people to slavishly believe that unless any person with even the most minimal accountability for anything (real or imagined) is living in continual state of fear of "what if" and then correspondingly takes that "caution" into everything they do - work related and otherwise - then death and destruction will abound.

 

That depends very much on the context, and as the context under discussion is the risk of buckled track due to heat expansion, then yes, if the cautious approach wasn't taken then the likely result would be death and destruction would abound

[The Stationmaster]

According to a report in our local paper the Western was experiencing rail temperatures of 50+ centigrade yesterday hence some 20mph restrictions between Reading and Paddington.

[kenw]

According to a report in our local paper the Western was experiencing rail temperatures of 50+ centigrade yesterday hence some 20mph restrictions between Reading and Paddington.

 

Another point often seemingly overlooked.

It's not just about a few degrees extra in ambient temperature, a polished steel rail, outdoors in direct strong sunlight, will absorb heat and reach temperatures considerably hotter than just the ambient temperature.

But then perhaps some people haven't noticed this effect in their car interiors on returning when they've been parked in the sun?

[david.hill64]

I remember a spate of plain-line derailments at about that time, attributed to rail buckling in the heat; one thing I noticed was that, very quickly, ballast shoulders began to be built-up, rather than sloping away to the cess.

Building up the ballast shoulders is a sensible thing to do.

 

The natural motion of a wheelset along the track is sinusoidal: this gives rise to lateral forces as well as the obvious vertical (vehicle weight) and longitudinal (traction and braking) forces. This lateral load naturally increases as vehicle speeds rise. A semi-empirical equation was developed by Prud'homme of SNCF to describe the maximum permitted lateral load that a vehicle could safely impart of a track. This is given by the equation:

 

L = 0.85(10+V/3) where L is the lateral load limit and V is the axle load.

 

The limit is conservative and where ballast shoulders are used - which increase the lateral stability of the track - the 0.85 multiplier can be ignored.

 

I think this work came about following the French high speed runs in the 1950's which caused severe track distortion.

 

These days with a much better understanding of wheel-rail interaction, computer programs such as BRR's Vampire software give much better understanding of the forces generated and how they are reacted by the track.

 

The other longitudinal force comes from rail temperature. As others note, rails are 'destressed' when installed by stretching them so that at a nominal temperature they are stress free (I cannot remember what this is - 28 degrees has been suggested above). Once above this temperature the rails are in compression. IF you take a piece of model rail and push the ends together eventually it will buckle. If you get just before this point and ask somebody to tap the side it will buckle sooner. This is exactly the situation at 12" to 1' scale.

 

Note the importance of speed in this: the plains of the US will see very large temperature variations, but it is a slow speed railway (even if axle loads are much greater than in Europe) and the rail section is heavier which would allow the rails to be destressed to a higher temperature and give greater resistance to buckling.

[Gwiwer]

Temperature range is definitely an issue in some places. Pre-tensioning is fine and does what it should.  I discussed above the air temperature normally reached across many parts of Australia in the summer which is in the low to mid 40s Celsius.  In the outback it can occasionally top 50 which can affect the cross-continental routes between Adelaide and Perth or Darwin.  But in the winter it can be cold.  Canberra, the national Capital, regularly wakes to temperatures of -3C having endured as low as -6C overnight.  The Victorian city of Ballarat is another which lies in a mountain basin and thus holds cold air and endures very low temperatures.  The air temperature range is therefore between around -6C and +43C across the year.  Both Canberra and Ballarat have busy railway lines which suffer from weather-related defects at times.  The first few miles north out of Canberra twist through mountains and gorges where exfoliation (Google it ) causes rockfalls and heavy rains cause landslides to add to the problems.  But it's quite spectacular and worth the ride if you're in the area.

 

A question for the engineers.  I have heard it said among railwaymen (including women) that the interplay of cooler wheels on hot rails is what is most likely to initiate a buckle rather than just the rail sitting out in the baking sun.  I'm not sure of there's any degree of truth in that.  There seems to be some logic behind it however as if your railhead is at 50C and has gradually reached that allowing all track components to expand within the limits of the formation and you then run a train over it you could be placing many tons of stress upon heated rails from wheels which can be much cooler and are effectively hitting the hot railhead with shocks of cold.  I understand that running trains more slowly might be in part to ameliorate this effect as well.  What are the engineering thoughts on this?

[david.hill64]

A question for the engineers.  I have heard it said among railwaymen (including women) that the interplay of cooler wheels on hot rails is what is most likely to initiate a buckle rather than just the rail sitting out in the baking sun.  I'm not sure of there's any degree of truth in that.  There seems to be some logic behind it however as if your railhead is at 50C and has gradually reached that allowing all track components to expand within the limits of the formation and you then run a train over it you could be placing many tons of stress upon heated rails from wheels which can be much cooler and are effectively hitting the hot railhead with shocks of cold.  I understand that running trains more slowly might be in part to ameliorate this effect as well.  What are the engineering thoughts on this?

 

I think it's nothing to do with the wheels being cooler - indeed wheels are often hotter than rails due to braking effects, particularly for tread braked wheels or where cheek mounted disc brakes are used. The effect is because of the lateral forces generated by the motion of the wheel along the rail. The higher the speed the higher the force, the more likely to induce a buckle, particularly if the rail is in compression due to heat..

[jjb1970]

It is a very British thing to wail about how terrible things are here and imagine that everything works splendidly everywhere else in the world. You cannot alter the simple science of thermal expansion and contraction. Where you have a stable environment then you can stress the rails for whatever temperature you like but in European countries with a major temperature swing across the seasons from significantly sub-zero to rail temperatures of 50C then swell and contraction is inevitable and we just have to accept that. There are some mitigation measures as offered here but ultimately any long bit of steel or any other metal will expand when hot.

[Gwiwer]

 

 

 ultimately any long bit of steel or any other metal will expand when hot.

 

When the railway was built from Alice Springs to Darwin in the last years of the 20th Century it was calculated by someone with more time on their hands than was entirely necessary that if the rails were free to expand in the linear dimension only then on a hot day they would extend the new railway some three miles out to sea!

[brushman47544]

I did have a laugh today whilst looking at train running disruption due to weather when Arriva Trains Wales posted that a Fishguard to Carmarthen train was delayed due to overhead line problems.  I was amused because the service was (a) a DMU and over 100 miles from the nearest OHLE.  Of course, I twigged what had really happened was a late running Manchester to Wales service, which had been delayed by the knock-on disruption caused by the OHLE failure in the Manchester area, must have been forming the service but it did rather suggest someone at ATW had been a bit too quick with the cut and paste command instead of posting "delayed due to late incoming service" or some such.

 

Either that or Carmarthen has slipped into a parallel dimension where the GW main line electrification is complete and has been extended to Fishguard.

 

Nothing gets my goat more than when I hear the announcement "delayed due to late incoming service" when a train is late. It's like saying today is Tuesday because yesterday was Monday. If they use this, then they should also say why.

[Fat Controller]

Just to prove that it's not just UK railways that suffer, here's a piece from France's Fr3 dated 29/6/2015:-

es cheminots sont sur le qui-vive : l'annonce, pour toute la semaine, de températures élevées, ils le savent, signifie "apparition de problèmes techniques" supplémentaires sur un réseau déja très fragile ces dernières années.

'Lorsque le soleil brille très fort, que les températures grimpent haut, le métal, donc les rails mais aussi les fils électriques, les caténaires, "gonfle", se dilate ou se déforme. Et les ennuis commencent.
" Lorsque la température au rail dépasse les 45°C, dit la SNCF, une vigilance accrue et des limitations de vitesse dans certaines zones sont nécessaires pour éviter les déformations de voie." Autrement dit, dans ces périodes, les cheminots chargés des voies augmentent leurs contrôles visuels et manuels des rails. Mais il n'est pas possible de faire diminuer la température d'un rail dilaté. ce qui signifie qu'en cas de trop forte déformation, il faut ralentir le trafic pour éviter tout risque, voire arrêter la circulation. Ce week-end déjà, le RER C a subi des ralentissements importants, donc des retards.'

'Whilst the sun shines very strongly, so that temperatures climb upwards, metal, including the rails, but also electric cables (catenary) 'inflate', either expanding or distorting. And then the problems start..

"Whilst the temperature of the rail exceeds 45º", said SNCF, "increased vigilance and speed restrictions in certain areas are necessary to avoid distortion of the track" In other words, during these periods, the railway staff responsible for the track increase their visual and physical monitoring of the rails. But it isn't possible to reduce the temperature of an expanded rail, which means that, in the case of an excessive distortion, it is necessary to slow down traffic to avoid any risk, or even to suspend services. Already, this weekend, RER Line C has suffered serious speed restrictions, causing delays'