Heatwave July 2022

[whole diary]

[ChrisB]

The areas that might get 40 degree heat aren’t generally the same areas that get sib-zero. Russia being one….abd generally France.

[IndustryInsider]

The areas that might get 40 degree heat aren’t generally the same areas that get sib-zero. Russia being one….abd generally France.

A combination of that, the less developed and intensive rail services generally in most of those countries and the fact there often is disruption, but we just don’t get to hear about it.

The Clarkson tweet earlier this week springs to mind:  https://www.independent.co.uk/arts-entertainment/tv/news/heatwave-uk-jeremy-clarkson-france-b2125426.html?amp

[Electric train]

How do they cope overseas ? Many places have higher Summer temperatures AND lower winter temperatures than does the UK^▸ (United Kingdom). They have railways.

Would you like to name half a dozen?

France
Ukraine
Central states of the USA.
Russia.
And many other others, generally places well inland and therefore distant from the moderating effect of oceans.

Most of them have regional difference, you cannot compare due to the size of the USA and Russia to the UK

[PhilWakely]

The areas that might get 40 degree heat aren’t generally the same areas that get sib-zero. Russia being one….abd generally France.

Crossing the Gobi Desert back in May 2012 at about midday..... 


(I suspect there may have been a fault in the thermometer!)

[PrestburyRoad]

In my view, all new railway rail infrastructure should be designed for an air temperature of 45 degrees, or a little more than the records set today. Whilst todays temperatures are exceptional, I suspect that they will become more common.
30 degrees is likely to be the new norm in Summer, with over 40 degrees reached if not every year, at least every few years.

Wouldn’t that then cause problems in the Winter when it comes to track?  A cold winter would then see the track contract so much it’ll rip itself apart. 

How do they cope overseas ? Many places have higher Summer temperatures AND lower winter temperatures than does the UK^▸ (United Kingdom). They have railways.

I believe that in some countries with an extremely very high range they have to re-tension the tracks each spring and autumn, so that in the summer the rails are a bit shorter and in the winter a bit longer.  Doing that in the UK would be a lot of work and expense and I doubt it would be funded.

[onthecushions]

I asked a Swedish colleague about this and his reply was that while their railways do have more in the way of snowploughs and resilience etc, it is generally accepted that extreme weather requires compromise in activities rather than complaints. They expect c12 hours of disruption and adapt accordingly. Perhaps our mild climate has led us to believe that we can travel and work quite independently of nature and that its is Government's fault if we can't.

OTC

[GBM]

Is this a first?
05:03 Penzance to London Paddington due 09:55
05:03 Penzance to London Paddington due 09:55 will be started from Plymouth.
It will no longer call at Penzance, Redruth, Truro, St Austell, Bodmin Parkway, Liskeard and Saltash.
This is due to severe weather earlier today.
Will be formed of 2 coaches instead of 5. First class not available.

No trolley then! 

[JayMac]

Is this a first?
05:03 Penzance to London Paddington due 09:55
05:03 Penzance to London Paddington due 09:55 will be started from Plymouth.
It will no longer call at Penzance, Redruth, Truro, St Austell, Bodmin Parkway, Liskeard and Saltash.
This is due to severe weather earlier today.
Will be formed of 2 coaches instead of 5. First class not available.

No trolley then! 

Looks like the original alteration was to run a Class 150 from PNZ to PLY^» (Plymouth - next trains) instead of the booked 5 car Class 802. That Class 150 then got cancelled. Due to be 2x 5 car Class 802 onward from PLY. 802011 + 802018 came off Laira around 0530. Sitting at Lipson Jcn currently, waiting for a path into PLY.

Educated guess is yesterday's disruption meant no 802 available at PNZ this morning.

[grahame]

Echo of earlier concerns here - questions of railways in the heat

1. Are the railways able to operate during the heat

2. Are the railways damaged by the heat

From https://www.bbc.co.uk/news/business-62234461

Repair work is ongoing across the UK^▸ (United Kingdom)'s rail network, and Network Rail said it has launched a new taskforce to investigate how the railway can become more resilient in the wake of the heatwave.

[stuving]

Repair work is ongoing across the UK^▸ (United Kingdom)'s rail network, and Network Rail said it has launched a new taskforce to investigate how the railway can become more resilient in the wake of the heatwave.

That task force looks rather like the last one - set up post-Carmont, top report on resilience against climate change in general, but focused on heavy rain rather than heat. I was wanting to look at their final report (which I think came out in March 2021) to see if it did move on to the heat issue, but I can't find it. There is a DfT^» (Department for Transport - about) link to an NR^» (Network Rail - home page) page with that title (Resilience of rail infrastructure: final report), but it's not got the final report itself. Has anyone seen it?

[stuving]

Repair work is ongoing across the UK^▸ (United Kingdom)'s rail network, and Network Rail said it has launched a new taskforce to investigate how the railway can become more resilient in the wake of the heatwave.

That task force looks rather like the last one - set up post-Carmont, top report on resilience against climate change in general, but focused on heavy rain rather than heat. I was wanting to look at their final report (which I think came out in March 2021) to see if it did move on to the heat issue, but I can't find it. There is a DfT^» (Department for Transport - about) link to an NR^» (Network Rail - home page) page with that title (Resilience of rail infrastructure: final report), but it's not got the final report itself. Has anyone seen it?

On closer examination, the "update report" listed and linked in that page must be the final report. Maybe they reckoned this subject is too big for any report to claim finality. Certainly in this case, as in the interim report, the top level description says "an assessment of the impact of extreme weather on the resilience and safe performance of the railway". But immediately it starts to limit that to earthworks, and they are at risk from rain more than heatwaves. So another chapter has to be written now ...

[stuving]

Of the two main heat effects, OLE^▸ (Overhead Line Equipment, more often "OHLE") sag is the more tractable. In principle, temperature range is just a  parameter fed into the design process, and if you make it a bit bigger you just get a slightly different set of design rules. The obvious free parameter you can change is the maximum wire run length: on those Series 1 figures, reducing that from 1500 m to 1400 m would allow about 5 degrees more temperature range.

Tensioners with a greater adjustment length might work in some cases, but that increases the along-track movement of the wires. All the things bolted to the wires - registration arms in particular - must be able to cope with this extra movement. I suspect the registration arms would not allow much more than 1 m of movement. For the same increase from 74 to 79 K, a 1 m adjustment has to go up by 65 mm.

As a practical response to the current situation, you could look at any places where loss of tension has happened and work out why. If it's a set-up issue, sort it; if it's a place where the wires get very hot for whatever reason and the wire run is long, split that one into two shorter ones. Then you could have a think about what other key points on the network may see high wire temperatures in a future heatwave. The main difficulty I can see with that is that long main lines without junctions can use mostly maximum-length wire runs, and shortening all those would be costly. 

So is this still a serious issue? Well, Network Rail have been saying this about the problem, which suggests exceeding the temperature range of tensioners isn't common:

Modern overhead lines, which are used on the majority of Britain’s rail network, are much less affected by hot weather. They have auto-tension systems with balance weights or springs that adjust to different temperatures. But older overhead lines have fixed tension and are more vulnerable.

How we minimise delays caused by overheated power lines

We do this by:

• Adjusting the height and tension of our older overhead power lines in summer to help prevent sagging.
• Introducing temporary speed restrictions to minimise the force on the overhead power lines. Speed restrictions reduce the risk of damage and keep services running but they can cause delays. We have to balance the inconvenience of delays against the risk of the greater disruption that would be caused if we need to fully close the line.
• Replacing old overhead lines with modern, more resilient auto-tension power lines.

What was a surprise there was that there is any fixed wire without tensioners outside sidings and depots. I could only think of Tyne and Wear Metro (1500 V DC^▸ (Direct Current)), which isn't NR^» (Network Rail - home page)'s track except perhaps the bit that's shared. And maybe the fringes of Glasgow Suburban? But not on main lines, you'd hope.

Perhaps surprisingly, SNCF^▸ (Societe Nationale des Chemins de fer Francais - French National Railways) have always struggled in this area, and drooping caténaires are still part of their PR^▸ (Public Relations) message in hot weather. And that's despite having time to do something about it - I recall hearing of a big programme of uprating tensioners in France (though I can't now find a reference for that).

These are drop weights, and there are several ways of refitting them for a longer travel on the catenary side. I suspect the main problem is with the 1500 V DC  lines, which are heaver and presumably suffer more from traction current heating. And they are concentrated in the hot and sunny south. But even so, you'd have thought that was a fixable problem by now.

[Electric train]

Of the two main heat effects, OLE^▸ (Overhead Line Equipment, more often "OHLE") sag is the more tractable. In principle, temperature range is just a  parameter fed into the design process, and if you make it a bit bigger you just get a slightly different set of design rules. The obvious free parameter you can change is the maximum wire run length: on those Series 1 figures, reducing that from 1500 m to 1400 m would allow about 5 degrees more temperature range.

Tensioners with a greater adjustment length might work in some cases, but that increases the along-track movement of the wires. All the things bolted to the wires - registration arms in particular - must be able to cope with this extra movement. I suspect the registration arms would not allow much more than 1 m of movement. For the same increase from 74 to 79 K, a 1 m adjustment has to go up by 65 mm.

As a practical response to the current situation, you could look at any places where loss of tension has happened and work out why. If it's a set-up issue, sort it; if it's a place where the wires get very hot for whatever reason and the wire run is long, split that one into two shorter ones. Then you could have a think about what other key points on the network may see high wire temperatures in a future heatwave. The main difficulty I can see with that is that long main lines without junctions can use mostly maximum-length wire runs, and shortening all those would be costly. 

So is this still a serious issue? Well, Network Rail have been saying this about the problem, which suggests exceeding the temperature range of tensioners isn't common:

Modern overhead lines, which are used on the majority of Britain’s rail network, are much less affected by hot weather. They have auto-tension systems with balance weights or springs that adjust to different temperatures. But older overhead lines have fixed tension and are more vulnerable.

How we minimise delays caused by overheated power lines

We do this by:

• Adjusting the height and tension of our older overhead power lines in summer to help prevent sagging.
• Introducing temporary speed restrictions to minimise the force on the overhead power lines. Speed restrictions reduce the risk of damage and keep services running but they can cause delays. We have to balance the inconvenience of delays against the risk of the greater disruption that would be caused if we need to fully close the line.
• Replacing old overhead lines with modern, more resilient auto-tension power lines.

What was a surprise there was that there is any fixed wire without tensioners outside sidings and depots. I could only think of Tyne and Wear Metro (1500 V DC^▸ (Direct Current)), which isn't NR^» (Network Rail - home page)'s track except perhaps the bit that's shared. And maybe the fringes of Glasgow Suburban? But not on main lines, you'd hope.

Perhaps surprisingly, SNCF^▸ (Societe Nationale des Chemins de fer Francais - French National Railways) have always struggled in this area, and drooping caténaires are still part of their PR^▸ (Public Relations) message in hot weather. And that's despite having time to do something about it - I recall hearing of a big programme of uprating tensioners in France (though I can't now find a reference for that).

These are drop weights, and there are several ways of refitting them for a longer travel on the catenary side. I suspect the main problem is with the 1500 V DC  lines, which are heaver and presumably suffer more from traction current heating. And they are concentrated in the hot and sunny south. But even so, you'd have thought that was a fixable problem by now.

There are a number of factors to be considered with increasing the tension on OLE. 
The registration on curved track will need to be enhanced to accommodate the pull / push of forces.
The actual contact wire alloy may need to be changed
The dynamic uplift will be reduced thereby increasing the wear on the pan and may even put it outside the spec of the pan uplift force
Increased tension on the OLE can lead to more OLE component failures if they have not been changed to accommodate the increase in forces.

There may be some fixed equipment about, if I recall correctly there is a max speed limit of 70 mph on plan line and as low as 40 on radiuses

DC 1500V contact wire is much heavier gauge almost twice that of 25kV

[BBM]

What was a surprise there was that there is any fixed wire without tensioners outside sidings and depots.

Ardwick to Hadfield and Glossop via Guide Bridge still has fixed wire catenary without tensioners which was installed in the 1950s as part of the Woodhead electrification project. The insulators were replaced in the 1980s when the OHLE was changed from 1500V DC^▸ (Direct Current) to to 25kV AC but no other upgrade work was carried out. Last Monday as a precaution the EMUs^▸ (Electric Multiple Unit) were replaced by DMUs^▸ (Diesel Multiple Unit) but on Tuesday the service had be stopped altogether due to a sagging contact wire at Gorton.

[stuving]

While looking for helpful material about track thermal expansion and its problems, I came across an RAIB^▸ (Rail Accident Investigation Branch) accident report which is more useful than all the rest together! This is report 11/2016, "Derailment of a freight train near Langworth, Lincolnshire, 30 June 2015". It's so useful because the accident was a derailment caused by buckled track, and also because RAIB do try very hard to explain technical issues clearly as well as accurately.

The train contained 22 empty diesel fuel tank wagons, of which nine derailed and four rolled over. If they had been full, you'd probably remember it now - as it is you probably didn't even notice at the time.

Most of the report is relevant, but the section of "background information" starting on page 19 has a broader application. However, it isn't a complete primer on "how to manage track to avoid buckling" - it leaves out a lot that is not relevant to this accident. For example, it mentions "adjustment switches" (aka scarf joints) because there are some in the other track, but does not say how they are used in general.