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Point rails panited white.

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tim_lathe

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I have a massive interest in railways and always have. I am also an engineer, both mechanical, electrical and electronic.

I would like to know, on my daily journey to work (Colchester Town to Chelmsford), just why the rails on some sets of points (those around Witham specifically) have had the webs and foot of the rails painted white, but only on the points.

Obviously such paint treatment involved a human being with a pot of paint and a brush and was therefore quite costly. The only conclusion I can come to is that either those rails suffer some sort of cracking or are already cracked, and those who inspect them wish to see the progress of such cracking easily, or that the rails suffer some sort of shuffle on the chairs (expected on points at high speed), and once again this can be seen by the rust dust produced.

Alternatively, one assumes that these rails are identified for replacement.

In either case, the fact that a Norwich to London class 90 set (1P11) goes through there at approx. 8am (while I am sitting on 9th coach of 1A95 in P1) at about 60 MPH is worrying if the points are no good.

We'll get to the subject of wheelflats later - another point I have.

I'd hope (and don't know) that facing points on a 100 MPH main line are inspected daily.

Maybe someone more skilled in permanent way inspection and repairs can advise me.
 
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WatcherZero

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Its to reflect light so they don't get as hot and the metal expand in summer.
 

tim_lathe

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Sorry, I do not believe that. The white painted sections are only 100' (if that) long and seem to be welded to normal rail (in the main direction) by some sort of butt weld that incorporates a 1" long section of steel that remains bright. Therefore, the expansion of 100' of rail will in no way counteract the expansion of god knows how much is welded to it.

Not that solar heating is that intense, and the white rails seem to be covered in brake / wheel dust and are more like brown anyway.
 

Shaw S Hunter

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Disbelieve all you like. The fact is there are many places on the network that have been identified as (literal) hotspots and receive the white paint treatment. It's not always to protect against expansion of long welded rail, it's also used to protect point blade detection, particularly at junctions where the points are reversed frequently.
 

tim_lathe

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Considering the published expansion of average steel is 15um per metre per Kelvin, then that is not very much. If it is so critical, then from an engineers point of view then why is it allowed to become mucky from wheel dust, significantly reducing the solar heating coefficient of the rail.

In any case, CWR etc. has been in this country for 40 years and not until this year have I seen white rails.

I would accept that it seems to be the case that the point frogs in these locations are integral castings welded to the running rails, as opposed to being bolted.

In any case it is not good engineering practice, the ironwork should be immune to all reasonably expected thermal variations.
--- old post above --- --- new post below ---
And furthermore, if this is applied where point reverse is frequent, why are not the up main to up loop points at witham and the down main to plat. 1 at Colchester so treated? Also the pointwork on the Colchester to Colchester town triangle (Eastgates Jn, Colne Jn and Hythe Jn) so treated?
 

Shaw S Hunter

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Is that assuming normal air density and light/heat path and not assuming reflection off a mirrored or glass surface?

Whilst the top surface of a well used rail may well have a surface approaching mirror quality the much larger sides do not. The usual rust build up can only act to absorb heat, not reflect it. So the white paint will provide some mitigation.

Considering the published expansion of average steel is 15um per metre per Kelvin, then that is not very much. If it is so critical, then from an engineers point of view then why is it allowed to become mucky from wheel dust, significantly reducing the solar heating coefficient of the rail.

In my lifetime in this country I have known measured air temperature variations between -29 and +38, ie a range of 67K. Add in another 20K for heat absorption and you start to approach an amount that can make a difference. And I wonder how much that expansion figure is affected by the particular composition of the steel used for rails.

In any case, CWR etc. has been in this country for 40 years and not until this year have I seen white rails.

That may be so but white painted rails have been around for a while, I can vouch for one location going back 7 years and I couldn't possibly claim to know about the whole network!

And furthermore, if this is applied where point reverse is frequent, why are not the up main to up loop points at witham and the down main to plat. 1 at Colchester so treated? Also the pointwork on the Colchester to Colchester town triangle (Eastgates Jn, Colne Jn and Hythe Jn) so treated?

Clearly some locations are more susceptible to solar gain than others. The location referred to above is plain line with no pointwork. And yet it very quickly receives a heat based speed restriction during spells of hot weather.
 

DarloRich

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Sorry, I do not believe that. The white painted sections are only 100' (if that) long and seem to be welded to normal rail (in the main direction) by some sort of butt weld that incorporates a 1" long section of steel that remains bright. Therefore, the expansion of 100' of rail will in no way counteract the expansion of god knows how much is welded to it.

Not that solar heating is that intense, and the white rails seem to be covered in brake / wheel dust and are more like brown anyway.

disbelieve what you like. The rails are painted white to reflect some sunlight and reduce heat related problems in the formation. Does the stressing work on the rail explain why thermal expansion is such a problem?
 

theageofthetra

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It does beg the question though why do our points and junctions need it with such a relatively mild climate? There were several places I went to this year in China where winter temps can reach -20c & summer +40c but didn't see white rails. I can understand rail being designed for say the tropics where it is always hot but how do for example the junctions around Beijing station cope given the huge temp variation, v heavy weight (massive loading gauge) & high traffic density?
 

Deepgreen

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Whilst the top surface of a well used rail may well have a surface approaching mirror quality the much larger sides do not. The usual rust build up can only act to absorb heat, not reflect it. So the white paint will provide some mitigation.



In my lifetime in this country I have known measured air temperature variations between -29 and +38, ie a range of 67K. Add in another 20K for heat absorption and you start to approach an amount that can make a difference. And I wonder how much that expansion figure is affected by the particular composition of the steel used for rails.



That may be so but white painted rails have been around for a while, I can vouch for one location going back 7 years and I couldn't possibly claim to know about the whole network!



Clearly some locations are more susceptible to solar gain than others. The location referred to above is plain line with no pointwork. And yet it very quickly receives a heat based speed restriction during spells of hot weather.

The absolute air temperature recorded range for the UK is -27.2C to 38.5C. Actual rail temperatures may exceed both those extremes (especially the upper one), and broken rails are a often symptom of very low temperatures as rails are generally stressed when laid to the equivalent of 27C. The reason point blades/rails are sometimes painted is because their function makes them very sensitive to temperature-induced expansion, in terms of locking and providing a secure 'throw'. Longer stretches of rail have expansion joints built in to absorb some of the effects of expansion to minimise buckling.

See also the recent thread on Glasgow Central's white-painted points.
 

Phil.

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Considering the published expansion of average steel is 15um per metre per Kelvin, then that is not very much. If it is so critical, then from an engineers point of view then why is it allowed to become mucky from wheel dust, significantly reducing the solar heating coefficient of the rail.

In any case, CWR etc. has been in this country for 40 years and not until this year have I seen white rails.

I would accept that it seems to be the case that the point frogs in these locations are integral castings welded to the running rails, as opposed to being bolted.

In any case it is not good engineering practice, the ironwork should be immune to all reasonably expected thermal variations.
--- old post above --- --- new post below ---
And furthermore, if this is applied where point reverse is frequent, why are not the up main to up loop points at witham and the down main to plat. 1 at Colchester so treated? Also the pointwork on the Colchester to Colchester town triangle (Eastgates Jn, Colne Jn and Hythe Jn) so treated?

OK, OK I'll come clean. We just paint the rails to give one of our thousands of rail engineers something to do instead of leaning on a shovel at lineside. We'd like to thin them out a bit but those beastly unions who really are in charge won't let us so we are vastly over manned. We use white paint because Dulux had a surfeit of the stuff as their unions insisted on no redundancies when they went to auto paint production in an effort to reduce their wage bill. Some others of our "workforce" are detailed to travel on trains to soil the seats and scatter litter about to keep the train cleaners in a job as passengers are so tidy these days the trains virtually self-clean themselves. Ever notice all that litter on the track? Yep, that's another department that does that.
Running railways, it's not all about trains y'know.

Now, instead of trolling about how you know better than a system that has over 150 years of experience in running railways - more in fact than any other country - just accept things are done in a certain way because that's the way to do it and it works.
 

DarloRich

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OK, OK I'll come clean. We just paint the rails to give one of our thousands of rail engineers something to do instead of leaning on a shovel at lineside. We'd like to thin them out a bit but those beastly unions who really are in charge won't let us so we are vastly over manned. We use white paint because Dulux had a surfeit of the stuff as their unions insisted on no redundancies when they went to auto paint production in an effort to reduce their wage bill. Some others of our "workforce" are detailed to travel on trains to soil the seats and scatter litter about to keep the train cleaners in a job as passengers are so tidy these days the trains virtually self-clean themselves. Ever notice all that litter on the track? Yep, that's another department that does that.
Running railways, it's not all about trains y'know.

Dont be silly: The paint isn't cheap! It is marked up by at least 1059% as the tax player is the one doing the buying.

Now, instead of trolling about how you know better than a system that has over 150 years of experience in running railways - more in fact than any other country - just accept things are done in a certain way because that's the way to do it and it works.

I think it is a practical and affordable, if less than optimum, way to mitigate a particular problem.
 

AM9

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... Now, instead of trolling about how you know better than a system that has over 150 years of experience in running railways - more in fact than any other country - just accept things are done in a certain way because that's the way to do it and it works.

Leave him alone. He's doing well for a new member. Despite several replies by established members to his question, he still poo-poos their answers. Not bad in just 3 posts and 16 hours!
 

ComUtoR

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Dont be silly: The paint isn't cheap! It is marked up by at least 1059% as the tax player is the one doing the buying.

It's because of the EU that paint must meet 255 EU laws. Its great for UK business as it makes the standard white #ffffff easily exported to eurozone. If we leave the EU it will make Magnolia 11x more expensive as we will have higher tax duty and that Germany will refuse to trade with the UK and we have to send some P-Way guys over to stick it in the back of a van under the tarpaulin.

and it works

When I started there was always the typical summer points buckling problems. Ever since they started painting them white its lessened considerably. In fact, one year they forgot and the points buckled !
 

Bigfoot

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Leave him alone. He's doing well for a new member. Despite several replies by established members to his question, he still poo-poos their answers. Not bad in just 3 posts and 16 hours!

Three replies of very much - I'm an engineer and I know best! Although I have actually no experience in the field that I am talking about I overrule anyone who has knowledge of the situation.
 

Elecman

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He must have attended the Whitby school of not knowing when to quit. He certainly is no Engineer.
 

455driver

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So you join a forum to ask a question, the question is answered and you won't accept the (correct) answer, priceless.

Please join my ignore list. :lol:

He reminds me of that clart who asked what a brake force runner was and when we replied it was to provide brake force he didn't believe us either.
 
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edwin_m

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Longer stretches of rail have expansion joints built in to absorb some of the effects of expansion to minimise buckling.

Modern track, including switches and crossings, is designed to withstand the thermal stresses across the expected temperature range without the need for expansion joints. They are provided only when the track on one side is of an older design that couldn't cope with these stresses.
 

carriageline

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I love this place at times!! Silly know it alls, that actually know as much as a tea cup. I love how he thinks it's one massive conspiracy. Some people know more than you, get over it...


Sent from my iPhone using Tapatalk
 

Trog

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Modern track, including switches and crossings, is designed to withstand the thermal stresses across the expected temperature range without the need for expansion joints. They are provided only when the track on one side is of an older design that couldn't cope with these stresses.

Nearly but not quite true there are a few things that still need protecting with adjustment switches, and at tight radii you can not use CWR and are forced to use jointed even if in modern materials. Some structures also need adjustment switches both where an expansion joint in the structure could effect the stress in the rail, and to prevent traction forces being passed through the track into a weak structure below.
 

Bald Rick

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It is generally used on unstrengthened point work, which is stuff that is not stressed. Whilst it may be welded, it is not continuously welded, and therefore not stressed to cope with thermal expansion. Having the white paint helps reduce the thermal expansion and thus the chance of switch blades being out of tolerance, and thus the points failing. It's a particular issue for switch diamonds.

It's been done for at least 15 years to my knowledge.
 
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