Life expired track

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najaB

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Still this phrase a few times - what is the limiting factor on track life: is it profile change due to wear, or fracture risk due to fatigue?
 
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coppercapped

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Still this phrase a few times - what is the limiting factor on track life: is it profile change due to wear, or fracture risk due to fatigue?

Do you mean 'track' or 'rails'? Your question looks as if it means only the rails, but track includes the sub-base, ballast, sleepers and so on as well as the rails.
 

najaB

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Do you mean 'track' or 'rails'? Your question looks as if it means only the rails, but track includes the sub-base, ballast, sleepers and so on as well as the rails.
Well, the phrase as used is 'life expired track' - I'm making the assumption that re-ballasting would be covered by the term 'track maintenance'.

All things being equal, and assuming that there's no deficiency in construction, which is likely to be life-expired first: rail or sleepers?
 

Trog

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All things being equal, and assuming that there's no deficiency in construction, which is likely to be life-expired first: rail or sleepers?

It depends on the traffic and the curvature.

Roughly speaking the sleepers will last twice as long as the ballast, provided there is not a problem with the formation below the ballast. On moderate to lightly used lines the rails and sleepers will last about the same amount of time. On heavily used lines or where there is tight curvature the rails will wear out before the sleepers.
 

Bald Rick

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Without being too flippant, life expired track is simply when some or all of the track system is beyond economic repair, and it is easier to replace.

There are 5 main components (top first)

Rails
Fastenings
Sleepers (bearers in point work)
Ballast
Formation including drainage


Rails can last a long time - I've pulled out rail over 100 years old. Equally, some needs renewing every few years, particularly on rails with high tonnage, high speed and high cant deficinecy (eg WCML and ECML). Rerailing is classed as a renewal once you go above a certain length (can't remember how long).

Replacing fastenings is a maintenance job. However some fastenings are more prone to failure than others (eg Pan 8) and are considered life expired, and the whole track system will be replaced at the same time.

Sleepers - if the odd one breaks that's a maintenance job. Timber sleepers, particularly softwood, will normally rot more quickly than a concrete sleeper will decay. However some types of concrete sleeper are known to decay more quickly basically due to either their reinforcement wires corroding, and/or the concrete mix being less than ideal. Again, this will happen more quickly on high tonnage / high speed routes.

Ballast loses its angularity over time, partly through small movement under the passage of trains, and partly through tamping. Tiny pieces break off, creating fines (essentially sand) which clog the ballast causing it to lose its drainage properties. Rounded ballast is also not so good at locking sleepers into place, so more minor movement occurs and then the problem escalates. There are some locations around the country where limestone ballast was used; this is less hard than granite and will become, a problem much more quickly.

Formation life depends on the geology underneath. Decent rock or sand formation is great, clay and peat / fen is not. Clay is well know for pumping up through the ballast causing a 'wet spot' which causes all sorts of geometry and track defects. Digging out a wet spot on a wet Tuesday night in February is (in my experience) the hardest job on the railway. Any replacement of ballast and formation more than an occasional wet spot is a renewal.

Putting all the above together, life expired track can be any or all of the above, but usually means rail, sleepers, ballast and fastenings together, with formation / drainage done in about 20% of cases.

However once you have to renew the ballast, it is almost always more efficient in whole life terms to renew the sleepers and rails as well, as the cost of the new materials is a relatively small proportion of the job. In fact it is usually actually cheaper in initial cost terms to replace rails and sleepers with new than save the old ones. The process of dismantling and temporarily storing the old stuff takes longer and needs more plant and manpower than it does to simply cut the old track into 20 metre panels, chuck it on a train, and get it away. If the old sleepers have any life in them they can be reused elsewhere; rail will typically be scrapped unless it is in in very good condition. (The scrap value is generally more than the cost of unloading and reloading the rail at a depot, plus doing the necessary ultrasonic checks to ensure the rail is fit for reuse).
 
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najaB

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Without being too flippant, life expired track is simply when some or all of the track system is beyond economic repair, and it is easier to replace...
Thanks to you as well. I hope nobody minded the 'stupid question' for the sake of some complete explanations of a term that gets used a lot.
 

HMS Ark Royal

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Thanks to you as well. I hope nobody minded the 'stupid question' for the sake of some complete explanations of a term that gets used a lot.

The only stupid questions are those that are never asked...
 

Xenophon PCDGS

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Sleepers - if the odd one breaks that's a maintenance job. Timber sleepers, particularly softwood, will normally rot more quickly than a concrete sleeper will decay.

I know that hardwood sleepers were much in use in the 19th century on certain lines and a particular type of Australian timber called Jarrah (Eucalyptus Marginata) was also very popular as use for sleepers with those early railway companies (Many of these redundant Jarrah ones are now readily available for purchase for use in gardening projects, in particular).
 

ian959

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I know that hardwood sleepers were much in use in the 19th century on certain lines and a particular type of Australian timber called Jarrah (Eucalyptus Marginata) was also very popular as use for sleepers with those early railway companies (Many of these redundant Jarrah ones are now readily available for purchase for use in gardening projects, in particular).

Still in use today in some places on the West Australian network, where Eucalyptus marginata hails from.
 

Altnabreac

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Without being too flippant, life expired track is simply when some or all of the track system is beyond economic repair, and it is easier to replace.

There are 5 main components (top first)

Rails
Fastenings
Sleepers (bearers in point work)
Ballast
Formation including drainage


Rails can last a long time - I've pulled out rail over 100 years old. Equally, some needs renewing every few years, particularly on rails with high tonnage, high speed and high cant deficinecy (eg WCML and ECML). Rerailing is classed as a renewal once you go above a certain length (can't remember how long).

Replacing fastenings is a maintenance job. However some fastenings are more prone to failure than others (eg Pan 8) and are considered life expired, and the whole track system will be replaced at the same time.

Sleepers - if the odd one breaks that's a maintenance job. Timber sleepers, particularly softwood, will normally rot more quickly than a concrete sleeper will decay. However some types of concrete sleeper are known to decay more quickly basically due to either their reinforcement wires corroding, and/or the concrete mix being less than ideal. Again, this will happen more quickly on high tonnage / high speed routes.

Ballast loses its angularity over time, partly through small movement under the passage of trains, and partly through tamping. Tiny pieces break off, creating fines (essentially sand) which clog the ballast causing it to lose its drainage properties. Rounded ballast is also not so good at locking sleepers into place, so more minor movement occurs and then the problem escalates. There are some locations around the country where limestone ballast was used; this is less hard than granite and will become, a problem much more quickly.

Formation life depends on the geology underneath. Decent rock or sand formation is great, clay and peat / fen is not. Clay is well know for pumping up through the ballast causing a 'wet spot' which causes all sorts of geometry and track defects. Digging out a wet spot on a wet Tuesday night in February is (in my experience) the hardest job on the railway. Any replacement of ballast and formation more than an occasional wet spot is a renewal.

Putting all the above together, life expired track can be any or all of the above, but usually means rail, sleepers, ballast and fastenings together, with formation / drainage done in about 20% of cases.

However once you have to renew the ballast, it is almost always more efficient in whole life terms to renew the sleepers and rails as well, as the cost of the new materials is a relatively small proportion of the job. In fact it is usually actually cheaper in initial cost terms to replace rails and sleepers with new than save the old ones. The process of dismantling and temporarily storing the old stuff takes longer and needs more plant and manpower than it does to simply cut the old track into 20 metre panels, chuck it on a train, and get it away. If the old sleepers have any life in them they can be reused elsewhere; rail will typically be scrapped unless it is in in very good condition. (The scrap value is generally more than the cost of unloading and reloading the rail at a depot, plus doing the necessary ultrasonic checks to ensure the rail is fit for reuse).

Excellent post. Informative and well informed. Thanks for continuing to post such useful information.
 

Bald Rick

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If I may tag along to this thread, how is rounded (worn) ballast collected and disposed of?

You dig it up. It then goes by train to a reprocessing plant, cleaned (I think) and is sold for reuse as something similar to MOT type 1 as a base layer for construction. Ironically, much ends up under new roads.

Used ballast is technically contaminated waste, as it will contain several decades of dropped oil, hydraulic fluid, and, errrr, effluent.


--- old post above --- --- new post below ---
I know that hardwood sleepers were much in use in the 19th century on certain lines and a particular type of Australian timber called Jarrah (Eucalyptus Marginata) was also very popular as use for sleepers with those early railway companies (Many of these redundant Jarrah ones are now readily available for purchase for use in gardening projects, in particular).

Indeed, and I've seen Jarrah near Perth. Remarkable trees.

New hardwood sleepers are still used here, but only in special circumstances.
--- old post above --- --- new post below ---
Thanks to you as well. I hope nobody minded the 'stupid question' for the sake of some complete explanations of a term that gets used a lot.

It's actually a very good question.

Track renewal is quite a complex subject. It seems simple, being basically rock, concrete and metal - I mean how hard can it be (as various senior managers and directors have said). Very hard is the answer.

I tell all engineering graduates that pass through on their trip around the company that they should do a spell in track renewals. It is hard work, very unsocial hours, potentially significant consequences if you get anything wrong, but anyone who hasn't done it thinks it's just a case of laying out bits of rock, concrete and metal.
 
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DarloRich

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I know that hardwood sleepers were much in use in the 19th century on certain lines and a particular type of Australian timber called Jarrah (Eucalyptus Marginata) was also very popular as use for sleepers with those early railway companies (Many of these redundant Jarrah ones are now readily available for purchase for use in gardening projects, in particular).

hardwood sleepers and bearers are still used - although they aren't Jarrah anymore.
 

Joseph_Locke

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If I may tag along to this thread, how is rounded (worn) ballast collected and disposed of?

The railway recycles a lot of it using a large mobile chainsaw / screening machine called a ballast cleaner. This sieves out the rubbish and puts the usable ballast back, all at about 300m of track per hour (with the track still there); see this youtube video.

As Bald Rick says, if it's too far gone (full of slurry, etc.) then you take the track up and load the ballast into rail wagons using diggers.
 

najaB

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As Bald Rick says, if it's too far gone (full of slurry, etc.) then you take the track up and load the ballast into rail wagons using diggers.
Or, for big jobs, using the High-Output Ballast Cleaner (trivia: the longest train formation regularly seen on the UK network).
[youtube]UgsHycXWOU0[/youtube]
 

Bald Rick

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The HOBC is good where the ballast isn't completely clogged and there's no (or very few) wet spots; the used ballast would clog up the machine.

Also, until very recently, it was no good on third rail routes as the con rail got in the way. However that has now been sorted, and it has been out south of Horsham over the last few weeks.

Nevertheless, traditional methods can be remarkably productive - renewing c1500 metres of rail sleepers and ballast in a 52 hour weekend possession is relatively routine. This is generally the more efficient method on secondary routes where the financial implications of weekend possessions are lower.


One thing I meant to say earlier. The Highways Agency has learnt a thing or two from the railways recently. Until around 10 years ago, motorway resurfacing was typically done by installing lane closures and a contra flow, which would be in place for a couple of months on a 5-10 mile stretch.

Now, they throw plant and labour at it overnight in 7-8 hour lane closures, and will resurface a few hundred lane metres per night. Very similar production process to the high output kit, and much more friendly to traffic flow.
 

snowball

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One thing I meant to say earlier. The Highways Agency has learnt a thing or two from the railways recently. Until around 10 years ago, motorway resurfacing was typically done by installing lane closures and a contra flow, which would be in place for a couple of months on a 5-10 mile stretch.

Now, they throw plant and labour at it overnight in 7-8 hour lane closures, and will resurface a few hundred lane metres per night. Very similar production process to the high output kit, and much more friendly to traffic flow.
However, to compensate for that, they've found another way of achieving long-running lane closures: coversion to "smart" motorways.
 

DarloRich

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One thing I meant to say earlier. The Highways Agency has learnt a thing or two from the railways recently. Until around 10 years ago, motorway resurfacing was typically done by installing lane closures and a contra flow, which would be in place for a couple of months on a 5-10 mile stretch.

Now, they throw plant and labour at it overnight in 7-8 hour lane closures, and will resurface a few hundred lane metres per night. Very similar production process to the high output kit, and much more friendly to traffic flow.

Railways? Something to be copied? Surely not! What do they know about anything. Backward, old fashioned and militant ;)

Or, for big jobs, using the High-Output Ballast Cleaner

Not if the formation is really wet. When the ballast gets like porridge the machine struggles.
 

edwin_m

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However, to compensate for that, they've found another way of achieving long-running lane closures: coversion to "smart" motorways.

But they normally manage to keep the same number of lanes by narrowing them and reducing the speed, avoiding the lane closures and contraflows that used to cause huge tailbacks a few years ago. Shame the railway can't do that.

I do agree some of the road works seem unnecessarily long in distance and/or time. There was a 20-mile one on the M1 last year and it was only slightly shorter a month or so back when I last travelled through. Avoiding lane closures ought to allow them to re-open the sections where no work is taking place.
 

Joseph_Locke

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But they normally manage to keep the same number of lanes by narrowing them and reducing the speed, avoiding the lane closures and contraflows that used to cause huge tailbacks a few years ago. Shame the railway can't do that.

How does a railway achieve narrow lanes, pray tell? There is only (normally) 300mm between trains on adjacent lines.

Granted that reducing the speed would allow you to review the track interval, but the lower limit is 100mm irrespective of speed.

We often have contraflows, but the legislation that your elected representatives have enacted means the railway has to deploy significant safety measures which generally make doing it less than cost effective.

We had a contraflow through Farnworth, but it was there for so long it made sense. The "good old days" of single line working on a Sunday afternoon with a pilotman seems not to be widely favoured these days but I spent 8 years working like that (and being careful which side of the Tamper I got out of ...)
 

edwin_m

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How does a railway achieve narrow lanes, pray tell? There is only (normally) 300mm between trains on adjacent lines.

Granted that reducing the speed would allow you to review the track interval, but the lower limit is 100mm irrespective of speed.

We often have contraflows, but the legislation that your elected representatives have enacted means the railway has to deploy significant safety measures which generally make doing it less than cost effective.

We had a contraflow through Farnworth, but it was there for so long it made sense. The "good old days" of single line working on a Sunday afternoon with a pilotman seems not to be widely favoured these days but I spent 8 years working like that (and being careful which side of the Tamper I got out of ...)

It wasn't a serious suggestion... perhaps it needed a smiley or two as well as "Shame the railway can't do that"?
 

Why

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What about this for needing renewal ? Durrington on Sea, third rail - corroded, holes everywhere in around 30ft ...how old would that conductor rail be?
 

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D Foster

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Couple of tiny points -

We used to call taking the whole lot out down to the planet a "Deep Dig". Since then they seem to usually use the opportunity to build the new formation in several very "technical" layers and to include textile layers. I would guess that modern replacement track should last a lot longer.
The difference between modern CWR and designed systems and the early Victorian 30foot rails laid on the best that could be found (fairly) locally must be immense.

The other factor is that weekend deep-digs and even ballast cleaning jobs also involved "bussing" the passenger service around the job. That was always an immense source of "fun" :D

:p
 
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