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(My Fox DC)   Subway tracks get inspected because of extreme heat. One day later, Metro train derails. Good job inspectors   (myfoxdc.com) divider line 3
    More: Fail, metro, extreme temperatures, underground trains  
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5035 clicks; posted to Main » on 13 Jul 2012 at 12:36 AM (1 year ago)   |  Favorite    |   share:  Share on Twitter share via Email Share on Facebook   more»



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2012-07-13 01:25:09 AM
1 votes:
The engineering term for it is a "thermal misalignment". Modern railroad mainline is almost all CWR or continuous welded rail. Back in the day rail came in standard length sections that was bolted together, thus providing expansion/contraction points when the weather got hot or cold. All those joints require a lot of maintenance though, which is why the jump to CWR was made. Unfortunately you lose all those points of expansion/contraction, so you have to combat it in other ways.
The normal methodology is to lay the CWR at a certain temperature, causing the rail to expand when it's being installed, and locked in with rail anchors or some other form of fastening technology. The track structure can resist compressive forces much easier than expansive, and everything should be good.
What happens in instances like this could be attributed to maintenance, like cutting in a rail plug during the winter and not taking the steps to adjust the rail's temp, or it could just be rail movement over a long period of time, especially around areas such as switches or crossings (or the concrete section as shown in the picture) as they can act like an anchor point. It could also be attributed to poor components of the track structure.
Regardless, this isn't necessarily a rare instance, especially in areas experiencing higher than normal temperatures.

/used to be a gandy dancer
//bonus points if you know what that is w/out googling the term
2012-07-13 12:50:08 AM
1 votes:
Steel melts at 2600o.

Wake up, sheeple.
2012-07-12 10:36:07 PM
1 votes:

Skywolf Philosopher: If extreme heat bends the tracks, what about some kind of sensor that snaps when the track bends? Would that work?


Don't really know much about railroads per se, just speaking from a general engineering/system design standpoint, but there are a lot of things that will work from sensors to expansion joints and probably even changing the alloys used for the tracks. But all of them cost time and lots and lots of money. Giant infrastructure systems are designed around a set of parameters (including temp range), and if those parameters start consistently running outside the initial assumptions, you have a big expensive problem on your hands.

Just one of the many highly expensive problems we'll have on our hands if global temps continue to rise.
 
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