Extreme Cold effects on Track and Wheels?

[Randy Stahl]

Tis the season for shelled wheels.

[jeffhergert]

tree68

 

 

466lex

In all of the report (unless I missed it) there was no suggestion that the air temperature of -1⁰ F may have been a contributing factor.

 

 

It may have been, but all too often these flaws are found to have existed long before they finally failed.  Sometimes something helps them fail, sometimes they just give up on their own.

I've seen information about incidents indicating that rust was found within the point where a part failed, indicating that it had been that way for a while.

 

Whenever a train breaks a knuckle, the report form asks the percentage of old break.  That is, how much rust is showing at the failure point.

Jeff

[tree68]

466lex

In all of the report (unless I missed it) there was no suggestion that the air temperature of -1⁰ F may have been a contributing factor.

It may have been, but all too often these flaws are found to have existed long before they finally failed.  Sometimes something helps them fail, sometimes they just give up on their own.

I've seen information about incidents indicating that rust was found within the point where a part failed, indicating that it had been that way for a while.

[blue streak 1]

Extreme temperature changes can affect many materials.  When train cars can travel from desert temps of 114 to -40 to -50 one has to wonder.

What may be more significant is anything built with two or more materials.  Different co-efficients of expansion rates of different materials that are connected together will always cause problems.

An unkown number of thermal cycles will also eventually weaken any material  ( each material will have different rates ).

[466lex]

I just again looked at the NTSB report on the BNSF’s Casselton, ND CBR accident in 2013, in which a covered hopper in a unit grain derailed into the path of the oil train.  A broken axle under the hopper was cited as the cause.  The report goes into great detail about the axle:

 

“Investigators found an axle assembly in the wreckage that was broken in half. On-scene examination suggested that the axle had fractured at a void along the longitudinal center axis.16 The axle was sent to the National Transportation Safety Board (NTSB) materials laboratory for further examination.”

 

In all of the report (unless I missed it) there was no suggestion that the air temperature of -1⁰ F may have been a contributing factor.  Perhaps the engineers and metallurgists concluded that it wasn’t, but it seems at least a comment to that effect would have been in order.

 

Not that there is any direct analogy, the infamous role of ambient temperature in the tragic Challenger space shuttle loss comes to my mind.

 

https://www.ntsb.gov/investigations/AccidentReports/Reports/RAB1701.pdf

[mudchicken]

... and it's hard to get the rest of the tribe to come out and play the rail changeout game in those low temperature conditions. Pandora's box ain't got nuttin' on opening up a grade crossing in adverse conditions.

[Paul_D_North_Jr]

It's complicated.  See:

https://www.physicsforums.com/threads/at-what-temperature-range-can-brittle-fracture-be-expected-in-low-carbon-steels.519090/ 

http://www.spartaengineering.com/effects-of-low-temperature-on-performance-of-steel-equipment/ 

Using the -20 deg. C mentioned in those articles = 32 deg F - 20 x 1.8 deg. = -4 deg. F.  So any steel near that temperature may be at risk.  However, note all the technical details regarding alloys and grain structure, etc. 

Plus, what mudchicken said corresponds with my experience.  At cold temps. it doesn't take much of an impact . . .  

- PDN.  

[mudchicken]

All those little nicks and voids (occlusions) become hypersensitive in the cold. It does not much for a nicked rail in a crossing* to break from all the abuse from highway traffic. The nicks from the broken wheel above will have the roadmaster and track supervisor watching carefully for months and the D-Car can't show up fast enough to see if anything is "growing"...

 

Nicks from lowboys, trailer jackstands and low-hanging dunnage are a constant problem. (The rail nicks are basically loaded guns picking their time and place to go off.)

[BaltACD]

It does.  Broken wheels (not necessarily caused by the cold) when traversing track in bitter cold and break rail, potentially every revolution, when a sharp edge of the broken wheel strikes the rail like a very heavy chisel.

CSX rules when I retired required trains that left 2 track occupancy lights lit to be safely stopped and inspected for potential broken wheels.  In one case I recall, a train did find a broken wheel and MofW personnel found 12 breaks in the 8 miles of the track circuit that the train had left on.  Trains that only leave one circuit on continue without any special inspections.

[CandOforprogress2]

Would it make tracks and wheels more brittle?