Passenger Trains > Heat restrictions today in DC area

Heat restrictions have been imposed in the Washington DC area, as announced by MARC
and VRE.  While it's not that hot (low 80s) a spread of over 40°F between low and high temps
has probably triggered the restrictions.

GenePoon Wrote:
-------------------------------------------------------
> Heat restrictions have been imposed in the
> Washington DC area, as announced by MARC
> and VRE.  While it's not that hot (low 80s) a
> spread of over 40°F between low and high temps
> has probably triggered the restrictions.

Gene as you mentioned it's not so much how hot/cold the temp is ... it's the extreme fluctuation between the high/low temps where the steel doesn't have time to adjust to expand or contract respectively and comprising the integrity of the rail finding the weakest point in the steel altho most so called "broken rail" incidents happen at rail joints and field welds with thermite field welds being the weakest type of welding process ... that's why most class Is prefer the electric butt welding process over thermite field welding due to lessening the chance of any type of minute air pockets in the welds ... after the welds are made they should be ultra sound field tested within a day or 2 to ensure integrity

when steel is made the cooling process process is controlled to establish a high strength quality ... take notice to steel rail and you'll see CC stamped next to the info on the web of the rail to show the rail was Control Cooled

Posted from Android



Edited 1 time(s). Last edit at 05/04/15 10:26 by Out_Of_Service.

Wow!  At first I thought maybe it was getting hot in the halls of Congress or something.

John
 

Out_Of_Service Wrote:
-------------------------------------------------------
> Gene as you mentioned it's not so much how
> hot/cold the temp is ... it's the extreme
> fluctuation between the high/low temps where the
> steel doesn't have time to adjust to expand or
> contract respectively and comprising the integrity
> of the rail finding the weakest point in the steel

Now, now.  The CWR is not supposed to expand or contract in temperature fluctuations.  Its supposed to change stress states.  Stress = Strain * Young's Modulus.  Its only expanding or contracting if there is a problem with the stress state changing or inadequate ballast to retain position of the track.

abyler Wrote:
-------------------------------------------------------
> Out_Of_Service Wrote:
> --------------------------------------------------
> -----
> > Gene as you mentioned it's not so much how
> > hot/cold the temp is ... it's the extreme
> > fluctuation between the high/low temps where
> the
> > steel doesn't have time to adjust to expand or
> > contract respectively and comprising the
> integrity
> > of the rail finding the weakest point in the
> steel
>
> Now, now.  The CWR is not supposed to expand or
> contract in temperature fluctuations.  Its
> supposed to change stress states.  Stress =
> Strain * Young's Modulus.  Its only expanding or
> contracting if there is a problem with the stress
> state changing or inadequate ballast to retain
> position of the track

the CWR properly anchored and stabilized expands vertically through the rail base, rail web and rail head unless a weak point in the roadbed arises which at that point the rail finds the point of least resistance

Posted from Android

Out_Of_Service Wrote:
-------------------------------------------------------
> abyler Wrote:
> --------------------------------------------------
> -----
> > Out_Of_Service Wrote:
> >
> --------------------------------------------------
>
> > -----
> > > Gene as you mentioned it's not so much how
> > > hot/cold the temp is ... it's the extreme
> > > fluctuation between the high/low temps where
> > the
> > > steel doesn't have time to adjust to expand
> or
> > > contract respectively and comprising the
> > integrity
> > > of the rail finding the weakest point in the
> > steel
> >
> > Now, now.  The CWR is not supposed to expand
> or
> > contract in temperature fluctuations.  Its
> > supposed to change stress states.  Stress =
> > Strain * Young's Modulus.  Its only expanding
> or
> > contracting if there is a problem with the
> stress
> > state changing or inadequate ballast to retain
> > position of the track
>
> the CWR properly anchored and stabilized expands
> vertically through the rail base, rail web and
> rail head unless a weak point in the roadbed
> arises which at that point the rail finds the
> point of least resistance

The verical expansion or contraction can't relieve the axial strain caused by the rail wanting to get longer but being unable to do so, which is the key factor.