Around the DC area whenever the temps head toward the mid 90s CSX starts slowing down all the MARC trains which share the tracks because of the danger of sun kinks in the tracks. Now I understand what they are and what causes them, but I am confused as to why NS, VRE and Amtrack never announce service delays on their tracks. Does this happen all over their system, or just where there is a significant fluctuation in temperatures from summer to winter. You never hear about track being made unsafe in the winters because the stress of the steel contracting pulling the ends of sections apart. Does that happen?
CSX puts out heat orders on all of there subdivisions when the temperatures is over a certain point. I belive that the order is given when the temperature reaches 85 degrees.
…Sure must be enough of a threat to issue the heat orders over a certain temp. With so many years of using CWR…it sure seems unusual to me, why some sort of design has not been incorporated to limit that threat. I know of the Pandrol clips…good ballast…clips at each side of ties, and so on…which must control most of the problem.
I have no idea what that might be, but surely in 40 or 50 years, someone could have figured out a cost effective way of doing it.
Why does CSX have this problem when UP, BNSF, and other lines that run through the desert don’t. Desert temperatures can vary from freezing at night to 120-130 degrees in the afternoon. Rail temperatures probably exceed that.
…Only a thought…I’d say the co’s running in desert heat do lay track…{install new rail}, at the upper bracket of the heat range it works in. So it is well “stretched” when layed.
Of course the eastern co’s such as CSX run in temps. as low as 20 degrees below “0” and perhaps their rail is put down lower in the heat bracket and then when we get unusual high temps there, there is a threat. Just my thought on the subject.
Obviously, there are folks here MUCH more qualified than I to address this, but I can say that times that I’ve been out fanning in bitter cold, we’ve often been skunked by broken rails shutting down service. I’m sure there are a myriad of circumstances that contribute to it, but extended bitter cold is surely one of them.
Heat and cold present alternate stresses up the track structure. Of the two, cold is the potentially least dangerous. When the track structure is stressed by cold, the track ‘shrinks’ until the weakest point is found, normally as a train passes over it, an the rail will break or a rail joint will break. In 99.99% of the cases, the train continues on and a track circuit remains illumated on the dispatchers model board which then results and signal and roadway personnel being dispatched to find the cause of the track circuit. While the track circuit remains on, trains will continue to operate into the affected track at restricted speed (No faster than 15MPH beind able to stop within 1/2 the range of vision).
Heat however, is more dangerous in that the stresses play out in an uncontrolled adjustment to the track alignment that normally does not cause a track circuit to be illuminated, thus trains can operate into a track structure that has a sun kink at unrestricted speed.
While neither condition is desired, both are realities that must be dealt with. As a practical reality. Track areas that have had broken rails during the winter are more prone to have sun kniks in the summer as the rail sections that get installed to repair the broken rail, are rarely if ever installed at a ‘normalized’ temperature that is equivalent to whatever temperature the welded rail was initally laid at. The ‘fix rail’ will normally be installed at the ambient temperature and will thus have more expansion potential than rail laid at the normalized temperatures of 90 to 100 degrees as is supposed to occur in initial welded rail installations.
Maybe it’s just your selective way of looking at it. A UP train had a large derailment on BNSF’s Transcon last week due to a sun kink. So yes, it does happen to others besides just CSX.