Overmod tree68 jeffhergert They can have other defects where they don't work properly, but as someone has observed - you always have the "Big Hole" as a last resort. I gradually opened a back-up hose once - to the point it was fully open and exhausting air from the brake line. Because I had done so gradually, the brakes never dumped, and there was now no way to make them do so. So this is shaping up as an attended version of Lac Megantic...
tree68 jeffhergert They can have other defects where they don't work properly, but as someone has observed - you always have the "Big Hole" as a last resort. I gradually opened a back-up hose once - to the point it was fully open and exhausting air from the brake line. Because I had done so gradually, the brakes never dumped, and there was now no way to make them do so.
jeffhergert They can have other defects where they don't work properly, but as someone has observed - you always have the "Big Hole" as a last resort.
I gradually opened a back-up hose once - to the point it was fully open and exhausting air from the brake line. Because I had done so gradually, the brakes never dumped, and there was now no way to make them do so.
So this is shaping up as an attended version of Lac Megantic...
The procedure they are describing is known as venting a train, and as long as the reduction rate exceeds 3 PSI per minute it will result in a full service brake application on the train, and a brake pipe pressure of 0 PSI.
The purpose of that procedure is to not put the train in emergency in order to save the air in the cars' emergency reservoirs, and to prevent emergency vent valves on the cars from sticking open (a real problem in cold weather).
At Lac-Megantic the auxiliary reservoir air leaked out through the brake pipe due to the very slow reduction rate and no air went to the cars' brake cylinders, which is the exact opposite result of the venting procedure Zug and Larry described.
Cycle braking too many times can indeed achieve the same end result as Lac-Megantic, but so far all we have here is rumours, no hard facts yet.
A unintentional release or blockage of the brake pipe could easily cause the same end result, if the Engineer did not catch it right away.
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jeffhergert It looks like the area where it happened is on a mostly 1.5 % grade. One report I was shown by a coworker said the train picked up cars (I think in Laramie WY) and was 12000 tons. One of the engines involved was a SD70m, but unknown when I was shown this info last week was if it was leading. They have a mechanical brake valve, either a 26L or the desk top equivalent, and lately some have been having pressure maintaining issues. They can have other defects where they don't work properly, but as someone has observed - you always have the "big Hole" as a last resort. Assuming the brake pressure hasn't dropped below about 45 or 50 psi. Below that pressure, emergency may not be transmitted through the brake pipe. Passenger equipment will automatically dump when pressure drops below 20 psi as a fail safe last resort. Freight equipment doesn't have that feature. Jeff
It looks like the area where it happened is on a mostly 1.5 % grade. One report I was shown by a coworker said the train picked up cars (I think in Laramie WY) and was 12000 tons.
One of the engines involved was a SD70m, but unknown when I was shown this info last week was if it was leading. They have a mechanical brake valve, either a 26L or the desk top equivalent, and lately some have been having pressure maintaining issues. They can have other defects where they don't work properly, but as someone has observed - you always have the "big Hole" as a last resort. Assuming the brake pressure hasn't dropped below about 45 or 50 psi. Below that pressure, emergency may not be transmitted through the brake pipe. Passenger equipment will automatically dump when pressure drops below 20 psi as a fail safe last resort. Freight equipment doesn't have that feature.
Jeff
Do the automatic brake valves on UP power have "freight" and "passenger" positions, or do you only have "in" and "out"?
In my experience changing the automatic mode from "freight" to "passenger" (with the automatic released of course) usually makes the unit pressure maintain properly. Nearly all of CN's units with 26 and 30 type brake valves (except the ex-Oakway SD60's) have all 3 positions.
We discussed this problem in another thread not so long ago, and I think it was Big Jim who said that a leaky gasket somewhere inside the control stand is the most common cause of that problem.
FRA signal worker stated it was a runaway. DS notified other trains to stop and get off. That is all known to date.
OvermodThe similar proximate cause was, undeniably, the leaking off of the brake air
The cause of the Lac Megantic crash was a failure to set sufficient handbrakes. The air brakes had nothing to do with the cause of the accident.
Plus we don't know if the air "leaked off". It could be insufficient supply, it could be too much was used, it could be a failure of the brake valve, it could be a lot of different things that have nothing to do with a leak. For example, if the engineer used the brakes too often without allowing them to recharge, that's not a "leak", that is an intentional use of the brakes.
There are things that point to an air brake problem, but we don't know any of the details about what the crew did and and what the train did.
Dave H. Painted side goes up. My website : wnbranch.com
dehusmanWouldn't say that at all. Lac Megantic was a failure to properly secure a standing train. While we don't know what the cause was, we know that it wasn't that.
The similar proximate cause was, undeniably, the leaking off of the brake air, almost precisely at the sort of rate recounted in earlier posts in this thread, resulting in the automatic brake failing to apply and hold or slow the train when the independent no longer held it. Whether the leak was through a defective valve or an air turbine, or whether there were insufficient handbrakes applied to hold the train with the airbrakes released, are not particularly germane to this discussion.
There is one thing, though. Balt said
BaltACDImmediately, we have cast guilt on the following train's crew.
It seems to me that, regardless of a 'cause' releasing the air from the car reservoirs, there would have been an indication on the head-end air gauges. Is that an erroneous conclusion, and (if so) what combination of service faults or failures would produce normal-appearing gauge readings with substantially no application pressure available at the wheel cylinders?
I'll be interested to see what the NTSB says regarding the state of the brake system.
OvermodSo this is shaping up as an attended version of Lac Megantic...
Wouldn't say that at all. Lac Megantic was a failure to properly secure a standing train. While we don't know what the cause was, we know that it wasn't that. Completely different sets of rules and procedures and possible causes.
SD70DudeHe may have been thinking of Trip Optimizer, which DOES operate the train, to varying degrees of success. TO is so good that it is not allowed to use the air brakes, and requires the Engineer to take over in numerous other situations too. But between TO and PTC the eventual goal is to run autonomous trains. A couple of Class I's have publicly stated that.
Yeah, that what I was referring to. Please pardon my D'oh moment.
Probably better to say that this is one possibility among the many already discussed. Running a signal is likely the higher percentage choice.
Larry Resident Microferroequinologist (at least at my house) Everyone goes home; Safety begins with you My Opinion. Standard Disclaimers Apply. No Expiration Date Come ride the rails with me! There's one thing about humility - the moment you think you've got it, you've lost it...
tree68I gradually opened a back-up hose once - to the point it was fully open and exhausting air from the brake line. Because I had done so gradually, the brakes never dumped, and there was now no way to make them do so.
Used to do it all the time to cars attached to ground air.
The opinions expressed here represent my own and not those of my employer, any other railroad, company, or person.
jeffhergert They can have other defects where they don't work properly, but as someone has observed - you always have the "big Hole" as a last resort.
Thanks Jeff. I can see how that would lead to questioning the brake response.
EuclidI was just asking those who mentioned hearing of a possible braking problem if there was any reason given for suspecting a possible braking problem.
Think about who mentioned it.
BaltACD NDG - Thanks for this link - not of this incident but illustrative https://www.liveleak.com/view?t=sNzK_1539570515
NDG - Thanks for this link - not of this incident but illustrative
https://www.liveleak.com/view?t=sNzK_1539570515
You are welcome!
Thank You.
EuclidIs it nothing more than one possible conclusion simply because the train did not stop?
Give the man a cigar!
BaltACD Euclid Was the train descending a significant grade? Have there been many instances of peeing away the air on relatively flat trackage? With the comments about a possible brake problem, what has been the underlying basis for that piece of information? Is it nothing more than one possible conclusion simply because the train did not stop? Grades don't have to be significant for 10 - 12 - 15 -18K tons or more to do horrendous damage when the train runs away. Grade and tonnage build momentun - momentum that takes increasingly more braking power to bring back under control. That I am aware of, there has not been any published 'cause' for this incident.
Euclid Was the train descending a significant grade? Have there been many instances of peeing away the air on relatively flat trackage? With the comments about a possible brake problem, what has been the underlying basis for that piece of information? Is it nothing more than one possible conclusion simply because the train did not stop?
With the comments about a possible brake problem, what has been the underlying basis for that piece of information? Is it nothing more than one possible conclusion simply because the train did not stop?
Grades don't have to be significant for 10 - 12 - 15 -18K tons or more to do horrendous damage when the train runs away. Grade and tonnage build momentun - momentum that takes increasingly more braking power to bring back under control.
That I am aware of, there has not been any published 'cause' for this incident.
I realize that no cause has been published. I was just asking those who mentioned hearing of a possible braking problem if there was any reason given for suspecting a possible braking problem.
EuclidWas the train descending a significant grade? Have there been many instances of peeing away the air on relatively flat trackage? With the comments about a possible brake problem, what has been the underlying basis for that piece of information? Is it nothing more than one possible conclusion simply because the train did not stop?
Never too old to have a happy childhood!
Was the train descending a significant grade? Have there been many instances of peeing away the air on relatively flat trackage?
dehusman zardoz The ability of PTC to successfully operate a train shows just how much easier it is to run a train today compared to the time frame mentioned. PTC does not "operate the train." There is nothing in PTC that makes a train go, it is all about stop. PTC doesn't slow the train down for speed restrictions. Its not cruise control or a "self driving" feature. As long as the train is operated below the speed limit and within its authority, PTC takes no active role in the operation of the train. PTC is purely a penalty system.
zardoz The ability of PTC to successfully operate a train shows just how much easier it is to run a train today compared to the time frame mentioned.
PTC does not "operate the train." There is nothing in PTC that makes a train go, it is all about stop. PTC doesn't slow the train down for speed restrictions. Its not cruise control or a "self driving" feature. As long as the train is operated below the speed limit and within its authority, PTC takes no active role in the operation of the train. PTC is purely a penalty system.
He may have been thinking of Trip Optimizer, which DOES operate the train, to varying degrees of success.
TO is so good that it is not allowed to use the air brakes, and requires the Engineer to take over in numerous other situations too.
But between TO and PTC the eventual goal is to run autonomous trains. A couple of Class I's have publicly stated that.
zardozThe ability of PTC to successfully operate a train shows just how much easier it is to run a train today compared to the time frame mentioned.
David1005 There have been several run away trains over the years. One cause is repeated applications and releases of the brakes that works the auxilirary reservoir pressures down to the point where the train speed can not be comtrolled. This is probably considered an operating error. Another cause is a blocked brake pipe. This could be a closed angle cock, ice blockage, pinched air hose, etc. There is a variety of causes for this and investigation will have to determine exact cause. DPU locos would eliminate this possibility as it allows an emergency application mid train. UP lost control of a coal train years ago due to excess piston travel on truck mounted brake cylinders. I think it is unlikely this could happen again due to design changes. Since this train was a mixed consist a similar situation does not exist.
There have been several run away trains over the years. One cause is repeated applications and releases of the brakes that works the auxilirary reservoir pressures down to the point where the train speed can not be comtrolled. This is probably considered an operating error. Another cause is a blocked brake pipe. This could be a closed angle cock, ice blockage, pinched air hose, etc. There is a variety of causes for this and investigation will have to determine exact cause. DPU locos would eliminate this possibility as it allows an emergency application mid train. UP lost control of a coal train years ago due to excess piston travel on truck mounted brake cylinders. I think it is unlikely this could happen again due to design changes. Since this train was a mixed consist a similar situation does not exist.
charlie hebdoThe railroad safety record today vs 25 or 50 years ago is much better, let alone 100 years ago. Look at the statistics for facts, don't rely on anecdotal evidence to drw generalizations.
No doubt that safety is better today compared to 50+ years ago, although I'm doubtful regarding the 25-year figure. However, there was so much more to be concerned about (see above) for the railroaders of those days compared to today, and I'm not even considering the complexities of running steam locomotives.
The ability of PTC to successfully operate a train shows just how much easier it is to run a train today compared to the time frame mentioned. I'm not saying it is easy, I'm just saying it is easier.
And my observations come from not entirely 'anecdotal evidence', but also from first-hand experience.
zardozPerhaps it has something to do with the calibre of many of the new hires (in the offices, on the ground, and in the cab).
Or perhaps incidents didn't garner national/worldwide attention like they do in today's instant information age.
zardoz petitnj More reason to remove the crew from driving the train and only run when PTC like systems operate. And yet somehow for over 100 years we were able to operate trains and get them over the road, despite the lack of either proper equipment and/or management that knew the difference between a drawbar and a crowbar. AB brakes, brass journals, no dynamics, poor cab heaters, 39' jointed rail, 'flimsies' handed up to a train at track speed, no radio communication, 14-hour days....How did we ever do it without the miracle of PTC? Perhaps it has something to do with the calibre of many of the new hires (in the offices, on the ground, and in the cab).
petitnj More reason to remove the crew from driving the train and only run when PTC like systems operate.
And yet somehow for over 100 years we were able to operate trains and get them over the road, despite the lack of either proper equipment and/or management that knew the difference between a drawbar and a crowbar.
AB brakes, brass journals, no dynamics, poor cab heaters, 39' jointed rail, 'flimsies' handed up to a train at track speed, no radio communication, 14-hour days....How did we ever do it without the miracle of PTC?
Perhaps it has something to do with the calibre of many of the new hires (in the offices, on the ground, and in the cab).
Tragic as it is, this accident is an anomaly. The railroad safety record today vs 25 or 50 years ago is much better, let alone 100 years ago. Look at the statistics for facts, don't rely on anecdotal evidence to drw generalizations.
I had heard last week that there may have been a problem with the brakes, but no details on whether it was the train, the engines or the way they were operated.
petitnjMore reason to remove the crew from driving the train and only run when PTC like systems operate.
mvlandswEven if the electronic brake valve fails the emergency valve will still work. It is connected directly to the brake pipe - no electronics involved. However there could still be some other problem that prevents the brakes from working. Mark Vinski
Mark Vinski
If the trainline pressure has been 'pissed away' an emergency application will have little power if any.
Even if the electronic brake valve fails the emergency valve will still work. It is connected directly to the brake pipe - no electronics involved. However there could still be some other problem that prevents the brakes from working.
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