NTSB report on East Palestine accident

[Euclid]

Here is some discussion that is critical of how the timeline for the rising bearing temperature trend has been covered by the NTSB report:

 

https://www.trainorders.com/discussion/read.php?2,5882596

[Euclid]

Say you have a freight train in dynamic braking, and you suddenly experience a U.D.E., thus triggering an automatic air brake “Emergency” application, which will stop the train as quickly as possible.

Does the dynamic brake control system recognize the U.D.E. and respond by automatically stopping dynamic braking at the moment the U.D.E. occurs?

 

[jeffhergert]

Euclid

Say you have a freight train in dynamic braking, and you suddenly experience a U.D.E., thus triggering an automatic air brake “Emergency” application, which will stop the train as quickly as possible.

Does the dynamic brake control system recognize the U.D.E. and respond by automatically stopping dynamic braking at the moment the U.D.E. occurs?

 

 

Depends. A UDE will open the PCS which cuts power or dynamics. Newer engines and those retrofitted will maintain dynamics when the PCS opens.

I don't know if this feature is an option or standard on new engines. I know we have this feature on most, if not all road engines now.

Jeff

[Euclid]

jeffhergert

 

 

Euclid

Say you have a freight train in dynamic braking, and you suddenly experience a U.D.E., thus triggering an automatic air brake “Emergency” application, which will stop the train as quickly as possible.

Does the dynamic brake control system recognize the U.D.E. and respond by automatically stopping dynamic braking at the moment the U.D.E. occurs?

 

 

 

 

 

Depends. A UDE will open the PCS which cuts power or dynamics. Newer engines and those retrofitted will maintain dynamics when the PCS opens.

I don't know if this feature is an option or standard on new engines. I know we have this feature on most, if not all road engines now.

Jeff

 

What was the reasoning for having the PCS open to cut out dynamic braking in the event of a U.D.E., when that was in the design?  And what is the reasoning for having newer engines maintain dynamics in the event of a U.D.E.?

 

What would be the benefit of applying dynamic braking during a U.D.E.?  It seems like it might be problematic.

[jeffhergert]

The reason they want dynamics to keep working when the PCS opens, and other things can cause the PCS to open, is for trains operating in heavy grade areas. Mountains. 

The PCS doesn't know if it's open due to a train separation, air hose bursting, or if the engineer (or conductor) just placed the train in emergency. Going down a heavy grade you want to maintain all the braking effort possible. I believe it was some of the runaways that brought about changes.

Jeff

[BaltACD]

Euclid

 

jeffhergert 

Euclid

 

Say you have a freight train in dynamic braking, and you suddenly experience a U.D.E., thus triggering an automatic air brake “Emergency” application, which will stop the train as quickly as possible.

Does the dynamic brake control system recognize the U.D.E. and respond by automatically stopping dynamic braking at the moment the U.D.E. occurs? 

Depends. A UDE will open the PCS which cuts power or dynamics. Newer engines and those retrofitted will maintain dynamics when the PCS opens.

I don't know if this feature is an option or standard on new engines. I know we have this feature on most, if not all road engines now.

Jeff 

What was the reasoning for having the PCS open to cut out dynamic braking in the event of a U.D.E., when that was in the design?  And what is the reasoning for having newer engines maintain dynamics in the event of a U.D.E.?

 

What would be the benefit of applying dynamic braking during a U.D.E.?  It seems like it might be problematic.

One element of the reasoning is to prevent a secondary impact between the two parts of a train that has broken in two because of a broken knuckle or pulled out drawbar.  Wether the reasoning is appropriate or not is open to discussion.  Releasing Dynamics when the UDE trips the PCS would leave BOTH parts of the train with only emergency air braking as the primary and only braking - theoretically allowing both parts of the train to have similar stopping distances.

If the UDE trips the PCS but the Dynamics aren't released, theoretically the head end will stop BEFORE the rear end of the train.  If the rear end runs into the stopped head end of the train there is a distinct possibility of a derailment at the impact point.

The above applies to when a train has head end power only.  With DPU's in the power make up - all bets are off.  Jeff Hergert would be the authority on that aspect of train dynamics.

Any UDE interjects wildly acting in-train forces, even on level tangent track; when those force begin acting on a train in graded terriory - all bets are off, especially when it happens on descending grades where a high level of curvature has been built to get the grade to manageable levels for ascending the grade.

[Euclid]

I understand Jeff’s point that locomotive with dynamic brakes have been built in two different versions that affect how they will respond to a UDE that occurs while dynamic brakes are braking against a moving train.  I also understand the reason for the version that does not cut out dynamic braking in the advent of a UDE or any other Emergency application of air brakes.

 

In territory with heavy grades, I can see the advantage of the control system allowing applied dynamic braking to continue in the advent of a U.D.E.  Basically, it would be the situation where the more braking available, the better. 

 

Regarding these two different versions of locomotive dynamic brake operation:  In a case where dynamic braking is applied, one version will cut out dynamic braking in the advent of a UDE; and the other version will not cut out dynamic braking in the advent of a UDE.

 

In the case of the version that does not cut out dynamic braking, I assume that the engineer is able to manually cut out or otherwise operate dynamic braking controls in the same manner as usual.  Is my assumption correct?    

 

Considering relatively flat track where an engineer is using dynamic braking to decelerate the train in preparation to stop the train.  Let’s say there are 100 cars between the head end power and the first trailing DPU.  In this example, buff force caused by dynamic braking would accumulate collectively among all of the 100 cars trailing the engine.  This is because these trailing cars have no braking applied, so their inertia presses them ahead against the resistance of the dynamic braking only applied to the head end power. 

 

Then, in continuing this example of operation, suddenly a UDE occurs, originating near the head end. This sudden Emergency application runs in a wave toward the rear of the train while building its accumulating pressure of buff force against the head end locomotives.

 

In this case; both the pressure of the ongoing dynamic braking plus the pressure wave of the UDE air brake application; are combining to build the highest buff force pressure nearest the head end of the train.  For some increment of time, both sources of buff force are likely to be at their maximum, and adding to each other. 

 

To reduce the danger of this high buff force, I would expect that it would be advisable to release dynamic braking upon realizing that the train has experienced a UDE, and is making a full Emergency application to the entire train.   

 

Otherwise, if the buff force rises high enough, it will buckle the train in a horizontal plane.  The first two cars to buckle will fold together in a jackknifing action.  The next two cars will follow with the same jackknifing action. When the train finally stops, most of the cars will be laid out roughly side by side. 

[BaltACD]

Once a wheel hits the ground in a derailment, all predictability of what the ultimate outcome will be is gone. 

[Euclid]

BaltACD

Once a wheel hits the ground in a derailment, all predictability of what the ultimate outcome will be is gone. 

 

Yes, you never know what will happen when a wheel leaves the rail. Among other things, it depends on speed, length and makekup of train, grades, curves, terrain, slack, DPU interaction, and train handling.   

 

What I consider the strangest result of a wheel derailing at speed, is when a wheel derails and runs on the ground for maybe 500 feet, and then it gets back on the rail and runs fine. 

 

In East Palestine, one car went on the ground and ran on the ties for 1400 feet.  Other than one wheelset running on the ties, it stayed true to the line of track well enough to keep the air hoses connected.  But for some reason, the equilibrium ended.  If it would have lasted long enough to get 40 mph off of the train, it would have saved maybe a billion dollars.  

 

[BaltACD]

Train becoming uncoupled -

https://www.youtube.com/watch?v=S1wytAllGkY

 

[Euclid]

Here is an NS train at Cresson, PA that is tipping over the rail as it goes; an unusual example of what I call “Derailed-Dragging.”  In this case, it is as if the train is passing over a switch which switches the running surface of the rails from their tops to their sides. 

 

Other variations of these freakish events can have trains running on the ground for many, miles without ever parting the trainline and jackknifing cars into a pileup.  They often tear out grade crossings and keep right on going.

 

A more common variation is when a train puts one wheelset on the ties.  They will cause track damage to some extent. 

  

https://www.youtube.com/watch?v=5rFlCgco2nM