Since air in the train line acts like a fluid, might severe slack action cause a pressure wave to go thru the train line? A control valve that's prone to dynamite might see a momentary drop in air pressure and think an emergency application is being made.
I do know that slack action can have an effect on glad hands. Usually it's when the slack comes in. You'll see the EOT drop a few pounds then come back up or maybe see the air flow indicator show that more air is flowing back to the train for a few moments. Doesn't always initiate a UDE. Around my neck of the woods we call that problem having a "slip joint."
I did have a train once that when into emergency 4 times, everytime the slack came in. The problem car was towards the rear and the emergency stop tended to pull the slack out and the air would come back. The problem car was an autorack, the entire train was autoracks. It was a very cold morning before sunrise when we had the problems. Once the sun was up and it warmed just a bit, I experienced drops in pressure on the rear (both from the EOT reading and engine Air Flow gauge) but no UDE. I told the outbound engineer about it and that trying to keep it stretched seemed to help. (I still had it go on me one time with the head end in power and air set to keep it stretched.) When they left, I rolled the train by. 8 cars from the rear was a car with a new air hose. I had learned previously that long drawbar cars have a special air hose with the glad hand angled differently. (I found this out when we took a bunch out to a car man. We had been given those kind for long drawbar cars but he needed regular ones.) The new hose on this car was a regular one. It's not that they don't work, but that they don't always sit right. The slack coming in caused the hose to flex just enough to allow air to vent through the glad hands. Once it stretched out the glad hands seated enough to seal back up. I'm sure the cold contributed to the way the rubber seals were working too. The next time I saw the outbound engr, I asked if he had any problems. He said he hadn't, not even any excessive pressure loss on the rear end.
Jeff
Slack action could do that by jerking the glad hands on the air hoses so that one or more could pull apart or the couplers themselves lose integrity and pull apart (there could be a jumping up and down of the cars so that the couplers seperate up and down; this is the reason for tight lock couplers, those with a "shelf" or ear at the bottom). In pull aparts we don't often think in terms of virticle motion but horizontally along the line or plane of the train. I wonder, too, that if a mile long train has a difference say of 100 feet from bunched to stretched and a quick jerk would cause that 100 feet not to have pressure changing the train line pressure and setting brakes. I don't know how quickly a bunching or stretching would have to occur to have such a effect, but it might be very quick and violent enough to set the brakes..
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Henry,
What you say is true, but that is not the point of the few prededing posts. The point of those posts is slack run-out causing a pressure drop in the trainline, which then dynamites the brakes. Look at the reference in blue the fifth post above this one.
Actually, in looking at it again, I see that they don't specify run-out or run-in. They just refer to slack action causing brake pipe pressure to drop. I am mystified.
Can you explain how slack action can change the pressure in the trainline?
Isn't it not the slack running out but running in? I mean if the engineer dumps the air the brakes are set car by car, one at a time, from from to back even thought it is emergency and that it is quick....thus the front of the train stops short and the cars behind, depending on speed, grade, curvature, etc., will keep coming into the stopped or stopping cars with noplace to go but off the track either to the side or up or telescoped. Dumping the air does not mean all cars or the whole train loses air at once, it is still a front to back action, but much quicker than normal controlled applications. At least that seems to stand to reason.
Ed,
I hear what you are saying, but it still leaves me wondering. I agree that if slack run-out can cause a trainline pressure drop it must be due to the slight physical disturbance of the air hoses. I can’t imagine any other way that run-out could affect trainline pressure.
I know the gaskets can seal so poorly in cold weather that it can pose continuous leakage to the point of being a problem. So, I can see that in cold weather when the hoses and gaskets are stiff, run-out might turn the glad hands slightly and disrupt the gasket seal enough to cause a momentary leak. And it would only take one hose connection to trigger the emergency application of one car, and then continue on to the whole train.
I can see the hoses actually parting in problems with a cushioned drawbar mounting, as you mention, but the reference in the report seems to confine the issue to a pressure loss with no hose parting. It refers to a brake pipe pressure loss of up to 2 psi, so that must be just a momentary leakage rather than a complete drop associated with hose parting.
I am curious because I have heard about air hose gasket problems in cold weather many, many times, but never heard of slack alone causing a pressure drop in the trainline until reading that report.
Glad hand gaskets can leak, if there is break or tear, even worn spots on the gasket, the slack action or bunching up the cars can cause the glad hands to rotate just enough to allow these small gasket defects to leak badly.
And on some cars with cushioned under frames, the train line and air hose ride on a carrier rod, which allows the hoses to move with the draft gear, if the attachment hangs up, stretching the train or slack running out can cause the glad hands to separate.
All that holds glad hands together is gravity, the tension created by the hoses, (they are stiff and retain the slightly curved shape you see) and the internal air pressure helps hold the two parts together.
23 17 46 11
Paul_D_North_Jr Link to a Transport Safety Board of Canada report with an analysis and excellent discussion of this subject - see esp. the Appendices and the references: Report Number R00H0004 - http://66.203.200.38/eng/rapports-reports/rail/2000/r00h0004/r00h0004.asp
Link to a Transport Safety Board of Canada report with an analysis and excellent discussion of this subject - see esp. the Appendices and the references: Report Number R00H0004 - http://66.203.200.38/eng/rapports-reports/rail/2000/r00h0004/r00h0004.asp
Paul,
Thanks for posting those reports. The following is quoted from the first link in a discussion of how slack action can cause a pressure drop in the trainline sufficient to dynamite the train:
"1.17 UDE Research
Although most UDEs occurred subsequent to a service brake application, the report also concluded that slack action (draft and buff forces), accompanying or in the absence of a service brake application, may cause short-duration bpp reductions, leading to UDEs.
During this testing, it was demonstrated that severe slack action alone can produce sharp bpp reductions of up to 2 psi. Laboratory work also showed that control valves could respond to slack-induced bpp reductions and initiate a UDE."
What I would like to know is how it is possible for slack action to affect the trainline pressure.
I remember a derailment that occured in Birminham in May of 1963, and the cause was immediately known. The Southern's line into the Terminal Station crossed the main line of the L&N just east of the station, and the crossing was protected by a manual gate which was manned by the L&N. A Southern freight, bound for Northern Alabama, was approaching the crossing, and the L&N man suddenly threw the gate across the entrance to Terminal Station. The Southern engineer, instead of using the train brake, used the engine braks (I never heard why (I was passing through on the Peliican, bound for Bristol; Virginia). Even though the train was moving no faster than yard speed, several cars were derailed--blocking that entrance to the station. At that time there was track from North Birmingham to Woodlawn Jct., so the Pelican & the Seminole (on the CG) were not serious delayed.
Johnny
Another way would be by inference or deduction after ruling out the other usual possible causes. For example, if the track is in good condition, with no signs of internal defects where the rails broke, and recent Sperry and geometry car runs found no exceptions. Also, no equipment defects found such as broken wheels near the front of the wreck or old axle cracks, etc. Finally, some positive evidence of excessive train forces, such as a buckled car still on the tracks, or a pulled drawbar from a car at the front portion of the train, etc. There are 2-day professional courses on derailment investigations, and/ or people with years of practical experience, that go into this in far more detail.
- Paul North.
Bucyrus oltmanndI don't recall. In fact, they may have been train initiated emergencies I wonder how the crew would learn that a train-initiated emergency application caused a derailment. The only scenario I can think of would be if the crew found a broken air hose, broken trainline, or a break-in-two in one part of the train and a pileup in another part. That would be the "smoking gun."
oltmanndI don't recall. In fact, they may have been train initiated emergencies
I wonder how the crew would learn that a train-initiated emergency application caused a derailment. The only scenario I can think of would be if the crew found a broken air hose, broken trainline, or a break-in-two in one part of the train and a pileup in another part.
That would be the "smoking gun."
edblysard Do they always occur in response to a service application? Or do they sometimes occur spontaneously when no other braking event is occurring? If a train is found to contain a kicker, is there any way to determine which car in the train is the kicker? Is there ever an occurrance of one car with some type of brake valve defect that causes it to dump its air and dynamite the whole train when no service application is occurring? Not always, but that is the normal occurrence. Train lines leak, and sometimes, the pressure drop is just enough to set the kicker off, but most often the service reduction is the initial event. You can find a kicker, but it depends on where you are, how long the train is, how much time you have. While the engineer recharges the brakes, you walk to about the half-way point, and have him set the brakes. You listen, and can hear the “emergency” application and the air rush towards you; it will start from the kicker and work out both ways, towards the front and rear of the train. If the sound comes towards you from the rear of the train, the kicker is in the back half…start from scratch, have the engineer recharge the brakes while you make your way half way down the rear of the train, and start over…process of elimination will get you close enough to the kicker to finally hear it set off the brakes and you can isolate the car, which means you can sometime cut the brakes out on that car, but that also means you have to stop and set it out first chance, and on some roads it means you have to proceed to that point at restricted speed. If the kicker is very near the end of the train, and the situation permits, you can also close off the train line ahead of the last few cars and bleed the air off of them, but this means if your using a air powered EOT you have to put a flag on the rear end and run at restricted, no matter what you do, the dispatcher, who you should have already informed of your situation, will most likely set you off in a siding or instruct you to cut the car out at the next available place. If you trust your engineer enough, and the terrain permits, you just recharge the brakes and go, using the independent. On occasion, you never find the kicker, and because these are machines, the “problem” can disappear all on its own, it happens once, then the train behaves the rest of the run.
Or do they sometimes occur spontaneously when no other braking event is occurring?
If a train is found to contain a kicker, is there any way to determine which car in the train is the kicker?
Not always, but that is the normal occurrence.
Train lines leak, and sometimes, the pressure drop is just enough to set the kicker off, but most often the service reduction is the initial event.
You can find a kicker, but it depends on where you are, how long the train is, how much time you have.
While the engineer recharges the brakes, you walk to about the half-way point, and have him set the brakes.
You listen, and can hear the “emergency” application and the air rush towards you; it will start from the kicker and work out both ways, towards the front and rear of the train.
If the sound comes towards you from the rear of the train, the kicker is in the back half…start from scratch, have the engineer recharge the brakes while you make your way half way down the rear of the train, and start over…process of elimination will get you close enough to the kicker to finally hear it set off the brakes and you can isolate the car, which means you can sometime cut the brakes out on that car, but that also means you have to stop and set it out first chance, and on some roads it means you have to proceed to that point at restricted speed.
If the kicker is very near the end of the train, and the situation permits, you can also close off the train line ahead of the last few cars and bleed the air off of them, but this means if your using a air powered EOT you have to put a flag on the rear end and run at restricted, no matter what you do, the dispatcher, who you should have already informed of your situation, will most likely set you off in a siding or instruct you to cut the car out at the next available place.
If you trust your engineer enough, and the terrain permits, you just recharge the brakes and go, using the independent.
On occasion, you never find the kicker, and because these are machines, the “problem” can disappear all on its own, it happens once, then the train behaves the rest of the run.
Never too old to have a happy childhood!
Link to a Transport Safety Board of Canada report with an analysis and excellent discussion of this subject - see esp. the Appendices and the references:
Report Number R00H0004 - http://66.203.200.38/eng/rapports-reports/rail/2000/r00h0004/r00h0004.asp
Railway Investigation Report - Main Track Derailment - Ottawa Valley Railway/ RailAmerica, Inc.
Train 556-17 - Mile 1.88, North Bay Subdivision - Near Chalk River, Ontario - 20 June 2000
The following 2004 TSB report is on a 2001 derailment caused by excessive 'buff' forces after an emergency brake application was initiated by the train crew:
http://66.203.200.38/eng/rapports-reports/rail/2001/r01m0061/r01m0061.asp#a1
In particular, this photo of a upward-buckled tank car in that train testifies to the magnitude of those 'buff' forces - note that only 1 truck of that car derailed, though neither of the adjoining cars derailed:
http://66.203.200.38/eng/rapports-reports/rail/2001/r01m0061/r01m0061.asp#Photo_2
Finally, in that report are several references to other reports regarding train consist make-up and emergency braking related derailments.
Ed and Jeff,
Thanks for your explanations and information on this. What I did not realize until asking here is that a kicker is triggered by a service application. I had the impression that they were just a spontaneous event that would occur when running with brakes released.
Part of my curiosity about this stems from a short anecdote in Trains back in the 1990s called “God Is Not the Engineer.” I can’t recall all the details, but a trainmaster accused an engineer of bad train handling, and he told the trainmaster that it was an act of God because there was a kicker in the train. So he told the trainmaster that the problems with train handling was an act of God and God was not the engineer. The engineer even told the trainmaster which car was the kicker.
So I asked an engineer if there was any way to determine which car in a train was the kicker if there was one in the train. He told me that the only way he knew of would be if it were daytime, if there was fresh snow, and you were looking back along the train standing still, it might be possible to see a puff of snow at the kicker when it kicks.
But if a kicker will kick in reaction to a service reduction, then I can see how you could actually track it down if there was time by making the kicker kick and listening to the sound as Ed mentioned.
Another part of my curiosity was that article in Trains where a wreck inspector discovered the cause of a derailment to have been a kicker. But in that case, the wreck inspector made the discovery by digging into the heap of cars and discovering a kicker. Unless I am missing something, that would be absolutely impossible.
You know with all this talk about dynamiters, I'll probably have one in my train on my next trip. I haven't had one for quite a while, so I'm probably due for one anyway.
While any type of freight car can have a defective control valve that "kicks" or "dynamites," it seems like coal trains (loaded and empty) seem to be more prone to this. That would give creedence to the post about dirt and dust fouling the parts of the control valve.
Dynamiters also seem to come in two varieties. Those that go anytime you use the air and those that only go when you're going slow. About 20-25 mph or less. I have no idea why some only go at slow speeds.
One trick taught to me when you have a dynamiter is to move the automatic brake valve to minimum service for about a second and then back to release. Do this a couple of times before leaving it at minimum to start your brake application. Experts will say that has no effect, it's just coincidence that the dynamiter doesn't go when doing this. My experience is that the coincidence happens probably about 3/4 or better using that trick. My theory is that you get the air starting to "move" but not enough to trigger the dynamiter. The idea behind cutting out the air brakes on the first car was to "slow" the application to the train. The rules prohibit cutting out the air brakes on more than two consecutive cars because that could keep an emergency application from properly being transmitted.
While dynamiters are a pain in the backside, there usually is no urgency to locating which car(s) are doing it. You just deal with it the best you can. At lease when you have one you are expecting it. Not like when you're just rolling along and the air goes for no apparent reason.
The "transient phenomenon" challenge = occurs inconsistently sometimes, but not every time, and not predictably or in reliable accordance with any conditions that are easily discernable in the field. (Happens often with automobiles, too - ask any mechanic who deals mostly with the public . . . )
oltmanndA kicker by definition is a car that goes into emergency during a service application.
Is there ever an occurrance of one car with some type of brake valve defect that causes it to dump its air and dynamite the whole train when no service application is occurring?
Bucyrus Don, I can see Jeff’s point that an undesired emergency (UDE) is an oxymoron, at least some of the time. For instance if a train breaks in two, the air dynamites automatically on both halves. This was one of the primary advantages of the automatic air brake over straight air, or no air. So an emergency application resulting from a break-in-two is highly desired. However, in the case of a kicker, I agree with your observation that the emergency application associated with it is highly undesired. Therefore, to eliminate the oxymoron of the UDE in cases where it is not undesired, I would change the terminology from “undesired emergency” to “unintended emergency,” meaning that it happened without the engineer’s intention (or action). The word “unintended” would cover all emergency applications not made by the engineer (or other crewmember) regardless of their actual cause and desireability. I have a couple of key questions about kickers that I would like to clear up: Do they always occur in response to a service application? Or do they sometimes occur spontaneously when no other braking event is occurring? If a train is found to contain a kicker, is there any way to determine which car in the train is the kicker? *************** Your description of higher trainline pressure causing kickers in response to pressure waves is very intriguing. I gather that would mean that no one car in the train would be the pre-determined kicker. Instead, the pressure wave distributes the kicking potential to several cars, and one of them might kick. Then, as the wave distributes the potential another time, another car might respond by kicking. ***************
Don,
I can see Jeff’s point that an undesired emergency (UDE) is an oxymoron, at least some of the time. For instance if a train breaks in two, the air dynamites automatically on both halves. This was one of the primary advantages of the automatic air brake over straight air, or no air. So an emergency application resulting from a break-in-two is highly desired.
However, in the case of a kicker, I agree with your observation that the emergency application associated with it is highly undesired.
Therefore, to eliminate the oxymoron of the UDE in cases where it is not undesired, I would change the terminology from “undesired emergency” to “unintended emergency,” meaning that it happened without the engineer’s intention (or action). The word “unintended” would cover all emergency applications not made by the engineer (or other crewmember) regardless of their actual cause and desireability.
I have a couple of key questions about kickers that I would like to clear up:
Do they always occur in response to a service application?
***************
Your description of higher trainline pressure causing kickers in response to pressure waves is very intriguing. I gather that would mean that no one car in the train would be the pre-determined kicker. Instead, the pressure wave distributes the kicking potential to several cars, and one of them might kick. Then, as the wave distributes the potential another time, another car might respond by kicking.
A kicker by definition is a car that goes into emergency during a service application.
It is possible to determine where the car is by the timing of when the BP goes to zero a the head end vs. the rear end. I have heard that the EOTD equipment can do this although I don't know if any one is using it in practice this way.
The reflected pressure wave problem occurred on the long 89' flats that had a quick service valve portion on them - the what and how of this I don't recall. But, like you said, it could vary from car to car. All attempts to find "defective" brake valves failed. Finally, the AAR did some serious instrumented testing.
-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/)
I think everybody here is clear on the term "emergency" in this discussion. As you mention, it refers to a specific operating phase of the automatic air brake.
What you say about kickers is how I understand them too. But I would like to explore the behavior of kickers or dynamiters a little further. They have always been a bit of a mystery to me, and they present some questions that I have never gotten answers to.
I think there is a little confusion here in using the term "emergency". It is not the dictionary term but rather a railroad term describing the complete application of brakes or application of air at one time rather than controlled to a stop. Thus an emergency application can occur by the breaking of an air hose or line, uncoupling of cars, by anyone with access to the "emergency" valve on a freight or pasenger car or caboose, or by the engineer at his brakestand. Thus "emergency" in railroad terms means an quick and full application of brakes whether a dictionary definition of emergency exists or not.
Kickers or dynamiters I always thought were cars which had faulty brake release valves so that the least amount of air would trigger total release by the valve. DIrt, moisture, or other defect of the valve could cause it and sometimes one dumping will actually clean it so that it will react normally thereafter. It might also travel to the next or another valve.
jeffhergertAnymore, it seems like any emergency application, other than the engineer (or conductor) placing the train into emergency is lumped into the UDE category. Even if it's because the system does exactly what it's supposed to do when, for example, an air hose parts. Old heads used to say on trains with the long cars, cut out the first car's air brakes. That seemed to lessen the chance of a dynamiter. There are other tricks that are said to lessen a chance of a dynamiter, but the experts will say they don't work. It's just a coincidence when they do. Jeff
Old heads used to say on trains with the long cars, cut out the first car's air brakes. That seemed to lessen the chance of a dynamiter. There are other tricks that are said to lessen a chance of a dynamiter, but the experts will say they don't work. It's just a coincidence when they do.
Jeff,
Are you saying that the term UDE was originally intended to apply only to dynamiters?
What are some of those other tricks to lessen the chance of a dynamiter?
Anymore, it seems like any emergency application, other than the engineer (or conductor) placing the train into emergency is lumped into the UDE category. Even if it's because the system does exactly what it's supposed to do when, for example, an air hose parts.
Railway Age a few months back had an article about train handling technologies. I'd have to read it again, but it seems like it gave the impression that railroad attitudes are cooling towards ECP. I think part of the problem is what has already been stated, but I wonder if the railroad's preference for throttle modulation and dynamic braking before using the air brakes also plays into this.
jeffhergert Jeff PS. I think that undesired emegency (UDE) is an oxymoron. Sure, I know it is meant to differentiate between an engineer initiated emergency or one initiated from some other source. Still, who desires an emergency? If you need to use the big hole, things either aren't going right or are about to get real bad.
PS. I think that undesired emegency (UDE) is an oxymoron. Sure, I know it is meant to differentiate between an engineer initiated emergency or one initiated from some other source. Still, who desires an emergency? If you need to use the big hole, things either aren't going right or are about to get real bad.
steve14 Given track/train dynamics, an emergency brake application should not cause a derailment. I would expect there to have been some other condition that the braking forces found and made worse which could lead to a derailment. Will be interesting to see what the NTSB comes up with, in a year or so.
Given track/train dynamics, an emergency brake application should not cause a derailment. I would expect there to have been some other condition that the braking forces found and made worse which could lead to a derailment. Will be interesting to see what the NTSB comes up with, in a year or so.
Dispralan1 The engineer made several brake pipe reductions (aka brake applications), enough that it depleted both main and equalizing reservoirs below a safe level. When brakes were needed to reduce speed for a curve, not much happened, Even big-holing didn't get the train slowed sufficiently and the train exited the rails quickly for the inevitable pile up that resulted.
The engineer made several brake pipe reductions (aka brake applications), enough that it depleted both main and equalizing reservoirs below a safe level. When brakes were needed to reduce speed for a curve, not much happened, Even big-holing didn't get the train slowed sufficiently and the train exited the rails quickly for the inevitable pile up that resulted.
I think you mean the auxilary and emergency reservoirs on the cars. They are what operate the brakes on the cars. Too many applications and releases in a short time, where they don't have a chance to recharge, can deplete both reservoirs to the point there is little or no train braking available.
Whether an Emergency application, desired or not, will cause problems depends on conditions, too. Train make-up, where the train is (going up hill or downhill or thru a bunch of hogbacks, etc.) and for undesired applications where the dynamiter is in the train can influence whether or not you have problems. I'd agree that usually the worst outcome from a train going into emergency is a broken knuckle or drawbar. Although I don't doubt there have been derailments caused by emergency applications, I don't know of any personally other than what I've read about. Under the right (well, maybe wrong would be better) circumstances train (air brake) or dynamic braking can also cause problems up to and including derailments.
Someone mentioned about having to inspect the train after each emergency application. We don't have to inspect if certain condtions are met. Over the years the conditions have changes to the point that most trains no longer have to have a visual inspection. One exception is for key trains, those that have a prescribed number of loaded hazmat or just a single load of certain hazmat. They still need to be inspected.
" Here's one just the opposite, reviewed by the Interstate Commerce Commission several years ago. A train was running on main line trackage east of New Orleans. The engineer made several brake pipe reductions (aka brake applications), enough that it depleted both main and equalizing reservoirs below a safe level. When brakes were needed to reduce speed for a curve, not much happened, Even big-holing didn't get the train slowed sufficiently and the train exited the rails quickly for the inevitable pile up that resulted."
reckon a link to that would be useful?
Now the story about those two girls getting killed in Maryland posted above by Beaulieu sounds like the derailment might not have been induced by an emergency application, as was apparenly first thought. They are saying that the engineer did not dump the air to avoid hitting the girls. The girls were very close to the train while sitting on a bridge, but they were in the clear and not directely struck. They were killed by the pileup of cars. So they are looking for the cause of the derailment.
I wonder if either the NTSB and/ or FRA (or the TSB in Canada) in recent years - or the ICC in years gone by when it did the US rail accident investigations - ever investigated and reported in depth and detail on a derailment caused by this ? Such a report would be interesting to review, I expect.
Here's one just the opposite, reviewed by the Interstate Commerce Commission several years ago. A train was running on main line trackage east of New Orleans. The engineer made several brake pipe reductions (aka brake applications), enough that it depleted both main and equalizing reservoirs below a safe level. When brakes were needed to reduce speed for a curve, not much happened, Even big-holing didn't get the train slowed sufficiently and the train exited the rails quickly for the inevitable pile up that resulted.
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