M636C Euclid The main point of derailment detectors is to set the brakes as early as possible. The type that are completely mechanical and used with conventional air brakes, must dynamite the brakes if they detect a derailment. That has the potential to perturb the derailed-dragging car enough to cause a pileup, whereas, if left to drag without the “Emergency” application, the train may just stop for some other reason, resulting in the derailment being discovered. Last summer, a tank car load of acrylonitrile caught fire on the CSX in Tennessee. As it was later learned, that car had been derailed and dragging for NINE MILES. A derailment detector would have stopped the train as soon as the car derailed, and thus prevented the eventual fire that started from friction in the derailed truck. The benefit of combining derailment detectors with ECP is that there need not be an emergency application initiated upon derailment. A lighter application could be made in order to not upset the fragile equilibrium of a derailed-dragging car. Even if an “Emergency” application were initiated, it would apply simultaneously throughout the train, and thus reduce the risk of slack run-in perturbing the derailed-dragging car into causing a pileup. I'm certainly not opposed to derailment detectors, I've just never seen one.... Do many US freight cars carry these detectors? It would seem to be a good idea to equip new oil tank wagons with these devices as a standard fit, given the likelihood of avoiding some derailment accidents. Of course, the Lac Megantic disaster would not have been avoided by a derailment detector, since by the time the derailment occured, the unmanned train was travelling at a high speed and by definition was out of control. The combination of ECP braking and derailment detectors on all cars of a block oil train would have positive results in the case of rails breaking under the train or an axle bearing failure. This might be regarded as justifiable on block oil trains and other tank cars of hazardous substances. Non tank cars carrying Ammonium Nitrate, preferably not mixed with oil tank cars, might be worth fitting. But for general freight trains, unless all cars were fitted with derailment detectors, they will only work if a detector fitted car derails. A car with a detector could run for miles a few cars away from a derailed car without the actuator working. M636C
Euclid The main point of derailment detectors is to set the brakes as early as possible. The type that are completely mechanical and used with conventional air brakes, must dynamite the brakes if they detect a derailment. That has the potential to perturb the derailed-dragging car enough to cause a pileup, whereas, if left to drag without the “Emergency” application, the train may just stop for some other reason, resulting in the derailment being discovered. Last summer, a tank car load of acrylonitrile caught fire on the CSX in Tennessee. As it was later learned, that car had been derailed and dragging for NINE MILES. A derailment detector would have stopped the train as soon as the car derailed, and thus prevented the eventual fire that started from friction in the derailed truck. The benefit of combining derailment detectors with ECP is that there need not be an emergency application initiated upon derailment. A lighter application could be made in order to not upset the fragile equilibrium of a derailed-dragging car. Even if an “Emergency” application were initiated, it would apply simultaneously throughout the train, and thus reduce the risk of slack run-in perturbing the derailed-dragging car into causing a pileup.
I'm certainly not opposed to derailment detectors, I've just never seen one....
Do many US freight cars carry these detectors?
It would seem to be a good idea to equip new oil tank wagons with these devices as a standard fit, given the likelihood of avoiding some derailment accidents.
Of course, the Lac Megantic disaster would not have been avoided by a derailment detector, since by the time the derailment occured, the unmanned train was travelling at a high speed and by definition was out of control.
The combination of ECP braking and derailment detectors on all cars of a block oil train would have positive results in the case of rails breaking under the train or an axle bearing failure. This might be regarded as justifiable on block oil trains and other tank cars of hazardous substances. Non tank cars carrying Ammonium Nitrate, preferably not mixed with oil tank cars, might be worth fitting.
But for general freight trains, unless all cars were fitted with derailment detectors, they will only work if a detector fitted car derails. A car with a detector could run for miles a few cars away from a derailed car without the actuator working.
M636C
Posted by blue streak 1 on Friday, February 19, 2016 8:53 PM
Could it be that the only way to maintain a good electrical connection would be for the connection become part of the air hose connection ? Then a car knocker when hooking up the air hoses would have to spray contact cleaner on the electrical connection part. UGH ! !.
There actually is an electrical connector that would be analogous to the glad hand in that it would have to be "made" but would break easily. I'm using a small version of the connectors (the Anderson "PowerPole") for my ham radios. I'll let you look them up.
Assuming that appropriate stress relief could be arranged, I'd suspect they would work.
I'm only worried about a two conductor plug for supplying power to my radios. If more electrical conductors were needed, it could probably be arranged, although it may be possible to code the braking signal on top of the supply voltage.
Properly designed, changing out a cable wouldn't be any more difficult than changing out an air hose. They could easily be designed with appropriate metals to combat corrosion.
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...
tree68 There actually is an electrical connector that would be analogous to the glad hand in that it would have to be "made" but would break easily. I'm using a small version of the connectors (the Anderson "PowerPole") for my ham radios. I'll let you look them up.
Those type connections are used for connecting external batteries for starting cars in racing. Would have to be toally reengineered for a rail use and as they exist would experience a high level of wear, as well as weather problems over time.
Electrical connections and unattended disconnection of them sould like they have a high potential for recurring failure in the railroad world.
Never too old to have a happy childhood!
blue streak 1Could it be that the only way to maintain a good electrical connection would be for the connection become part of the air hose connection ? Then a car knocker when hooking up the air hoses would have to spray contact cleaner on the electrical connection part.
It's worse than that. Remember that this connection carries 220V power, so any sideways or rotating engagement could not project forward to where any errant hand or other body part would contact it -- might even need to be a safety shutter over the contacts. Then you'd have to 'make' them firmly enough not to induce spark erosion if the connection vibrates. I would suspect the car-knocker's solution would be to use some kind of dielectric grease for the 'surround' lubrication, rather than blowing it off clean.
Another consideration has to be the number of terminations and potential areas of QoS loss with all the connections in what amounts to a data network. I suspect that the BITE equipment in the various valves and controllers of the brake system can work with this... but probably only if explicitly designed recognizing the problem.
My understanding was that a very large amount of thought and effort had gone into the current 'standard' for the Freight-Mate connectors and the design of the 'pigtails' back to the junction boxes on the car frames. These are rigged so that if anything hangs up the pigtail pulls loose safely at the box end, and then can be easily field-replaced ... or so goes the theory. I would think that if industry could have evolved either a modern Tomlinson approach to the electrical conductors, or incorporate them as noted into the air-hose gladhand, for loose-car-compatible operation or for blocks of cars intended to be run when necessary in normal service, the approach would have been either better tried or better documented. (Passenger railroading is distinctly different...)
BaltACDWould have to be totally reengineered for a rail use...
No doubt in my mind that they'd have to be ruggedized and then some. The cable would probably have to have a strengthening cable within it which would be tied to both the plug and the car as well.
The main thing is that there is no latch, as such, so the two connectors could easily be pulled apart, and that they are sexless.
On the other hand, if the ruggedized version was anything like the HEP cables we use, what a pain...
tree68 BaltACD Would have to be totally reengineered for a rail use... No doubt in my mind that they'd have to be ruggedized and then some. The cable would probably have to have a strengthening cable within it which would be tied to both the plug and the car as well. The main thing is that there is no latch, as such, so the two connectors could easily be pulled apart, and that they are sexless. On the other hand, if the ruggedized version was anything like the HEP cables we use, what a pain...
BaltACD Would have to be totally reengineered for a rail use...
I think these are the ones we use in Australia...
http://www.uic.org/cdrom/2001/wcrr2001/pdf/sessions/1_6/465.pdf
See figure 4. It is sexless, has a latch but is designed to survive being pulled apart.
As far as I've heard there have been no problems.
There is apparently a radio alternative illustrated (figure 3). While I spent much of my wasted youth looking at that exact type of ore car from that angle, I know nothing about radio ECP brakes and that company uses the standard connectors on their cables now.
There are details on pages 19 and 20 of
http://www.nyab.com/media/nyab_1/documents_1/technical/instructionpamphletsip/IP-237.pdf
Nothing needs to be developed. It's all there waiting to be purchased from well established USA companies.
It's been used for 11 years in Australia in daily service with no particular problems, and I don't believe our crews are any more gentle than those in the USA.
Euclid The only critical feedback that I have ever heard about ECP brakes in the U.S. testing experience has been about the connector problem. Here is a USDOT report from 1999 showing a connector on pages 17 and 18. http://ntl.bts.gov/lib/42000/42700/42740/ord9907.pdf It says that the earlier connector design had experienced problems during testing on Conrail, and had been redesigned to overcome those problems, and the new design is shown on page 18. I conclude that the problem has been solved. Are these connectors made to decouple by the pull of the cars when cars are uncoupled and separated? Or must an operator depress the spring button, and pull the two connectors apart by hand?
All the connectors in Australia are the AAR standard design.
I believe the connectors are designed to pull apart but I would expect that they would normally be disconnected manually by depressing the buttons.
I note that positive locking was one of the deficiencies raised in the USDOT report.
Of course, the trains don't get pulled apart very often. In the Hunter Valley, a train is given a number, painted on a small metal plate displayed on the nose of the lead locomotive, so the actual rake of cars can be identified, rather than the train's numerical identity in the timetable. Service tracks are provided so that empty trains can be inspected end to end while the locomotives can be refuelled and sanded still coupled to the train.
I expect that the connectors that see the most use would be between the locomotives and the train and between locomotives and I'd expect that these would be disconnected the same way as MU cables between locomotives.
The GPS-assisted Herzog ballast trains have electrical connectors between the cars. They uncouple themselves when you cut the train. They look similar to the ones in the report Bucyrus cites.
The opinions expressed here represent my own and not those of my employer, any other railroad, company, or person.
EuclidHere is a USDOT report from 1999 showing a connector
Some indication of scale would have been nice in the picture - as it is, one can't tell if it's a half inch across or 6" (not Euc's fault).
This image shows that a little better:
tree68 Euclid Here is a USDOT report from 1999 showing a connector Some indication of scale would have been nice in the picture - as it is, one can't tell if it's a half inch across or 6" (not Euc's fault). This image shows that a little better:
Euclid Here is a USDOT report from 1999 showing a connector
There were similar views in the NYAB operator manual I posted a link to...
Of course, I can see the real thing on trains with an empty and a loaded passing East Maitland every fifteen minutes each and more than half the trains having ECP, so I hadn't considered the scale as being important.
The point is that you don't have to find a seventeen year old photo, the connectors and the rest of the system are in daily use, everything is off the shelf ready to use and all that has to happen is to decide to use it.
Perhaps a repeat of my post of last June touching on some aspects of the ECP session at the Heavy Haul Conference in Perth might be of help here.
Some interesting takeaways from sessions at the recent international heavy haul conference. In a conversation with Gary Wolf, probably the best independent derailment investigator in North America, he felt that the advantage of ECP brakes in emergency is so small that he felt the mandate was totally unjustified. This was further reinforced by a paper from China that, among other things compared emergency stopping distances of ECP and conventional braked trains for a variety of train sizes and speeds. On the graphs shown, the distance difference was almost imperceptible.
In a bit of a surprise they showed a graph (that was not in the published paper) that seemed to show that longitudinal forces were higher in the ECP trains in emergency braking. Unfortunately the graphs shown had Chinese legends and the author was unable to understand questions in English, so that's a bit of a mystery.
The chairperson of the AAR air brake committee made a presentation on the state of the art in ECP. One of the issues related to unreliability of the system is cross talk between trains. Yes I know it's a wire line system, but when passing train A can hear messages leaking from train B and vice versa. If a locomotive detects a message from a car not in its consist it will initialize a penalty application. The spec is being revised so messages now include train number as well as car number. This is said to mitigate but not eliminate the problem as crossover messages will be ignored but will still consume coms capacity and may result in a time out penalty application. There have also been some issues with the connectors as they get older and wear, resulting in moisture penetration and ground fault failures. There is a search for a new connector.
It was noted that the committee feels that the tank car mandate will need to be an overlay resulting in dual systems on board the affected cars. The current cost estimate is in excess $6000 per car.
Sharma & Associates presented some work they did on predicting the probable number of punctures in various tank car derailment scenarios. They noted that there were so many variables and a wide range of potential values for each that an exact value was impossible to predict. The study used chaos theory ( noting that derailments are chaotic events) to estimate a most likely result but noted for any given derailment an exact value was impossible to determine.
Buslist Perhaps a repeat of my post of last June touching on some aspects of the ECP session at the Heavy Haul Conference in Perth might be of help here. Some interesting takeaways from sessions at the recent international heavy haul conference. In a conversation with Gary Wolf, probably the best independent derailment investigator in North America, he felt that the advantage of ECP brakes in emergency is so small that he felt the mandate was totally unjustified. This was further reinforced by a paper from China that, among other things compared emergency stopping distances of ECP and conventional braked trains for a variety of train sizes and speeds. On the graphs shown, the distance difference was almost imperceptible. In a bit of a surprise they showed a graph (that was not in the published paper) that seemed to show that longitudinal forces were higher in the ECP trains in emergency braking. Unfortunately the graphs shown had Chinese legends and the author was unable to understand questions in English, so that's a bit of a mystery. The chairperson of the AAR air brake committee made a presentation on the state of the art in ECP. One of the issues related to unreliability of the system is cross talk between trains. Yes I know it's a wire line system, but when passing train A can hear messages leaking from train B and vice versa. If a locomotive detects a message from a car not in its consist it will initialize a penalty application. The spec is being revised so messages now include train number as well as car number. This is said to mitigate but not eliminate the problem as crossover messages will be ignored but will still consume coms capacity and may result in a time out penalty application. There have also been some issues with the connectors as they get older and wear, resulting in moisture penetration and ground fault failures. There is a search for a new connector. It was noted that the committee feels that the tank car mandate will need to be an overlay resulting in dual systems on board the affected cars. The current cost estimate is in excess $6000 per car. Sharma & Associates presented some work they did on predicting the probable number of punctures in various tank car derailment scenarios. They noted that there were so many variables and a wide range of potential values for each that an exact value was impossible to predict. The study used chaos theory ( noting that derailments are chaotic events) to estimate a most likely result but noted for any given derailment an exact value was impossible to determine.
I was at the Heavy Haul Conference in Perth last June...
Where did you post last June - not on this thread which is much more recent.....
I didn't go to the Chinese presentation of ECP braking, partly because I felt (and still feel) that we in Australia would be way ahead of China in the application of ECP braking and I felt (and still feel) that the advantages of ECP braking are so well established as to not need academic papers in support.
I had just spent a full week in the Pilbara where most of the trains are ECP equipped. I must have seen thirty ECP trains pass eachother at speed on double track or more slowly in sidings on single track, and not one suffered from an unexpected emergency application of the brakes while I was watching.
Did you take up the offer of the side trip to Port Hedland to inspect Fortescue Metals which run an all ECP operation. Even their ballast hoppers have ECP brakes.
I have been watching ECP trains pass in the Hunter Valley and in Central Queensland, where many sections of line have four or three tracks and the main lines are double track for the eleven years that ECP trains have been operating and I have never heard of, let alone seen a brake application initiated by crosstalk from the cables. I myself must have seen hundreds of empty and loaded ECP trains pass eachother at both high and low speeds on normally spaced double tracks. Clearly these trains did not have any new software to prevent crosstalk, certainly not back in 2005, and my feeling is that the probability of this occurring must be very small, since I've never heard of it happening on any of the systems using ECP in Australia. Where was this problem experienced, and how often has it occurred?
However, a colleague who was with me at the conference is fluent in both Cantonese and Mandarin, and if you can give me the Title of the paper and the name of the Presenter, I might be able to get details of the offending diagram translated, and we can know for sure whether the forces are higher or lower with ECP braking. He has good contacts with the organisers of the conference, and might be able to get a copy of the slide from them.
I don't understand the emphasis on emergency braking. ECP is significantly better in normal service braking that in general occurs much more often than emergency braking, and improved service braking is where the improvements in throughput and savings in operating costs come in.
Block oil trains would be a good place to start using ECP braking, since the tank cars are almost all owned by leasing companies and converting the tank car fleet would cost the railroads very little, even if the tank cars were all dual equipped.
Have any oil tank car derailments occurred in a scenario where greatly improved emergency braking would have avoided the problem? Certainly where a rail has broken, the emergency application occurs after the damage has been done.
In earlier posts I've suggested that the faster application of brakes on the trailing section of the train AFTER a derailment would reduce the damage, and this feature of ECP braking might not be reflected in a theoretical calculation of braking distance compared to a Westinghouse system.
But it seems to me that the US railroads are "cherry picking" data to support the conclusion they have already reached that ECP braking poses insurmountable problems.
Meanwhile, the railroads in the rest of the world are fitting ECP brakes conforming to AAR standards using their own money simply because they expect to get an early return on their investment.
If you look hard enough, you'll probably be able to find some possible technicality that might cause problems.
But in Australia, the ECP trains just keep running, day in day out, with no cross talk, no unexpected brake applications, running faster and saving money on wheels and brakes.
M636CI was at the Heavy Haul Conference in Perth last June... Where did you post last June - not on this thread which is much more recent.....
Rather different views on ECP in Australia and likely even the conference in Perth by two folks in the field.
C&NW, CA&E, MILW, CGW and IC fan
M636C I don't understand the emphasis on emergency braking. ECP is significantly better in normal service braking that in general occurs much more often than emergency braking, and improved service braking is where the improvements in throughput and savings in operating costs come in. Have any oil tank car derailments occurred in a scenario where greatly improved emergency braking would have avoided the problem? Certainly where a rail has broken, the emergency application occurs after the damage has been done. But it seems to me that the US railroads are "cherry picking" data to support the conclusion they have already reached that ECP braking poses insurmountable problems.
1) Simultaneous application throughout the train.
2) Quicker stopping.
M636c, would I be correct in assuming that the connector cables pull apart automatically just like air hoses when cars are uncoupled? If yes, and combined with the dual ECP/mechanical triple valve setup discussed earlier that would solve interoperability issues, and the successes in Australia and on Cartier would suggest a lack of sensitivity to hot/cold/dry/wet conditions. Sounds proven to me, now the only remaining issue preventing widespread North American implementation is the ultra-conservative attitude of Class I upper management.
Greetings from Alberta
-an Articulate Malcontent
SD70M-2Dude M636C, would I be correct in assuming that the connector cables pull apart automatically just like air hoses when cars are uncoupled? If yes, and combined with the dual ECP/mechanical triple valve setup discussed earlier that would solve interoperability issues, and the successes in Australia and on Cartier would suggest a lack of sensitivity to hot/cold/dry/wet conditions. Sounds proven to me, now the only remaining issue preventing widespread North American implementation is the ultra-conservative attitude of Class I upper management.
M636C, would I be correct in assuming that the connector cables pull apart automatically just like air hoses when cars are uncoupled? If yes, and combined with the dual ECP/mechanical triple valve setup discussed earlier that would solve interoperability issues, and the successes in Australia and on Cartier would suggest a lack of sensitivity to hot/cold/dry/wet conditions. Sounds proven to me, now the only remaining issue preventing widespread North American implementation is the ultra-conservative attitude of Class I upper management.
I've never actually seen them pulled apart but I believe the design does allow that.
They can be separated manually by depessing the spring loaded buttons on the latches, but these should also allow the connectors to pull apart without damage.
However, I belive that the Australian experience shows that unit trains can be progressively converted with little or no disruption to the remainder of the conventional traffic.
As an aside, the standard AAR connectors are used by all systems operating ECP in Australia, even those on different gauges where there is no possibility of interchange.
I think that if USA railroad managers had closely inspected the operating ECP trains in Australia last June they would have had to reconsider their position.
M636CI think that if USA railroad managers had closely inspected the operating ECP trains in Australia last June they would have had to reconsider their position.
I would opine that there are only two things that will cause US railroads to adopt ECP:
1. Government Regulation
2. Proving that ECP has an ROI sufficient to make it worth their while (ie, increasing the bottom line).
At this point, #1 hasn't come into play for general railroading, and #2 hasn't shown it's face or ECP would be delayed only for lack of parts.
I am so damn tired of this stupid posting interface kicking you out for hitting the wrong arrow key by mistake, after it throws you somewhere else in the post at random when you try to use italics or boldface. It doesn't appear to be machine- or even platform-specific, so I conclude it is either a bug or misconfiguration in the Kalmbach site code. Why can programmers not figure out how to program for actual people?
I suspect much of the objection by American railroads to ECP involves the great investment in 'stranded cost' proprietary equipment, systems, and associated maintenance and training to make even a limited change within current operating models. In my opinion, the net effect on safety is reduced, rather than improved, in a scenario where train-handling comes to depend on improved ECP performance that 'may or not' be present in an actual train; I believe this mirrors the same phenomenon during the long introduction of air brakes 'as mandated' in the early days of Government 'safety regulation' involving Lorenzo Coffin et al.
I also suspect there is a certain industry reluctance to be the 'early adopter' that pays all the costs for the learning and acceptance curves, and the initial prices before production and aftermarket bring the unit costs down and 'commoditize' many of the parts and standards. With reference to 'reading between the lines' in the posts regarding the Heavy Haul conference -- where were the Australian papers and commentary/questions on the Chinese presentation? Where are the non-manufacturer papers and discussions, even now, that make the right 'business cases' for ECP adoption (even in the absence of likely support or even toleration from the AAR or cognate organizations)?
I personally find it outright astounding that either WABTEC or NYAB hasn't issued a pointed position statement or white paper that clearly defines how their system does both service and emergency braking, and equally clearly deconvolves the confusion about 'emergency' and 'service' stopping time and distance in clear, unequivocal English sentences. That one document, coming from a verifiable and reasonably expert source, would close down most of the waste of time, money, and talent in the current 'mandate' furball/cluster.
imho.
M636C In earlier posts I've suggested that the faster application of brakes on the trailing section of the train AFTER a derailment would reduce the damage, and this feature of ECP braking might not be reflected in a theoretical calculation of braking distance compared to a Westinghouse system. M636C
EuclidWhat do you have in mind with regard to your above comment?
What I understood him to mean was that faster setup and action helps keep as much as possible of the trailing part of the train from 'running into' already-derailed cars that have come to a stop with the usual digging-into-the-ballast kind of alacrity, at most any rate in excess of what cars can achieve with braked steel wheels on steel rails (or even, as seen in the notorious 'tornado video' steel structure sliding on steel rails or on relatively smooth ties and ballast adjacent to rails...)
The differential braking concepts still, I think, apply, but this is a very different thing from either what M636C means or what buslist has said in previous posts on this general idea.
Some of this does hinge on the idea that as soon as derailed equipment starts to dig in it is desirable or even 'politically' (or legal-liability-avoiding) necessary to put the rear part of the train in emergency ASAP to lessen the magnitude of the pileup. This whether or not up to that point differential braking were being used to keep the derailed equipment from digging in. I think it can be easily established that current systems of ECP do NOT have the capability to modulate braking in the same way they do for service -- that is part of the reason I consider the actual emergency-brake distance and time difference between regular and ECP brakes to be so tiny -- and therefore when any part of the trailing consist has to go into 'maximum effort' braking to avoid further pileup, any attempt to control what the derailed equipment is doing via differential modulation will effectively end.
Much of the effect of very quick and positive braking of a consist following an embedding derailment can be achieved with multiple inline venting of a conventional brake pipe, at vastly lower cost. In my (not very humble in this context) opinion, the complaints that have been made about problems with practical implementation of such valves (including freezing under Canadian conditions of weather, design, and maintenance) can be overcome, or systems that directly address the problem can be designed that will work in normal railroaders' practice. Perhaps that ought to be at least an intermediate priority ... but of course it would probably become an excellent case study for 'good driving out better' in the evolution of train brake systems.
EuclidMy concept of differential braking retains the faster application advantage of ECP on the entire train, but withholds some of the braking force on the cars ahead of the derailment.
So does mine. I'm just pointing out where the differential braking attempt needs to be discarded and the throw-out-the-anchor type of emergency braking would start to take its place. In part this is because any developing derailment is going to part that communication/power line, and you MUST have the brakes in failsafe before that happens. Might as well be in mechanical emergency as be trying to modulate brakes that no longer 'hear' you or can respond electrically...
As I think both I and my father have argued previously, we think it is a 'better' idea to keep an ECP train in heavy service than in 'emergency', primarily to avoid the usual emergency-related further damage and derailment propensity. buslist and a couple of other actual industry participants disagree with this, and I for one do not even propose to suggest that this 'difference of opinion' means that they are 'wrong'. Note particularly here that my method of ECP control calls for some distributed 'backup' modulation and actuation method other than that from a patent 220V 'cable', so maintenance of some, even all necessary modulation for differential segment braking and wheelslide reduction is preserved even if cars twist enough to compromise the line or the train parts. Be sure that when yours does, too, that the previously-expressed concerns about crosstalk, false 'safety' or penalty applications, etc. are addressed...
EuclidRegarding the point of whether this is an “Emergency” application or a “Service” application, I do not entirely understand how these are distinguished in an ECP system.
If you read the technical documentation for either the NYAB or WABTEC system, you will get this. In a typical system the ability to 'big-hole' the pneumatic part of the system is retained, essentially 'downstream' of the modulating electric valve. Emergency then consists of full line pressure to the cylinders, the 'difference' in setup speed being only that the electric "bypass" valves all operate immediately, and a bit more positively via their actuators, than a sonically-activated triple will. In addition, the available air pressure in the trainline is 'full' at all times, so there may be some makeup to the main reservoirs as they supply the cylinders and thereby a higher cylinder pressure can be established earlier or reached 'at the limit'.
Modulated 'service' application, on the other hand, can use all the available ECP advantages, including different braking limit rates detected for car types or loadings. It also includes the inherent ability to use very heavy or quick application of the brakes without having to 'worry' that you'll have to 'live with the consequences of your actions' afterward until you can recharge the system enough to release the excessive set.
In any case, in my concept, the application is not triggered by the parting of the wire. It is triggered by a signal sent directly to the master controller by the affected derailment detector.
I am not saying otherwise in any respect. The 'parting of the wire' is the point at which either modulation and control power is lost to the trailing consist, or some or all the sensor input from that part of the consist becomes 'indeterminate', and while not in the disturbing sense of the Browns Ferry fire, this may be problematic if a short between the conductors compromises either the 'last known good' or 'emergency default' positions of the ECP brake valves, or compromises how those valves subsequently act under autonomous control or self-power.
The 'emergency' here would actuate not at the time the first detector activates, but at the time a loss-of-control event occurs (I think a direct parallel to the kind of issue buslist was describing, where any anomalous event in the wireline signal integrity causes an immediate 'penalty brake' to full halt for reset.) The issue is then whether subsequent reaction of the trailing brakes in your system goes directly to 'mechanical' full emergency release, or to a graceful-degrade failover of some sort in which some of the potential advantages of ECP control can be retained.
This application would be as quick as possible with ECP; on both sides of the derailment; but will follow the modulation program with some reduction of force in the cars ahead of the derailment.
The point I was making here is that it will not be 'as quick as possible with ECP' on the trailing part of a wireline-controlled system (you say you no longer have either RF or inductive control modality) - as soon as the signal integrity is lost to the trailing consist, you will at best be using some sort of AI or expert-system emergency self-modulation of that part of the brake system. Much more likely, you will be in full emergency at that point in an all-out effort to keep even one car from accordioning into what is soon to be a very substantial and stopped obstacle to the trailing cars.
Now, what happens to the brake application of the consist ahead of the derailed cars, especially as those cars may be dragged by their couplers and in fact may be starting themselves to overturn, is a separate issue. Here buslist et al. also think full emergency (to get the momentum of 'the inevitable' as low as possible before the rolling starts) is the most appropriate response to go to. The 'catch' here is that the derailment sensors on any of the cars in this section aren't providing you with 'additional information' you can use for the modulation decision, other than to give a heads-up and a record of how the actual derailing progressed over time. What you need are the differential draft-gear tension and extension sensors, and I have been tempted (although not very far, up to now!) to modulate the 'differential braking' so as to actually try to get a knuckle as close as possible to where the derailed cars are connected to the as-yet-underailed part of the train... then actually retard the braking rate to ensure that an underailed leading portion won't be run into, and perhaps further damaged or derailed, by whatever is 'known off the track' to enough extent to part the line. (Railroaders will be laughing hysterically at this point, but it does represent one of the branches that control theory reaches when this extent of brake modulation can be provided.)
EuclidI have not correctly stated my thoughts about modulation above. When I ruled out the wireless control for modulation, as I mentioned above, I ruled out modulation as well. I should not have used the term “modulated response” in my second paragraph. Instead, it would be a predetermined response of lower braking force on the leading cars compared to the maximum force response on the trailing cars. But it would be the same force throughout the stopping time. This predetermined response would be determined by the variety of train characteristics that I mentioned above.
This is a place where you and I wildly disagree.
Even my father's old system for Conrail circa 1988 'modulated' the train-brake application continuously over time, and he thought necessarily so, so as to avoid the then-significant problems that occurred with 'positive train control' brake application of the sort suitable for passenger or commuter consists when applied indiscriminately to a much longer freight with unpredictable makeup or braking characteristics.
In my opinion it would be completely pointless to even attempt doing stretch braking with two 'average' brake applications on two halves of a foundation-braked train, even if the physical brake action were continuously proportional and progressive (which it is certainly not!) You will very quickly have a systemic and increasing load (and remember it HAS to stay in tension; even a moment's compression or run-in means almost assured disaster) that will involve very substantial inertial mass backed up by a large amount of aggregate friction and contact area. So when the draft-gear travel goes out you will essentially have the whole force yanking on one of a very few couplers in the derailed portion of the train. And if the derailed portion decides to dig in, it will bring its considerable deceleration to bear on the leading coupler connection, which will snap something and result very quickly in 'divergence' of the now-unguided first car and probable establishment of accordioning.
In my opinion, we need a better (and more detailed) description of exactly what the 'derailment detectors' consist of, how they operate, and how they are arranged to gracefully degrade where possible. There are a number of different modes of derailment, each of which may 'deserve' or demand its own specialized response that needs to be implemented no less quickly than in seconds, with little control latency given the comparatively long response of the actual power-braking foundation on current freight cars. But modulation fore and aft of a 'differentially-braked' supposed derailed car, whether or not trainline continuity is lost, is desirable to preserve. (Lest the cure become worse than the disease...)
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