Oil Train

[Euclid]

Wizlish

 

Euclid

I suggest to the inventor that he place a single, larger surfactant reservoir on the outside of the oil tank. It might be something like a saddle tank or saddle bag that occupies some of the available space between the oil tank and the clearance diagram.

 

 

With respect, you're looking at the wrong thing. 

 

Wizlish,

I had no intention of choosing the “right thing” to look at.  So I find it odd that you would take issue with that point.  My point is to look at one thing out of many.    

I only tossed the invention by Iman Chalibi on the table in case you or others wanted to comment about it.  I have no stake in it.  I am not defending it.  Like you and others, I see lots of practical problems with the idea.  I am just adding my thoughts about the storage tank to the list of comments because nobody has mentioned it. 

When I suggested a saddle tank or saddle bag, that just a general description of an external tank.  Specifically, the best location would be on either side of the lower half of the oil tank.  Unlike other types of rolling stock, tank cars have free space in the quadrants of the tank circle.  So why stuff the extra equipment of this invention into the payload tank when it can be hung on the outside where it will be easier to inspect and maintain? 

[Wizlish]

BaltACD

Doesn't water still freeze at 32 degrees F?  With Baaken crude coming from the Dakota's - winter temperature there and through most of the Northern US and Canada is well below 32.

There will be some freezing-point elevation from the surfactant if it is well chosen.  Obviously not sufficient for a Canadian winter.  I'm certain the inventor knows ... or ought to know ... that his water needs to be kept well insulated, probably with one of the modern nanoinsulation techniques like aerogels, and provided with some sort of heat-tracing arrangement to keep all the pipes and nozzles open.

In partial defense of my entirely non-serious location for the manifold: if the oil is kept at some reasonable temperature to make it ready to flow upon arrival, this will automatically keep water mixture in tankage 'within' the oil volume at proper temperature also, while minimizing the number of penetrations needed in the actual tank shell and the insulation and heating arrangements needed externally.  Someone like Midland Mike is much more conversant than I am with the specific methods used to make the oil fluid, but not excessively 'hot', for best terminal handling.

[BaltACD]

Doesn't water still freeze at 32 degrees F?  With Baaken crude coming from the Dakota's - winter temperature there and through most of the Northern US and Canada is well below 32.

[Wizlish]

Euclid

I suggest to the inventor that he place a single, larger surfactant reservoir on the outside of the oil tank. It might be something like a saddle tank or saddle bag that occupies some of the available space between the oil tank and the clearance diagram.

With respect, you're looking at the wrong thing.  Read tgmidget's post again, and then look at what the inventor claims is the advantage of his 'surfactant' approach.  The added capacity needs to be the water that forms the emulsion.

That is a sizable mass of water.

The amount of surfactant, whether biodegradable sorbitan-based or more powerful, is easily accommodated in the size and location of the mini-tanks the inventor mentions.  I do not think you can provide sufficient tankage for the required water mass in that location, or make the railcar's dynamics as a moving vehicle at all satisfactory if you were to try.  This gives you the delightful opportunity to propose where the tanks for the emulsion water should go, whether the surfactant (or some other adjuvant material) will act suitably as antifreeze in the often-harsh Canadian climate, and how the water as well as the surfactant will be meaningfully admixed with the crude.

Let me repeat here, before we get arguing about the wrong things, that it does not appear that this 'version' of the system is really intended to protect against impact problems.  It's much more directed against fire resistance and 'environmental protection', which probably permits slower and less energetic/dangerous mixing than the kind of oil-train protection systems we've been discussing in this thread would need -- and that no few of us have been tacitly assuming this Canadian system would use.  It remains to be seen if the system can, in fact, be made quick-acting, and I basically agree with the midget that it really can't be.

I am beginning to think that the only really "practical" way (this is like the first law of consulting; even the 'most practical solution' may not really be practical or suitable, or much of an actual solution, at all!) to disperse the water and surfactant adequately and then assure mixing is to have some kind of manifold within the tank volume, running a good percentage of the length of the tank if not in fact full length, with nozzles all up and down it, which contains the surfactant and water and is pressurized upon 'activation' to produce spray radially outward.  This will decrease the payload volume, but perhaps not uneconomically so considering the car cannot be operated 'full' for other reasons, and the provision of the safety system might allow thinner shell gauge, or reduced armoring or thermal insulation on the shell.

[Euclid]

I suggest to the inventor that he place a single, larger surfactant reservoir on the outside of the oil tank.  It might be something like a saddle tank or saddle bag that occupies some of the available space between the oil tank and the clearance diagram.  The only part of the system that would penetrate to the inside of the oil tank would be a series of surfactant injection nozzles.  Likewise the electronic controller would be on the outside of the oil payload tank.

[tdmidget]

There's dumb ideas but this one takes the cake. Any thing that could mix 30,000 gallons in seconds would be more violent than the potential release of the product. In addition he claims to have "surfactants" but they are useless with out a supply of water. All in all, this is even dumber than the idiot in Canada leaving his train on air.

[tree68]

Wizlish

The difficulty with steam in the emulsion is as I indicated above: if the water in an emulsion superheats and then phase-changes in a rupture, the effect may be dramatically worse than with crude alone.

As I recall, water is sometimes added to the exhaust of jet engines to increase their thrust.  Water in an enclosed container will "BLEVE" just as well as any flammable substance, except that pure water obviously won't burn.  Water mixed with a flammable substance, however, may well be dramatically worse, as you note.

[Wizlish]

These and Balt's questions are good ones.  I do suspect that many of them can only be answered by the inventor with "TBA" as he specifically notes that details of how and what the sensors do, and how they activate the chemical 'suppression' system, are not part of what he's discussing.  In my opinion there are some commonsense answers and perhaps theoretically 'best practices' in how the actuation would be done, but at this point the inventor is concentrating on what happens when the suppression device is triggered.

dehusman

A couple questions that are unanswered: 1. What powers the system?

The sensors will probably generate an electrical signal.  The actual 'power' to inject the agent and mix it with the mass of oil in the car will probably involve either pressurized gas or some sort of gas generator (which I think, at the speed and volume required, would almost certainly involve pyrotechnics, hypergolics, or energetic chemical reactions of some sort). 

2. What triggers a release of the chemicals? Derailment or breaching?

Presumably something very severe -- much more severe than any usual longitudinal buff shock or suspension vibrations.  My suspicion is that there will be several parallel 'sensor' systems that would be involved, and that in some cases multiple systems would need to activate in order to fire the irreversible reaction. 

In my opinion, breaching is FAR too late; the energy involved in injecting and mixing the agent would surely have the effect of presurizing the contents and ejecting some from the breach, likely inducing precisely the effect, albeit at smaller scale, that the system was intended to avoid.                           

 

I would say the most logical approach at present would be to use the Spanish-style derailment sensor; it would make at least as much sense to use this (delayed if desired) for cargo passivation as to trigger an unexpected emergency event.

3. Does it activate the whole train or just the cars involved?

To me, common sense would dictate that the system only operate on cars actually involved in an immediately dangerous condition.  Removing crosslinked 'solidified' oil even from a layer blanketing the tank walls is going to be a seriously expen$ive operation.  Purifying the emulsified load is likely to be bottom-line expensive, too, to say nothing of the delay in receiving the feedstock. 

4. Does it activate the cars in the area or just the cars involved?

Agqin, I would think the 'prompt' system wold only work on actual endangered cars during the accident.  Yes, there would probably be delayed temperature sensors that would activate the system on 'nearby' cars if fire from another source threatened them, or perhaps if someone in authority decided to 'safe' those cars.

5. Does it differenciate between loads and empties?

This is an interesting question, and it will be interesting to see if the inventor realizes it.  This is comparable to whether or not you fire the inertia-reel tensioner on an automobile seatbelt that is not buckled around an occupant -- note the added system complexity and potential points of failure or false triggering that are introduced.

There is also the question that even "empty" cars will contain considerable hydrocarbons and may benefit from passivation,  In my opinion it would be suboptimal to design a 'partial release' of the agent in the mini-tanks depending on the relative fullness or liquid level of the material in the car -- it would either fire 100% or be kept safed for empties.  One of many considerations is whether a separate safety provision -- say, pressurization of the car with nitrogen -- is detected, tested for, and allowed to keep the safety system turned off. 

6. How fast does it deploy, how fast does it activate?

Note how carefully the inventor does not answer this.  It is possible that the actual 'mixing' time could be longer than the accident duration, but the typical public assumption would be that it does whatever it does to 'safe' the cargo before an explosion can develop, and that is a comparatively short time (during which the detection, actuation, full deployment and mixing of the agent, and a great deal of the subsequent reaction all go to completion).  As noted, I think any system capable of roiling light crude this much in this short a time is a terrifically hazardous thing if there is a large percentage of dissolved hydrocarbon that wants to be in the gas phase at ambient temperature -- as there was in much of the Bakken and Eagle Ford crude shipped up until recently.

7. An additional failure mode not addressed is when the car is heated by fire and the car fails due to pressure from the heated commodity and weakening of the tank wall. What happens when the treated oil is heated, do the chemicals continue to behave in a protective mode?

The emulsified oil will take a much longer time to heat up due to the large heat capacity of the water content.  I do not know if heated emulsions of oil outgas substantially before the water reaches the boiling point.  I would be nominally concerned about the possibility of a steam explosion acting to vaporize superheated emulsion, with the dry steam at an elevated 'flash' temperature posing comparatively little resistance to ignition of the oil content. 

I would expect some tendency for the crosslinking bonds to break at elevated temperature, but also some tendency for further crosslinking at moderately elevated temperature.  The result might tend to char instead of degrading to flammable oligomers.  I don't yet know enough organic chemistry to do more than speculate, but someone with distinctive competence can give you a minute-by-minute discussion of what happens as solidified oil is heated.

Does the treated oil have less of a tendency to rupture when subjected to heat? Do the chemicals have any effect on the volatiles dissolved in the oil?

This is two questions that I think have very different answers.  The emulsified oil will have much less tendency to rupture when heated, compared to untreated crude oil.  The difficulty with steam in the emulsion is as I indicated above: if the water in an emulsion superheats and then phase-changes in a rupture, the effect may be dramatically worse than with crude alone.

I do not think either approach works on the volatiles, and this is a severe potential shortcoming that I don't think 'matters' to the inventor, although for HHFTs I think it should.  It's an interesting consideration whether an agent might react with volatile monomers in a way that condenses them effectively, either by reaction or crosslinking.  I'm of the impression, though, that an agent that could do this adequately with the considerable volatile content of Bakken or Eagle Ford crude would react with considerable exothermia -- which is not a good thing here.

[dehusman]

A couple questions that are unanswered:

1.  What powers the system?

2.  What triggers a release of the chemicals?  Derailment or breaching?

3.  Does it activate the whole train or just the cars involved?

4.  Does it activate the cars in the area or just the cars involved?

5.  Does it differenciate between loads and empties?

6.  How fast does it deploy, how fast does it activate?

7.  An additional failure mode not addressed is when the car is heated by fire and the car fails due to pressure from the heated commodity and weakening of the tank wall.  What happens when the treated oil is heated, do the chemicals continue to behave in a protective mode?  Does the treated oil have less of a tendency to rupture when subjected to heat?  Do the chemicals have any effect on the volitiles dissolved in the oil?

[BaltACD]

How much payload capacity is sacrificed in implementing this 'solution'?  How much of the catalytic agent is required to perform the chemical reaction on a fully loaded car (nominally 30K gallons for both oil and catalyist)?  Is the reaction endothermic or exothermic?  What is the specific trigger mechanism that causes the deployment of the catalyist?

[Wizlish]

All this longwinded ... discussion.  Go back and watch the video again, and think about what you're watching this time.  I grant you I find it a bit difficult to read the blurred text while that music is playing, but it can be done.

It would obviously make no sense to attempt to emulsify and crosslink at the same time -- you're quite correct to say your BS detectors go off.  The inventor's syntax could be clearer, but he makes clear these are two different options that use the same tank and dispersal technology.  If in doubt, we could always contact the inventor directly -- he can't be hard to find, and apparently has an actuve YouTube presence -- and ask for better technical details.

Spend five minutes googling 'norbornene' or the category of solidifiers, and then google crosslinking and polymerization if you are not familiar with how that works, and then review what a gel is, chemically and physically.  I suspect the Canadian material just uses the word 'gel' to make people understand that the invention "thickens" the oil, but a gel is a specific phenomenon and what is happening here is different.  (That is good, because I suspect a true gel would be poor at resisting the forces in a typical railroad tank-car accident, but that's another discussion).

You HAVE to do more than literary criticism when understanding engineering discussions.  Both the sources and the science are freely available on line -- so use them, instead of whining about why you don't understand, and raising further confusions.

So overall, I don’t know how you know that the inventor was not saying what he said.  

This being a classical example.  Attempting to actually answer this statement would not produce any particular light.

If you understand what the invention is supposed to do (which is possible from the video) and how the chemistry involved works (which is not exactly rocket science) you can figure out what the inventor meant, and not get lost in the sauce of 'saying what he said' according to what you thought he said.

This is distracting from the actual point here, which is whether a system that injects an agent ... or a combination of agents that are complementary, either together or sequentially ... to make the oil less hazardous in situ or as released can work to decrease the risk of explosion and fire on impact.  This should be separated from the use of such a system for other purposes mentioned in the video and story, such as the health of responders who might be exposed while clearing up an accident minutes or hours after it occurs, or the health of wildlife or people whose drinking water is affected by runoff after a spill.  Personally, I think there are problems with injecting anything at high speed (and presumably reasonable volume) into Bakken or Eagle Rock crude, and those problems should be addressed and, if possible, some solutions developed for them that would work in the 'real world' of oil shipment.

[Euclid]

Wizlish,

You said this: “Part of the 'answer' is that you, like the flack who wrote the news story, haven't quite understood what the inventor was saying.”

How am I supposed to understand what the inventor is saying and know that the “flack who wrote the news story” does not understand what the inventor is saying when all I have to go by is what the “flack who wrote the news story” says the inventor is saying?  In any case, the invention is also explained in the video.  Perhaps the same “flack who wrote the news story” also produced the video, and that’s wrong too.  But I doubt it.

You said this: “The system only uses one of the two 'agents' at a time, not both, depending on what is desired.”

On the contrary, the explanatory video, which I assume was produced by the inventor and not the “flack who wrote the news story”, says that the surfactants and the Norbornene are both released upon impact.  That sounds to me like the two chemicals are both used at the same time. 

Can you explain how the two chemicals are only used one at a time, depending on what is desired (as you say) when both are released upon impact?

You said this: “The norbornene (that you can't spell it indicates to me that you don't know what it is or what it does) does not form a "gel"

Both the explanatory video and the news story refer to the Norbornene converting the oil into a “gel.”

So overall, I don’t know how you know that the inventor was not saying what he said.   

[Wizlish]

Part of the 'answer' is that you, like the flack who wrote the news story, haven't quite understood what the inventor was saying.

The system only uses one of the two 'agents' at a time, not both, depending on what is desired.

The surfactant approach uses a biodegradable detergent to form an oil-water emulsion, not to 'thin' the oil, but to reduce its tendency to ignite.

The norbornene (that you can't spell it indicates to me that you don't know what it is or what it does) does not form a "gel" - it crosslinks the liquid alkanes in the oil.  It is an example of a class of materials known as 'solidifiers', and I suspect Midland Mike among others will be very familiar with the existing use of these in cleaning up oil spills on water.

Neither of these approaches appears to address what I consider a major actual problem with these light crudes: the high volatile and gas content.  Light hydrocarbons in the gas phase are unlikely to form emulsions or be dissolved in them;  I also wonder whether norbornene, which is a crystalline solid over much of the range of expected shipping temperatures, can be made to admix with vapor effectively.

There is also the question of the technology which rapidly injects these agents and assures full turbulent mixing.  This either involves high gas pressure or some means of near-explosive gas generation.  I would be concerned with the range of safety problems that providing this on existing tankcar shells (which is the primary stated initial intent of the inventor) would entail.

I am glad to see that the discussion of the sensor suite is no longer a 'hot' topic.  It does not matter to the invention what methods or systems of sensing are used, only that at some point an accident condition is detected and the pressurized mixing of the agent in the "mini-tanks" is initiated.

[Euclid]

What I don’t understand is that he uses surfactants which I understand would tend to thin the oil. But then at the same time, he uses the Norborene to thicken the oil.  

[MidlandMike]

Years ago a system that turned jet fuel into gel during a plane crash was proposed, but never adopted.

[Deggesty]

Another question: how fast will the gel flow out of the car once you have the car in a safe place for emptying? Is there a compound that can be added so that the contents will again be liquid? Or will you perhaps have a trainload of unusable and unrecoverable gel?

[Electroliner 1935]

Next comes the cost study. How much does it cost to install all this added equipment and weight to the cars. What's the cost that the shipper can accept before he says "No, if you want me to do that, then I can't sell my oil" ? It's an interesting proposal but it may be uneconomical. 

 

[Euclid]

New Invention for Safer Oil Trains

 

Here is some new thinking about another approach to the problem.  It does not prevent derailments or pileups.  It does not prevent sparks for ignition in a wreck.  It does not prevent tank cars from rupturing or prevent oil from spilling.  It does not extinguish a fire.

 

What it does is instantly convert the oil cargo from flammable to much less flammable upon the sensing of a derailment.  At the same time, it also turns the oil into a gel which slows down its ability to leak and spread upon a breaching of the tank.

 

The concept uses sensors to trigger the response, but it does not explain these sensors or how they command the response.

 

Is this possible or practical?  Could the entire oil load be converted quickly enough?

 

General background of story:

 

http://news.engineering.utoronto.ca/safer-rail-car-wins-engineering-student-top-prize-at-minerva-safe-design-awards/

 

Detailed description of invention:

 

https://www.youtube.com/watch?v=BH9BuMZaEg0

[Wizlish]

Paul of Covington

I'm not going back to read this whole thread, but I don't remember anybody claiming that multiple EOT's would be a perfect alternative to ECP.

That's because it's not.

On the other hand, my father has been advocating multiple in-line brake valves for many years, and Dave Klepper and I had a discussion on the idea when he re-introduced the idea ... I believe earlier in this thread. 

Then, as now, I tried to get consensus on what the term for these midtrain devices should be.  For the moment assume they are dedicated device modules called MTDs.  They are obviously not "EOTs" even if you were to adapt a FRED so it could be used in midtrain (a sensible device recognizing it was in 'midtrain' because it was in the middle of two hoses and not just connected to one).  On the other hand, they would contain a GPS core for independent location (etc.) and, ideally, an addressable proportional valve (that would follow the position or setting of the 'master' valve in the cab, or the setting passed via a train control system), and some means of reasonably assured power and communication.

These get spaced every 20 or so cars in the train as it is made up - all the practical details having been worked out in detail for the patent applications.  Note that the valves do not all 'have' to respond the same when commanded, and the MTD action is separate from the 'emergency' action between the head end and DPU/EOT.

This produces a number of the benefits of ECP -- the most notable one that is missing being one of the greatest benefits of ECP for general train handling, full graduated release.  "Theoretically" you can have an approximation to that, too, using the same technology that can provide the equivalent of constant trainline supply pressure to ECP equipment in a conventionally-braked consist ... but I digress.  The answer is that DEPENDING ON THE BENEFIT YOU WANT a MDT system can provide much the same 'benefit' that can be achieved at much higher cost from ECP.  But it is certainly not a 'perfect replacement' for ECP.

[schlimm]

Given recent news that very little Bakken (and maybe also Canadian) will be shipped by rail within five years (if shipped at all), much of this issue will be a moot point.

[Euclid]

Paul,

 

I don’t know if anyone in this thread claimed that any EOT approach would be a “perfect alternative”, but I get that general implication sometimes with the single two-way EOT approach, both here and in other reports and articles.  Let’s just say it is often implied to be an acceptable alternative to ECP.  I am not sure how that judgment call should be made as to what is “acceptable” as an alternative to ECP if the performance is less than that of ECP.

 

I agree that your multiple EOT idea may match the stopping ability of ECP.  I am not saying that the multiple EOT approach is a bad idea.  We did discuss multiple EOTs again just a couple pages ago.  Wizlish had some comments about it.  If remember right, he was wondering what might be the effect of multiple, distributed EOTs sending brake dynamiting waves in both directions from different points throughout the train.  I believe the concern was about how that would affect in-train forces and their ability to cause trouble.  It is a way to compete with ECP stopping ability.  There seems to be a lot of fine points in the argument.    

 

There is one other point that I noticed in the Simulation download in David Schanoes’ blog:  The Simulation download said that stopping distance can be reduced by increasing brake shoe pressure.  It is referred to as improving the “net braking ratio.”  I was under the impression that it is common practice for brakes to be applying with as much force as possible without causing the wheels to lock up and slide when the cars are empty.  Or; with load sensors, the NBR would increase braking force to the appropriate level for when the car is loaded. 

 

Beyond that, how can you further increase the N.B.R., as the simulation piece says?  How can this already maximum brake force condition be further increased even more without causing excessive wheel slide?

 

That strikes me as odd that they would toss out that idea for quicker stopping. 

 

http://dms.ntsb.gov/pubdms/search/document.cfm?docID=429570&docketID=55926&mkey=88606

[BaltACD]

Paul of Covington

Euclid

I am also not convinced that multiple EOTs or distributed power matches the stopping performance of ECP in “Emergency” applications, and is therefore a perfect alternative as of often implied by those arguing against the ECP mandate.

   Look at page 25 of the PDF of the study.   By initiating the application at just two points instead of one, the performance goes approximately two-thirds of the way toward matching the ECP performance which initiates it at every car.   You may not be convinced, but I think that by initiating application at three or four more points, performance would be mighty close to that of ECP.

   I'm not going back to read this whole thread, but I don't remember anybody claiming that multiple EOT's would be a perfect alternative to ECP.

The 'standard' EOT in today's world of railroading is the 'two-way' EOT that is connected by radio to the locomotive - Emergency application detected by either device will trigger the emergency application on the other device.

[Paul of Covington]

Euclid

I am also not convinced that multiple EOTs or distributed power matches the stopping performance of ECP in “Emergency” applications, and is therefore a perfect alternative as of often implied by those arguing against the ECP mandate.

   Look at page 25 of the PDF of the study.   By initiating the application at just two points instead of one, the performance goes approximately two-thirds of the way toward matching the ECP performance which initiates it at every car.   You may not be convinced, but I think that by initiating application at three or four more points, performance would be mighty close to that of ECP.

   I'm not going back to read this whole thread, but I don't remember anybody claiming that multiple EOT's would be a perfect alternative to ECP.

[tdmidget]

but that is because this has taken on the ferocity of a middle eastern religion to you.

[Euclid]

Paul,

 

Thanks for posting that piece by David Shanoes.  I skimmed through it, but will read it more carefully later.  I will also study that simulation study.  Generally, I would likewise conclude that the US DOT might misunderstand the stopping distance issue, as improbable as that would seem, given the technical expertise at their disposal.

 

I am referring to the stopping distance large advantage with ECP being confined to “Service” braking applications and not to “Emergency” applications.  However, ECP does nevertheless offer some degree of advantage in the “Emergency” applications as well.  And every second counts critically in situations calling for an “Emergency” application.

 

I am also not convinced that multiple EOTs or distributed power matches the stopping performance of ECP in “Emergency” applications, and is therefore a perfect alternative as of often implied by those arguing against the ECP mandate.

 

Also, there is more to the ECP safety advantage than just stopping distance.  Those advantages include the large reduction of slack action forces, the near elimination of UDEs, and the enabling of safer train handling.  In my opinion, those three advantages of ECP far outweigh the derailment mitigation advantage of slightly quicker stopping.  But, author David Schanoes has chosen to not address those other advantages and focus only on stopping distance.

 

For a derailment mitigation benefit of quicker stopping, I believe the answer is what I call “Differential Braking,” which consists of ECP brakes, derailment sensors, and the differential braking control system.  It is what I call The Higher Purpose of ECP Brakes.

 

This system of Differential Braking would significantly mitigate or even prevent the most destructive phase of derailments.   In addition, as a part of the Differential Braking system, the basic abovementioned three advantages of ECP alone; involving slack, UDE’s, and train handling; will prevent some derailments altogether.   

[Paul_D_North_Jr]

Regarding the lessened effectiveness of ECP braking in derailment situations, see this recent pointed column/ blog by David Schanoes, dated August 10, 2015, which is pretty clear and solid analysis, IMHO:

"Friction" - http://ten90solutions.com/friction 

- Paul North. 

[Euclid]

tree68

 

Euclid

Also, in this tornado wreck, the cars down in the ditch apparently did not pile up because of their tendency to stay coupled together while being pulled along by their own momentum and the momentum of the locomotives which remained coupled to them for some time.

 

 

The cars were blown off the track en masse by the tornadic winds.  Whether they were under tension or in buff is of little or no consequence.   

It most certainly is of consequence.  After the cars were blown off the track by the tornado, they cars skidded along at 40 mph dissipating their rolling energy without piling up.  That would not have happened without draft force.  It was not the tornado that moved them along with the locomotives.

As far as being worth it, I have no idea on that call.  I think the system would mitigate pileup damage with most derailments to varying degrees, and even prevent some of them altogether.  Of course the industry would fight it tooth and nail.  But part of the cost will already be inevitable in the form of the ECP mandate (if it is not overturned), so the actual cost of differential braking is the derailment sensors and the program development and other R&D.       

 

[tree68]

Euclid

Also, in this tornado wreck, the cars down in the ditch apparently did not pile up because of their tendency to stay coupled together while being pulled along by their own momentum and the momentum of the locomotives which remained coupled to them for some time.

The cars were blown off the track en masse by the tornadic winds.  Whether they were under tension or in buff is of little or no consequence.   

In any case, the tornado video does not prove that differential braking will never work.    

It would seem, however, that there is a very limited subset of derailments where differential braking would be useful.  The question, as already mentioned, is whether the cost is worth the return.

[Wizlish]

dehusman

My contention is that if the cause of the derailment is a track related cause, then the point of derailment is fixed. Subsequent cars passing over that point are liable to derail.

But for every cause that is fixed in the track, there are others that are not -- broken wheels, lozenging, burned journals -- and a large subset of these don't produce prompt track damage like spread gauge or overturned rail ('marks on the ties' or even fractured concrete ties don't count.  For every tornado video there's likely to be a Marysville acrylonitrile fire.

The whole "keep the train stretched" scheme only works if the number of derailed cars is limited and there are cars on both sides of the derailed car on the rails to keep it in line.

This is of course true, and to paraphrase your following point a bit more forcefully, it isn't just 'friction' that causes cars to slow down more quickly than trailing cars can brake; the moment a truck frame digs in or a car's 'nose' rotates out, you're very likely to see deceleration greater than the trailing 'brake action' can accommodate.

As far as the tornado video goes, I am a loss at how differential braking would have worked since there was only one car coupled to the engine and it was off its trucks, almost on its side. There was no train to differentially brake. Other than the engines, there wasn't a single brake shoe that could be controlled from the head end of the train.

The only part of 'differential braking' that would have affected the train in the tornado video would be better control over that "leading' tank car that derailed and swung but then merrily stayed in line with the track.  In that particular case, the differential braking would have been of marginal if any use, even if it had been set up to put power on the head end to accelerate it away from collision.  (Similarly, it might not have mattered in the 1987 Chase wreck if the diesels had accelerated after splitting the switch, or even had their brakes released at the moment of impact, but under other circumstances -- remember the near-miss with the LRC? -- those actions might have made a difference.)

Differential braking is no more a 'cure-all' for derailment accident damage than ECP brake technology is.  Its proponents, at least those who are wise, don't present it that way, and in the absence of better statistics I'm not going to say its prospective benefits would justify its cost on top of the ECP equipment needed to implement it properly..  But I think there are many potential situations where it might be beneficial if ECP turns out to become mandated.

[Euclid]

Dave,

I understand your point about the tornado video.  Differential braking would not have directly intervened much because the train quickly parted.  So it is not an ideal demonstration of differential braking. 

But nevertheless, differential braking would have prevented the pileup in a relatively indirect way by naturally suppressing the brake application on whatever was left of the train ahead of the point of derailment.  In this case, it was only the locomotives.  But with their braking suppressed by the ECP differential braking program, the locomotives would have outrun the cars coming ahead from behind the point of derailment.

Also, in this tornado wreck, the cars down in the ditch apparently did not pile up because of their tendency to stay coupled together while being pulled along by their own momentum and the momentum of the locomotives which remained coupled to them for some time.  This demonstrates the desired effect of differential braking even though it was merely produced naturally by the train forces.  Had there been differential braking, that would have added to the effect to the extent that the cars in the ditch remained coupled and in line.

In any case, the tornado video does not prove that differential braking will never work.