Euclid that's exactly how ours work. If your airline pressure drops below 60 psi we get a warning light in the cab along with a 120 dB buzzer that is to remind you that hey there is a problem with the brakes buddy and pull over. If you ignore those and let your air pressure drop to 40 psi then the emergency aka parking brakes apply automatically and slowly bring you to a stop. It's about the same pressure being applied as a normal service stop. It's fast enough to get you stopped but you still have control to steer. Then once you are stopped it remains applied until you have regained pressure to override the springs not in the brake chamber but the valves themselves. So unless the valves see over 80 psi in the lines after a brake failure event on our system they won't even release the air to the chamber to release the brakes. This is on a 120 psi system. Now we do have runaway trucks sadly but those happen when drivers forget that you can climb a mountain as fast as you want as many times as you want. However you better remember slow and steady downhill wins every time.
The application sounds fairly straightforward and relatively fail-safe. Just how would said brakes be released when appropriate?
CSSHEGEWISCHThe application sounds fairly straightforward and relatively fail-safe. Just how would said brakes be released when appropriate
Probably the same way brakes are released today - the control valve senses a rising pressure in the brake pipe. It would just need to have a way to un-set whatever mechanical mechanism if holding the shoes against the wheels.
This is interesting in that, unlike ECP brakes, it seems a brake system like this could be made to be interoperable with the existing brake systems on cars. Brakes still apply and release based on the signal provided by the brake pipe. Whatever complexities get added to "set the parking brake" would be traded off against not having to have a manual brake wheel and the associated linkage.
adkrr64 CSSHEGEWISCH The application sounds fairly straightforward and relatively fail-safe. Just how would said brakes be released when appropriate Probably the same way brakes are released today - the control valve senses a rising pressure in the brake pipe. It would just need to have a way to un-set whatever mechanical mechanism if holding the shoes against the wheels. This is interesting in that, unlike ECP brakes, it seems a brake system like this could be made to be interoperable with the existing brake systems on cars. Brakes still apply and release based on the signal provided by the brake pipe. Whatever complexities get added to "set the parking brake" would be traded off against not having to have a manual brake wheel and the associated linkage.
CSSHEGEWISCH The application sounds fairly straightforward and relatively fail-safe. Just how would said brakes be released when appropriate
Just what is needed - another UNINTENDED way for brakes to be set up on a car within a train.
Never too old to have a happy childhood!
Just how are you going to switch cars off air? Especially hump yards, industrial locations that have no air to charge brake lines, my local siding that uses some type of mechanical vehicle to move cars, etc?
I'm sure there is a way to rig the system so that the same bleed rod could be made to hold the brakes off for switching purposes.
He's gonna have fun paying AAR/TTC (MxV Rail) in Pueblo to validate his concept and pick him apart in Pueblo! (while he's waiting behind the epb brake testing)
Euclid I have been looking for explanations of exactly how this new parking brake works. It is described in the TSB report of the Field, BC runaway. That report is here: #R19C0015.pdf
Cursory reading of the TSB report to me indicates that the locomotives involved were not equipped with a pressure maintaining feature to hold the trainline air pressure steady. Secondly when the train stopped and 'a job briefing was held with the Trainmaster - the TM's remedy was not sufficient for the crew to maintain control of the train - the apply retainers and 'hope' the trainline air pressure can be regained before it is necessary to make another brake applicaion is a guaranateed recipe for failure. There is no mention of Dynamic Brakes being used by either the original crew or the relief crew. The original crew, once the train was stopped in emergency DID NOT APPLY HAND BRAKES to any cars in the train.
I am not a Engineer, with that being said, I have worked with numerous engineers that are involved in handling trains on the worst main line grades on the former B&O's mountainous territories with grades in the same neighborhood as those that were involved in the runaway derailment in the TSB report. The knowledge I have gleaned from those engineers collective experiences lead me to believe what CP was doing in the instance was in reality 'worst practice procedures' and ended in the result such procedures would predict.
The current air brake system allows for switching cars with the brake cylinder air bled off and air pressure still in the air reservoir. The air pressure remaining in the reservoir could keep the automatic parking brake released for switching.
mvlandsw The current air brake system allows for switching cars with the brake cylinder air bled off and air pressure still in the air reservoir. The air pressure remaining in the reservoir could keep the automatic parking brake released for switching.
Blue Streak1 we can recharge from totally empty a SIT car in our yard for movement in our yard if we do need to move it in less than 2 minutes with just the air compressor mounted on the engine on an OTR truck. Even a standard air compressor could provide enough air to release the brakes if needed then put a check valve and manual shut off to allow the car to be moved. When it is moved pull the air off and reset the brakes.
blue streak 1 You should not forget that cars may sit for days, weeks, or even more than a month especially at locations that store cars waiting for the need of that special product. Think speciality plastic pellets. These are often shipper or receiver owned cars.
A short line near me stores upwards of 700 LP cars every summer when demand is down...
How long will the automatic brake hold if the train is off air?
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...
We have a trailer that was rear ended by a teenager in 08. The impact killed him and pushed the car in front of him under the trailer. Of part of the case was settled in 2010 but his family is still fighting in court the amount they're supposed to pay. So that trailer is still sitting out in the back of our yard once a year to keep it legal incase we need to move it for the case we go to it hook up drag it into the shop grease it inspect it replace tires if needed document everything done to the freaking screw and why and put it back.
tree68How long will the automatic brake hold if the train is off air?
It should also not compromise positive application, or positive release, of the individual manual brake at the wheel or lever, which is not an easy thing to assure.
There should also be an unambiguous, easily seen from well outside the 'fouling zone' between or at the ends of cars, that shows the automatic function has engaged. If I were doing it, the mechanism would also 'squawk' some kind of transponder, like an individualized ELT, that would identify each car that is locked or released.
The possible functionality of an Automatic Parking Brake (APB) was described in 2019 by Wabtec/GE here, on page 26 (page 24 as it appears by page folio):
http://rtcc.mrtd.gov.mn/upload/news_files/9d9565553c11860fa15124be708aaec3.pdf
To quote: "This device will not replace the conventional handbrake, but could serve as a secondary securement device. It would automatically engage to retain braking force by mechanically preventing the brake cylinder hollow rod from retracting in the event the brake cylinder pressure leaks off. The device engages when brake pressure drops below a certain point. Otherwise, the device remains disengaged, allowing normal operation of the brake cylinder."
Euclid Bruce, That is my understanding. Here is how I would explain it: Automatic parking brakes developed by Wabtec and New York Air Brake cannot inadvertently release due to leakage of air. Here is how they work: An emergency application of air brakes loads mechanical pressure to force the brake shoes against the wheels. Then a mechanical locking mechanism locks that air brake application force. Then if the air brake application air is released by any means, the mechanical lock will continue to maintain that stored brake force indefinitely unless the brake pipe of the air brake system is recharged. When the brake pipe is recharged, the mechanical lock will release. So the locking action of the mechanical lock is not dependent of air pressure to keep it in a locked position. It only depends on air pressure to release it.
What little I could find on these things is that they will set when brake pipe pressure drops below a certain point. Not necessarily through an emergency brake application. I saw one reference to 20 psi as the trigger point. That's the pressure level where passenger car brake equipment will go to emergency. Freight equipment does not have that feature.
One reference said the parking feature would release when brake pipe pressure reached about 45 psi. That's about the minimum pressure needed to transmit a pressure signal for freight brake equipment to go to emergency.
That it wouldn't replace hand brakes is true. When recharging from an emergency application on the side of a heavy grade, you would still need to apply enough hand brakes to hold the train until the brake system is fully charged.
It would also be necessary to manually release and disable the parking brake when switching without air connected. Which happens frequently in classification yards. Since it seems to operate off of brake pipe pressure, and not auxilary reservoir pressure.
Jeff
jeffhergertThat it wouldn't replace hand brakes is true. When recharging from an emergency application on the side of a heavy grade, you would still need to apply enough hand brakes to hold the train until the brake system is fully charged.
Seems like that would negate the whole concept as a solution for the runaway in question.
I read something about the possibility of being able to keep the automatic parking brake engaged even as the train line was recharged. (I checked both manufacturers but I couldn't find a lot of information easily.) I get the impression that it would be akin to setting up retainers. Someone has to walk along the train and manually override the automatic release function on a sufficient number of cars to hold it while recharging. Then once the system is recharged place them back into automatic mode. That might be the function of the pneumatic control module that is mentioned.
Possibly the pneumatic control module might also have an option for switching without air. To keep it from engaging when there is no air present in the brake pipe.
They could salve that by doing something like a pivot hooked up to what was the bleed rod. Pull it out for switching in for setting of the brakes. The challenges aren't impossible to overcome.
jeffhergertI read something about the possibility of being able to keep the automatic parking brake engaged even as the train line was recharged. (I checked both manufacturers but I couldn't find a lot of information easily.) I get the impression that it would be akin to setting up retainers. Someone has to walk along the train and manually override the automatic release function on a sufficient number of cars to hold it while recharging. Then once the system is recharged place them back into automatic mode. That might be the function of the pneumatic control module that is mentioned. Possibly the pneumatic control module might also have an option for switching without air. To keep it from engaging when there is no air present in the brake pipe. Jeff
In the runaway whose TSB Report has been linked into this thread. At the time the train began its roll it had 75% of its cars with the Retainer Valve set to the high pressure position by the Conductor of the original crew. These were set after the Emergency Brake Application done by the original engineer to stop the train when he detected it moving faster than instructions for the territory allowed.
BaltACDIn the runaway whose TSB Report has been linked into this thread. At the time the train began its roll it had 75% of its cars with the Retainer Valve set to the high pressure position by the Conductor of the original crew. These were set after the Emergency Brake Application done by the original engineer to stop the train when he detected it moving faster than instructions for the territory allowed.
Euclid BaltACD In the runaway whose TSB Report has been linked into this thread. At the time the train began its roll it had 75% of its cars with the Retainer Valve set to the high pressure position by the Conductor of the original crew. These were set after the Emergency Brake Application done by the original engineer to stop the train when he detected it moving faster than instructions for the territory allowed. As I recall, it was the replacement crew that had a meeting and decided to make the brake recovery by setting retainers rather than setting handbrakes. The first crew had made an emergency application to stop the train. That original emergency application continued to hold for some time, and was holding while the replacement crew was meeting to decide on the method of recovery. I don’t recall how far they got into the setting of retainers. But as the replacement engineer and brakeman were waiting on the engine while the conductor was out working the train, the original emergency application released and the train began to roll away. Had the replacement crew decided to set handbrakes, there is a good chance that the train would have remained secure. But the brake cylinder packing cups were leaking. This caused the emergency application n to leak off; and it would also have caused the setting of retainers to have had no effect. So the core problem was cylinder packing cups being too old, in weather that was too cold. They lost their ability to make a seal under those conditions.
BaltACD In the runaway whose TSB Report has been linked into this thread. At the time the train began its roll it had 75% of its cars with the Retainer Valve set to the high pressure position by the Conductor of the original crew. These were set after the Emergency Brake Application done by the original engineer to stop the train when he detected it moving faster than instructions for the territory allowed.
In reading the TSB report - the train started moving 32 minutes after the Relief Crew boarded the train. The Relief Crew was waiting of MofW that was doing snow clearance ahead of the train to report clear of the train. Retainers were set by the original crew, who would not have working time left by the time the retainers were set, thus the Relief Crew was ordered. Both crews had talked to the Trainmaster about the procedures the Trainmaster wanted used to move the train. The original crew talked to him by telephone/radio and the Relief crew talked to him in person at their on duty point.
My experiences on the mountain territory that I have supervised lead me to feel that 'retainers/release/recharge' is a very risky procedure to have a train recharge its brake trainline on a descending grade. Secure the train with HAND BRAKES and then go about recharging it. After the trainline is fully recharged, make a service application of the brakes and then begin releasing hand brakes - retainers can be set if desired. When the Conductor returns to the head end the train can proceed with brakes available to control speed.
In my opinion [note: as a non-PE and a non-railroader] the TSB 'engineers' and to some wider extent the Canadian engineering community associated with the reported system don't really appreciate what a parking-brake system for this purpose has to involve.
(1) It has to REPLACE the tying down of x large number of cars with manual handbrakes...
(2) When engaged, it has to completely SUBSTITUTE for the train's worth of applied manual securement.
(3) It must do this effectively 'in perpetuity', until consciously and non-accidentally released by a nontrivial action by whoever is monitoring or in control of the air brake system
(4) It must not be released unless and until the air-brake system is fully recharged, functional, and ready to be applied to correctly control the train. (This applies also to having dynamic brakes ready to act, if possible from zero axle rpm)
Some cockamamie system that relies on line pressures in a one-pipe system, or worse, having to 'notch' with pressure impulses, may be cute in terms of adding something to a pressure-maintaining system, but as Jeff notes pretty cogently you wouldn't want that sort of action on the precise train and conditions in the Field wreck. And as I think Zug noted a few years ago, all the then-current parking brakes (for locomotives) that actually worked were motored on and off... I remember the issues with the 'parking brake' on the GE at Lac Megantic and shudder at the idea that would ever be considered part of train securement.
What this might involve is a kind of incremental 'stalking horse; to modular ECP adoption. A motorized parking brake will need a battery, which will need a charging system and some sort of 'trainlined' monitoring and control to make sure all the little devices are on, off, or deflicted. All these could be rather easily provided by the 220V through harness used to make one-pipe cars compatible with an ECP installation, something comparably cheap to install and keep maintained, and easy to field-test and field-repair.
Then, if you have individual cars that have had the "optional ECP" equipment installed at their brake system, which cost mere thousands per car years ago and less if mandated or government-subsidized, full ECP involves only a few field conversions on the harness connections in addition to the connections at the valves, which is supposed to be likewise easy in the field and involve only a few minutes' time...
OvermodOvermod wrote the following post 18 hours ago: In my opinion [note: as a non-PE and a non-railroader] the TSB 'engineers' and to some wider extent the Canadian engineering community associated with the reported system don't really appreciate what a parking-brake system for this purpose has to involve. (1) It has to REPLACE the tying down of x large number of cars with manual handbrakes... (2) When engaged, it has to completely SUBSTITUTE for the train's worth of applied manual securement. (3) It must do this effectively 'in perpetuity', until consciously and non-accidentally released by a nontrivial action by whoever is monitoring or in control of the air brake system (4) It must not be released unless and until the air-brake system is fully recharged, functional, and ready to be applied to correctly control the train. (This applies also to having dynamic brakes ready to act, if possible from zero axle rpm)
I think part of what unnerves me is that they're proposing a mechanical lock on an applied foundation, and trusting that if the air behind the set leaks off, the foundation won't move. And if the foundation is not fully-enough applied the lock will not engage. There are maintenance and slack assumptions in there that I don't fully trust.
Remember that the system has to work effectively and reliably a decade from now, on cars like those Bob Smith has repeatedly described...
After reading the PDF of the 2 systems in it the Wabtec has the best possible design. Allows for release for air less switching and maintenance with a simple flip of a lever yet when tripped after an emergency stop can't even be released by the crew until they have a minimum of 45 psi in the airline. This is 25 psi more than a retainer has at high settings and the way it is designed can be retrofitted into all existing cars fairly easily.
Our community is FREE to join. To participate you must either login or register for an account.