BaltACD Paul of Covington I remember when I first read about that, I found it hard to believe. It seemed incredibly dangerous. It seems like a minor fault can release all the brakes. If you sense that this is happening, is it likely that you can dump the air and have enough air in the reservoirs to stop the train? Have any of you engineers had this happen? (edit) I realized after I wrote the above that you were talking about the air being bottled, but if it happens when you are moving (say downhill) with a service application on, won't the same problem exist? Engines of recent vintage (last half century) have a Pressure Mainting feature that will keep the trainline pressure at the pressure set by the Engineer when he made his brake line reduction to apply the brakes. In the bottled air 'release' the only air pressure entered into the trainline comes from the defective brake valve's reservior, which changes the pressure in the trainline.
Paul of Covington I remember when I first read about that, I found it hard to believe. It seemed incredibly dangerous. It seems like a minor fault can release all the brakes. If you sense that this is happening, is it likely that you can dump the air and have enough air in the reservoirs to stop the train? Have any of you engineers had this happen? (edit) I realized after I wrote the above that you were talking about the air being bottled, but if it happens when you are moving (say downhill) with a service application on, won't the same problem exist?
(edit) I realized after I wrote the above that you were talking about the air being bottled, but if it happens when you are moving (say downhill) with a service application on, won't the same problem exist?
Engines of recent vintage (last half century) have a Pressure Mainting feature that will keep the trainline pressure at the pressure set by the Engineer when he made his brake line reduction to apply the brakes.
In the bottled air 'release' the only air pressure entered into the trainline comes from the defective brake valve's reservior, which changes the pressure in the trainline.
Paul makes a good point. Unintentional releases can indeed be a problem when riding a automatic brake application down a long, steep grade.
I recall one particular unintentional release that I suspect was caused by a single car leaking off, releasing itself, and triggering the chain reaction. I felt the train start to accelerate drastically for no apparent reason and immediately took more air, which got us to the bottom of the hill. This was on a 3% grade with a loaded coal train.
Another way an unintentional release can happen is if the slack is bunched up hard, and some minor brake pipe air leaks get shut by this action. The locomotive brake valve's pressure maintaining feature will have been adding air into the brake pipe to compensate for those leaks, and sometimes it doesn't react quickly enough when the leaks disappear. If it keeps adding air for just a bit too long it can cause the brake pipe pressure to rise enough to trigger a release, and then the chain reaction takes over.
Besides the surprise acceleration, signs of an unitentional release starting are a sharp increase in airflow and/or a rise on the tail end pressure gauge.
Greetings from Alberta
-an Articulate Malcontent
BaltACD adkrr64 I know sometimes cuts of cars are left on "shop" air (may have the wrong term) - to keep the brake system charged and minimize the amount of time spent by crews picking up those cars. In such a case, are those left standing with a brake application (brake pipe less than 90 PSI) or in release, with just hand brakes holding the cut? Cuts that are on track that are supplied with 'Yard Air' will be secured on the track with hand brakes - the number will most likely be specified in the TTSI applicable to the territory. Yard Air is used by Car Department personnel in performing a Class 1 brake test on the cut of car - observing both the application and release of the brakes on all the cars in the cut, and leaving a 'Air Slip' detailing who performed the test and the time the test was performed, this is done so the crew picking up the cars won't have to expend the necessary time to perform the Class 1 Brake Test themselves. On CSX there is a computer application that permits searching for 'Air Slips' where the physical document has become lost. By FRA Rules, if a cut of cars is not 'on air' for more than 4 hours, the cut must again get a Class 1 Air Test after air is restored to the cut.
adkrr64 I know sometimes cuts of cars are left on "shop" air (may have the wrong term) - to keep the brake system charged and minimize the amount of time spent by crews picking up those cars. In such a case, are those left standing with a brake application (brake pipe less than 90 PSI) or in release, with just hand brakes holding the cut?
Cuts that are on track that are supplied with 'Yard Air' will be secured on the track with hand brakes - the number will most likely be specified in the TTSI applicable to the territory.
Yard Air is used by Car Department personnel in performing a Class 1 brake test on the cut of car - observing both the application and release of the brakes on all the cars in the cut, and leaving a 'Air Slip' detailing who performed the test and the time the test was performed, this is done so the crew picking up the cars won't have to expend the necessary time to perform the Class 1 Brake Test themselves. On CSX there is a computer application that permits searching for 'Air Slips' where the physical document has become lost.
By FRA Rules, if a cut of cars is not 'on air' for more than 4 hours, the cut must again get a Class 1 Air Test after air is restored to the cut.
In Canada the time limit is 24 hours. We also have a computer system that keeps track of air tests. Those records must be retained for 30 days per the Canadian regulations.
I've called the RTC Mechanical number on numerous occasions when a hard copy of the 'Air Slip' (Train Brake Status Report, or TBSR in Canadianese) is not available.
We have some yards that are bowled, that is the centre of the yard is the bottom of a hill, sloping upward in both directions. Such a design makes it physically impossible for cars to roll away via gravity alone. We are allowed to leave the air bottled without handbrakes applied in certain locations like this, and in at least one yard we are allowed to kick cars into a clear track without anyone riding the handbrake, as long as the cars are released at 3 mph or less.
I found a decent Burlington Northern video about train air brakes. 20 mins. long.
https://www.youtube.com/watch?v=K4n3W1GN1pA
adkrr64I know sometimes cuts of cars are left on "shop" air (may have the wrong term) - to keep the brake system charged and minimize the amount of time spent by crews picking up those cars. In such a case, are those left standing with a brake application (brake pipe less than 90 PSI) or in release, with just hand brakes holding the cut?
Never too old to have a happy childhood!
I know sometimes cuts of cars are left on "shop" air (may have the wrong term) - to keep the brake system charged and minimize the amount of time spent by crews picking up those cars. In such a case, are those left standing with a brake application (brake pipe less than 90 PSI) or in release, with just hand brakes holding the cut?
Lithonia Operator tree68 The air could (and probably would be) bottled with a set on the train, and this is where the problem lies. Larry, I think I've pretty much got it, but could you explain the above part more? Sorry to be so numb...
tree68 The air could (and probably would be) bottled with a set on the train, and this is where the problem lies.
Larry, I think I've pretty much got it, but could you explain the above part more?
Sorry to be so numb...
When stopping for whatever reason where the train was to be broken apart, the engineer would usually have a set on the train - ie, the pressure in the brake pipe would have been reduced, causing the brakes on the cars to set. Let's say he/she made a ten pound reduction on the pipe to stop the train. The pressure in the brake pipe would now be 80 PSI (assuming a normal 90 PSI brake pipe).
IF the crewmember breaking the coupling were to bottle the air on the standing portion of the train, the standing portion would have that 80 PSI "bottled up."
That's when the leaking valves, etc, come into play.
As has been mentioned, bottling the air is both illegal and unsafe. I framed my comment as if those considerations had been ignored.
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...
tree68The air could (and probably would be) bottled with a set on the train, and this is where the problem lies.
Sorry to be so numb.
OK, I see the difference. The maintaining feature will bleed off the air that was added by the defective valve. Thanks. I guess it's not as bad as I thought.
_____________
"A stranger's just a friend you ain't met yet." --- Dave Gardner
SD70DudeThe "Quick Release" feature of modern car control valves is the main cause of unintentional releases when the air is bottled. This feature works by pouring air from the car's emergency reservoir back into the brake pipe when the triple valve moves to the release position. Let's say we have bottled the air on a train, and one car has a air leak on the control valve or auxiliary reservoir pipe. Once the auxiliary reservoir pressure drops below the brake pipe pressure the triple valve will move to the release position, and the emergency reservoir air (still at a full charge of 90 PSI) will be allowed into the brake pipe, raising the brake pipe pressure at that car. Once this rise in pressure reaches the next car it will also release, and this process will continue until most, if not all the cars are released.
I remember when I first read about that, I found it hard to believe. It seemed incredibly dangerous. It seems like a minor fault can release all the brakes. If you sense that this is happening, is it likely that you can dump the air and have enough air in the reservoirs to stop the train? Have any of you engineers had this happen?
cx500 I understood one cause was closing the angle cock while the train line was still venting, which could cause enough of a "bounceback" in the air column to fool the valves into thinking it was a release. I may be wrong.
I understood one cause was closing the angle cock while the train line was still venting, which could cause enough of a "bounceback" in the air column to fool the valves into thinking it was a release. I may be wrong.
That's right. When we 'cut and vent' the Engineer has to wait for the exhaust to cease before telling the Conductor to close both angle cocks, uncouple the locomotive, and then slowly open the angle cock on the train.
The "Quick Release" feature of modern car control valves is the main cause of unintentional releases when the air is bottled. This feature works by pouring air from the car's emergency reservoir back into the brake pipe when the triple valve moves to the release position.
Let's say we have bottled the air on a train, and one car has a air leak on the control valve or auxiliary reservoir pipe. Once the auxiliary reservoir pressure drops below the brake pipe pressure the triple valve will move to the release position, and the emergency reservoir air (still at a full charge of 90 PSI) will be allowed into the brake pipe, raising the brake pipe pressure at that car. Once this rise in pressure reaches the next car it will also release, and this process will continue until most, if not all the cars are released.
Of course, the train may roll away and derail before every single car is released.
BaltACDIf you cut away from a train, vent the trainline to atmosphere!
Well, you should have proper handbrakes witha proper handbrake test, so the air shoudn't matter.
It's been fun. But it isn't much fun anymore. Signing off for now.
The opinions expressed here represent my own and not those of my employer, any other railroad, company, or person.t fun any
Lithonia Operator BaltACD The couple of minutes 'saved' when the air is bottled on a cut of cars does not come close to equaling the risk of the cut releasing the air and rolling away. If the cut released the air, wouldn't that make the brakes apply? And keep the cut from moving? I thought the problem with bottled air is that it keeps the brakes in the released position. So if enough hand brakes aren't set, there ... goes ... your ... train ...
BaltACD The couple of minutes 'saved' when the air is bottled on a cut of cars does not come close to equaling the risk of the cut releasing the air and rolling away.
If the cut released the air, wouldn't that make the brakes apply? And keep the cut from moving?
I thought the problem with bottled air is that it keeps the brakes in the released position. So if enough hand brakes aren't set, there ... goes ... your ... train ...
When brakes are applied, air is taken out of the train line and thus signaling the brake valve for the higher pressure in the reservoir to apply the pistion in the brake cylinder. If the air is bottled you now have a captive trainline - IF a defective brake valve for whatever the reason vents either its service or emergency brake reservoirs into the train line - the train line pressure increases thus signaling all the brake valves in the trainline to release their brakes. With the brakes having been commanded to release - away rolls the train.
If you cut away from a train, vent the trainline to atmosphere!
mvlandswIf the wheels were to slide the wheel slip system would operate to give warning and cut off the dynamics. You would get no such warning using just the independent brake.
Except for the unmistakable ssssssssssss.... from under the cab.
For us, we are prohibited from using the dynamic and indep together. It's a trigger that will get emailed to whatever roadforemen are left. I've done plenty of shifting with single brakeshoe engines - some times you have to be the mean engineer and tell Mr. Conductor to give you a couple cars of air.
Paul of Covington I remember reading about this incident in TRAINS, and I've wondered ever since why the engineer would consider putting the engine in dynamic braking. It's my understanding that dynamics are ineffective at low speed (at least in DC locomotives), and since he was engaged in yard work, I wouldn't have thought that he would consider it.
I remember reading about this incident in TRAINS, and I've wondered ever since why the engineer would consider putting the engine in dynamic braking. It's my understanding that dynamics are ineffective at low speed (at least in DC locomotives), and since he was engaged in yard work, I wouldn't have thought that he would consider it.
If the wheels were to slide the wheel slip system would operate to give warning and cut off the dynamics. You would get no such warning using just the independent brake.
Mark Vinski
Lithonia OperatorI thought the problem with bottled air is that it keeps the brakes in the released position. So if enough hand brakes aren't set, there ... goes ... your ... train ...
The air could (and probably would be) bottled with a set on the train, and this is where the problem lies.
If a leak allows air back into the brake pipe the increase in pressure in the bottled line will likely cause the brakes on the cars to release (as noted in the primer).
On top of that, modern brakes are designed so that air from the emergency reservoir is also fed into the brake pipe, speeding the release of the brakes.
IF you're going to not set hand brakes, you're better off not bottling the air, as the emergency application is going to hold for a while, anyhow.
BaltACDThe couple of minutes 'saved' when the air is bottled on a cut of cars does not come close to equaling the risk of the cut releasing the air and rolling away.
Lithonia OperatorSo, say a train comes off the road, into a yard. The power unhooks, heads off to the engine house. The cut now has air in the reservoirs and in the cylinders, the amount of which a result of how much braking and re-charging had been done on the road. So, do the car-knockers now walk the train and 1) check for defects, and 2) bleed all air from the cylinders and reservoirs? Does a single valve bleed both the car's cylinder and reservoir? Is there any way to bleed more than one car at a time? Is there a situation whereby the cylinders get bled, but some air is retained in the reservoirs? If so, why would one do that? Did the train crew tie on some hand brakes on the cut before they disconnected? Is "bottling air"which I know is against the rules, a way for an engine crew to disconnect from the cut and, say, go pick up a car in a stub track, then couple back up up, but not have to use all time pumping the train back up? Is that why you'd bottle air. Please answer like you're teaching a sixth-grader!
So, do the car-knockers now walk the train and 1) check for defects, and 2) bleed all air from the cylinders and reservoirs?
Does a single valve bleed both the car's cylinder and reservoir? Is there any way to bleed more than one car at a time? Is there a situation whereby the cylinders get bled, but some air is retained in the reservoirs? If so, why would one do that?
Did the train crew tie on some hand brakes on the cut before they disconnected?
Is "bottling air"which I know is against the rules, a way for an engine crew to disconnect from the cut and, say, go pick up a car in a stub track, then couple back up up, but not have to use all time pumping the train back up? Is that why you'd bottle air.
Please answer like you're teaching a sixth-grader!
If the terminal is a Hump Yard and the arriving train is to be switched over the hump as its 'next' move, the car inspectors will perform a arrival inspection of all cars and bleed the air off the reservoirs so the cars can be 'free wheeling' over the hump. The single bleed rod can be activated from either side of the car. The inspection also identifies defects that may cause car(s) to be switched for Shop Track attention. Each Hump Yard has its own set of TTSI on how the first cars switched into a Bowl Track are to be handled - if hand brakes are to be used, if skates are to be used, if the configuration of the Bowl Track percludes a free rolling car from exiting the track (many Bowl Track are built with the configuration of a bowl - higher on both ends of the track than at the middle of the tracks length.
TTSI for the Terminal will govern the application of hand brakes for arriving trains; not all Terminals have the same TTSI because of the differing 'lay of the land' for each terminal.
The couple of minutes 'saved' when the air is bottled on a cut of cars does not come close to equaling the risk of the cut releasing the air and rolling away. A simple risk/reward equation. Anecdote - CSX coal train moving from Brunswick, MD to the Pepco Morgantown Power Plant via Benning Yard in the District of Columbia. Trains arriving Benning from Brunswick are moving West to East, trains departing Benning for Morgantown require the EOT and Power to be in the opposite positions that they arrived from Brunswick. Crew from Brunswick brought a train into Benning, made a reduction on the train an bottled the air as they went to the rear of their train to get the EOT and bring it back to where the power HAD been coupled. Before they could get the EOT and return to where they were previously coupled - the train ran away onto the Anacostia River Bridge (that was undergoing reconstruction accound steel eating bacteria in the river had damaged the original bridge) the bridge collapsed under the weight of the cars and about 19 cars ended up in the river. Risk/reward.
Lithonia OperatorSo, do the car-knockers now walk the train and 1) check for defects, and 2) bleed all air from the cylinders and reservoirs?
Not something I have any experience with - in fact, we can't move passenger cars unless they are on air.
Lithonia OperatorDid the train crew tie on some hand brakes on the cut before they disconnected?
Lithonia OperatorIs "bottling air"which I know is against the rules, a way for an engine crew to disconnect from the cut and, say, go pick up a car in a stub track, then couple back up up, but not have to use all time pumping the train back up? Is that why you'd bottle air.
Don't get caught! While a crew could use that practice, you won't find it in the field. The dispatcher has the delay planned in his/her plan. Doing so for an "early quit" might result in a permanent quit...
tree68 Lithonia Operator Yes or No: when the hose gets disconnected from the engine, it also dumps all the air from the reservoirs in the train? No. Key phrase there is "all the air." With an emergency application (brake pipe pressure suddenly goes to zero), air from the reservoirs is routed to the brake cylinders. The pressure in the reservoirs will only drop to a certain point, that being where the pressure in the reservoir equalizes with that in the brake cylinders. That's what holds the brakes in application. There will still be pressure in the reservoirs, hence my "no" answer. As you saw in the primer, when air pressure is restored to the brake line, the reservoirs recharge and the pressure in the brake cylinders is released to the atmosphere, releasing the brakes. But I digress. In the case of work in a yard, it's necessary to release all pressure (bleed off) from the reservoirs as well, so there's no way for the brakes to apply. This is why it takes so long to completely charge a train - if all the cars have been bled off then all the reservoirs have to be refilled. That can be a lot of air. If the brake system air on a car is good and tight, an emergency application such as will occur when a car is set out and the air is thus dumped may hold for quite a while. A "leaky" car may only hold that application for a short while. Hopefully the mud has settled a little...
Lithonia Operator Yes or No: when the hose gets disconnected from the engine, it also dumps all the air from the reservoirs in the train?
No. Key phrase there is "all the air."
With an emergency application (brake pipe pressure suddenly goes to zero), air from the reservoirs is routed to the brake cylinders. The pressure in the reservoirs will only drop to a certain point, that being where the pressure in the reservoir equalizes with that in the brake cylinders. That's what holds the brakes in application. There will still be pressure in the reservoirs, hence my "no" answer.
As you saw in the primer, when air pressure is restored to the brake line, the reservoirs recharge and the pressure in the brake cylinders is released to the atmosphere, releasing the brakes. But I digress.
In the case of work in a yard, it's necessary to release all pressure (bleed off) from the reservoirs as well, so there's no way for the brakes to apply. This is why it takes so long to completely charge a train - if all the cars have been bled off then all the reservoirs have to be refilled. That can be a lot of air.
If the brake system air on a car is good and tight, an emergency application such as will occur when a car is set out and the air is thus dumped may hold for quite a while. A "leaky" car may only hold that application for a short while.
Hopefully the mud has settled a little...
Thanks, Larry.
So, say a train comes off the road, into a yard. The power unhooks, heads off to the engine house. The cut now has air in the reservoirs and in the cylinders, the amount of which a result of how much braking and re-charging had been done on the road.
zugmann adkrr64 Convicted One But why leave the throttle engaged? From my understading, he thought he had applied the dynamic brake lever and instead applied the throttle lever. Plausible for certain types of control stands, especially if one is in a panic. Forgot about that. Engine had the power/dynamic selector switch.
adkrr64 Convicted One But why leave the throttle engaged? From my understading, he thought he had applied the dynamic brake lever and instead applied the throttle lever. Plausible for certain types of control stands, especially if one is in a panic.
Convicted One But why leave the throttle engaged?
But why leave the throttle engaged?
Forgot about that. Engine had the power/dynamic selector switch.
Yes.
Here is a control stand with a single controller handle and the selector switch, which determines whether the controller handle will engage traction power or dynamic braking.
https://en.m.wikipedia.org/wiki/File:UP_Centennial_control_stand.jpg
Here is a control stand with separate throttle and dynamic handles:
https://www.discoverlivesteam.com/discoverforsale/forsale/8_Flanders/IMG_8243.jpeg
Lithonia OperatorYes or No: when the hose gets disconnected from the engine, it also dumps all the air from the reservoirs in the train?
Yes or No: when the hose gets disconnected from the engine, it also dumps all the air from the reservoirs in the train?
Only if there were air in the reservoirs to begin with. This was a yard move, and the cars probably had all been bled off, hence were just that much rolling weight.Back when we were tying onto a track in the classification yard to couple and pull it, we'd make the hoses and cut the air in on the first three or four (or so) cars, to give the poor overused Geep a little extra stopping power.
Carl
Railroader Emeritus (practiced railroading for 46 years--and in 2010 I finally got it right!)
CAACSCOCOM--I don't want to behave improperly, so I just won't behave at all. (SM)
tree68 Lithonia Operator Are you telling me that when the air rushes out with the big pfffffffft, that's not just air from the brake pipe, but rather it's also from all the reservoirs? A good read on this would be Al Krug's primer on air brakes: http://www.railway-technical.com/trains/rolling-stock-index-l/train-equipment/brakes/north-american-freight.html
Lithonia Operator Are you telling me that when the air rushes out with the big pfffffffft, that's not just air from the brake pipe, but rather it's also from all the reservoirs?
A good read on this would be Al Krug's primer on air brakes:
http://www.railway-technical.com/trains/rolling-stock-index-l/train-equipment/brakes/north-american-freight.html
That's exactly the article I read last night! I must have misunderstood.
In recent memory, CSX had an issue in north central Ohio with a similar scenario with an engine and GP30 slug going for a ride.
Lithonia OperatorAre you telling me that when the air rushes out with the big pfffffffft, that's not just air from the brake pipe, but rather it's also from all the reservoirs?
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