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...
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?
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?
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.
Never too old to have a happy childhood!
I found a decent Burlington Northern video about train air brakes. 20 mins. long.
https://www.youtube.com/watch?v=K4n3W1GN1pA
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?
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.
Greetings from Alberta
-an Articulate Malcontent
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.
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