07-08-2013, 09:08 PM
It doesn't matter why the air leaked off and the train ran away. The question that needs to be solved is why there were not enough hand brakes applied to hold the train even without air. The problem with relying on a locomotive to supply air is what could have happened here, and the air became "bottled" when the engine shut down, and the pressures equalized and the brakes all released. If the cars were placed in "emergency" (all the air removed from the train line and the line left open) then the reservoirs in every car would have to bleed off, which is highly unlikely in that short a period. There are two ways to move cars by kicking. one is to bleed all the air out of the car, and the other is to Bottle it.
To bottle air you pump the trainline up and release the brakes, then you close BOTH anglecocks on the car, which keeps the brakes released. If there are no leaks in the trainline on the car it will move until you release the air from the train line. The common pressure in a freight train trainline is 90 PSI. to apply the brakes the engineer applies a reduction to the train line and this applies the brakes. when he releases the brake, the trainline returns to 90 PSI and the brakes start to release. There is a feed line to the main reservoir on each car and the trainline pressure replenishes the air lost from the reservoir when the brakes were applied. This takes a short period of time. When an emergency application occurs all of the air from the trainline is exhausted and the brakes apply at their fullest force.
You have to be very careful when applying brakes especially on a grade. Unlike a truck where you can pump the brakes (a certain amount) (spring loaded brake) You will run the reservoirs out of air by doing this on a train, and then you have a run away if your locomotives can't handle it with the dynamic brakes. You make a reduction and live with it, and only release when it is safe. With dynamic braking today the air brakes are secondary though the airbrake is still the primary braking system. The dynamic brakes are why you see helpers on trains going downgrade.
I spent 10 years listening to a gentleman that became a close friend that was one of the top air brake men with the FRA. We discussed many things about air brakes and I asked many questions about rules I deemed obsolete. The single car brake test that is required today was one of the best rule changes I saw enacted while I was with the railroad.
I know there are other engineers on this board that can help clarify what I am saying, but to put if bluntly, if the train crew did their job correctly, there is something going on here that needs attention.
It is a true crime that so many people have lost their lives.
These are all my own opinion, take them for what they are worth.
Charlie
To bottle air you pump the trainline up and release the brakes, then you close BOTH anglecocks on the car, which keeps the brakes released. If there are no leaks in the trainline on the car it will move until you release the air from the train line. The common pressure in a freight train trainline is 90 PSI. to apply the brakes the engineer applies a reduction to the train line and this applies the brakes. when he releases the brake, the trainline returns to 90 PSI and the brakes start to release. There is a feed line to the main reservoir on each car and the trainline pressure replenishes the air lost from the reservoir when the brakes were applied. This takes a short period of time. When an emergency application occurs all of the air from the trainline is exhausted and the brakes apply at their fullest force.
You have to be very careful when applying brakes especially on a grade. Unlike a truck where you can pump the brakes (a certain amount) (spring loaded brake) You will run the reservoirs out of air by doing this on a train, and then you have a run away if your locomotives can't handle it with the dynamic brakes. You make a reduction and live with it, and only release when it is safe. With dynamic braking today the air brakes are secondary though the airbrake is still the primary braking system. The dynamic brakes are why you see helpers on trains going downgrade.
I spent 10 years listening to a gentleman that became a close friend that was one of the top air brake men with the FRA. We discussed many things about air brakes and I asked many questions about rules I deemed obsolete. The single car brake test that is required today was one of the best rule changes I saw enacted while I was with the railroad.
I know there are other engineers on this board that can help clarify what I am saying, but to put if bluntly, if the train crew did their job correctly, there is something going on here that needs attention.
It is a true crime that so many people have lost their lives.
These are all my own opinion, take them for what they are worth.
Charlie