Bottling the air

[NW Mailing List]

My replies date to operations before ABDW.

With ABDW, if you turned the angle cock before the sir stopped flowing 
toward the engine, It would surge back through the train like water 
sloshing. It only took @ 2.4 pounds of air pressure increase to trip the 
system in each car so that the emergency res would flood its air into 
the train line and continue to build pressure and continue the release.

     WJPowers


On 10/31/2018 2:52 PM, NW Mailing List via NW-Mailing-List wrote:
> The ABDW brake valve made its appearance in the late 1960s.
> It was very sensitive to the slightest change in brake pipe
> pressure.  Instructions had been for the engineer to reduce
> brake pipe pressure to 30 lbs (?), afterward he would sound
> the whistle to notify the brakeman to uncouple.  The angle
> cocks were to be slowly closed, then the pin could be pulled.
> An empty train from Lamberts Point had left with only 90
> mtys with instructions to stop at Petersburg and pick up an
> additional 90 at Broadway Yard.  On the slope from Poe
> to Petersburg, the train stopped and the brakeman slammed
> the angle cocks shut before the air was properly reduced.
> As the head end crew coupled to the pick up, the rear of the
> train passed.  The conductor had thought the head end
> crew had made a record-setting pick up, but as the cab
> passed, the head end crew signaled that he was in command
> of a run-away.  The sensitivity of the ABDW valve had released
> the "bottled" air when the brakeman slammed the angle cocks
> shut  It took a few minutes for the brakes to release.
> Harry Bundy
>
>
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