Re: Brake Pipe Air
Date: 04-19-2017 - 09:54
There are too many other factors to figure. Length of the train, BP pressure, type of brake valve on car, air compressor, main reservoir pressure, etc.
Just take the compressor:
Air compressed to 1/10 of original volume (saturated) Temperature 350 degrees at 130-140 PSI. Then you have to figure No. 1 Main Res. & No. 2 Main Res., after coolers
The feed valve is only .018.
A standard car has a total of 1,000 cu. in. of piping.
Charging time for a "Dry Car" (mild temp, minimum leakage) is 7 minutes. 50 cars is 16", 100 cars 33".
It only takes 1.6 lbs change to start a car to release or to set up. For cars 65 feet or longer they need a A-1 Reduction Relay valve to compensate for increased brake pipe volume.
This is for one car.
Pressures for a 90 lb brake pipe:
Brk Pipe Emer Res Aux Res Brk Cyl.
Running 90 90 90 0
Full Service 64 90 64 64
Emergency 0 77 77 77
As you can see, there is not a rubber stamp for brake pipe air.
The problem of outside temp all depends on a bunch of other variables too. If it is way below freezing, it affects the ability of air to move back and forth in the BP. The railroads used to pour alcohol into the glad hands every 5 or 10 cars and that would get rid of some of the moisture. A lot of carriers stopped that because it would dry up all the seals and cause problems later on. But I have seen it many times where it could take you hours and hours to be able to make your air test.