Pumping up the air!

[dave1905]

Gary, that is not a simple question to answer. we allowed 8 minutes for the cars to charge before we did a brake test. 1-8 cars completely drained should charge in this time, then allow a minute per car for more then 8.
You could kick a car by either "bottling " the air, which means close both angle cocks without the brakes applied, or by bleeding the system completely. Some plants where cars are spotted will bleed the air so they can move the car with other means. It is when they are bled that it takes so long to charge. All cars are drained in the yards for humping and many when flat switching, thus the ground lines are used to charge the train lines in newly made trains waiting for crews and motive power. This saves time so the crew can couple into the train, pump off the brakes and do their brake test before leaving the yard. 100 per cent of the brakes have to work before leaving a terminal. There are different tests required for switching operations out and about.
Charlie

On many roads "bottling the air" is against the rules because with modern air brakes, bottling the air can inadvertantly cause all the brakes to release on a cut of cars. On modern air brakes if the pressure in the line is a certain amount above the reservior pressure the valve will think the brakes are released. If you set the brakes and then turn the angle cock on the detached portion it can set up a pressure wave in the train line. If one of the brake valves thinks the pressure wave is an increase in brake line presure it dumps air from the reservoirs into the train line to speed up the charging. That increases the pressure causing the next car to do the same. End result all the cars release the brakes and the bottle portion rolls off.