i have read that this system works on vacuum but actually how any why vacuum is needed in the trains and how it is linked with the brakes?
The Indian trains are powered with Air Brakes and Vacuum Brakes. Air Brakes: The compressed air is used for acquiring brake application. The brake pipe and feed pipe run throughout the time of the size of the instructor. Brake pipe and feed pipe on consecutive coaches interior the prepare are coupled to a minimum of one yet another by utilizing ability of respective hose couplings to type a non-provide up air passage from the locomotive to the rear end of the prepare. The compressed air is provided to the brake pipe and feed pipe from the locomotive. The value of braking tension will enhance in steps with the corresponding relief in brake pipe tension and vice - versa. Vacuum Brakes: The vacuum brake equipment derives its brake tension from the atmospheric tension appearing on the decrease edge of the piston interior the vacuum brake cylinder mutually as a vacuum is maintained above the piston. The prepare pipe runs throughout the time of the size of the instructor and related with consecutive coaches by utilizing hose coupling. The vacuum is created interior the prepare pipe and the vacuum cylinder by utilizing the ejector or exhauster fixed on the locomotive.
Damocles is correct, it is positive air pressure, not a vacuum. It's much easier to make a hose that withstands outward pressure as opposed to vacuum, which tends to collapse the hose. The air pressure keeps the brakes off, and when the pressure is released, the brakes go on. It's a safety feature, so if a hose is broken the brakes are applied automatically. It was invented by Westinghouse, after a string of RR accidents. .
There are hoses between the cars. Air pressure in these hoses keeps the brakes from being applied. If a train wants to brake, then the air is pumped out of these hoses. Here's the thing. It's a fail safe. If a train car somehow separates from the one in front of it, this hose is going to pop off and the car will loose air pressure and the brakes will kick in. If the car separates from the rest of the train, it will stop. Of course, spring a leak in one of those hoses and the breaks kick in too. :-) Look at train cars next time you see them and you'll see this big metal coupler, but also a couple of hoses connecting the cars. I was under the impression that there is positive pressure in the hoses, pressure that would be lost if the hose separates. However, I suppose it could be a vacuum (negative pressure - i.e. less than one atomosphere of pressure) in the hose (i.e. air is pumped out of it). If that separated, air would rush into the hose too.
