Air Brake System In Trains Pdf
However, they are only used in an emergency, usually being triggered by the triple valve sensing a sudden drop in brake pipe pressure. An emergency application also results when the train line comes apart or otherwise fails, as all air will also be immediately vented to atmosphere. Main reservoir pipe pressure can also be used to supply air for auxiliary systems such as pneumatic door operators or air suspension. By compressed air desired force required for breaking the train is applied on block and train motion ceases. In addition to the traditional brake pipe, this enhancement adds the main reservoir pipe, which is continuously charged with air directly from the locomotive's main reservoir.
The operation of the air brake on each vehicle relies on the difference in pressure between one side of the triple valve piston and the other. Westinghouse soon improved the device by removing the poppet valve action, these three components became the piston valve, the slide valve, and the graduating valve. After he released the air from the system, the train rolled freely, but the remaining cars that had a charged system didn't have enough stopping power. The air brake system is undoubtedly one of the most enduring features of railway technology. The triple valve contains a slide valve which detects changes in the brake pipe pressure and rearranges the connections inside the valve accordingly.
The brake pipe is carried between adjacent vehicles through flexible hoses. The one-way valve allows air from the main reservoir pipe to top up the auxiliary reservoir.
The Westinghouse air brake system is very trustworthy, but not infallible. When the engine operator releases the brake, the locomotive brake valve portal to atmosphere is closed, allowing the train line to be recharged by the compressor of the locomotive. Often made of cast iron or some composition material, brake blocks are the main source of wear in the brake system and require regular inspection to see that they are changed when required. The main reservoir is where the locomotive's air compressor output is stored, and is ultimately the source of compressed air for all systems that use it. Most vehicles fitted with distributors or two-pipe systems can be operated in trains with simple one-pipe systems and triple valves, who classification of brain tumors pdf subject to the correct set-up during train formation.
At the same time, the connection at the bottom of the slide valve will allow any air pressure in the brake cylinder to escape through the exhaust port to atmosphere. Please help to improve this article by introducing more precise citations. Another solution to loss of brake pressure is the two-pipe system, fitted on most locomotive-hauled passenger stock and many freight wagons. For details, see Auxiliary Equipment.
It performs no control function but it is used to overcome the problem of critical loss of pressure in the auxiliary reservoirs on each car. The length of time will depend on the amount of air used for the previous application and the length of the train. Each axle was also equipped with anti-lock brake equipment. The feed groove allows brake pipe air pressure to enter the auxiliary reservoir and it will recharge it until its pressure is the same as that in the brake pipe. Distributors may also have a partial release facility, something not usually available with triple valves.
This valve is set to a specific operating pressure. This could easily cause a runaway train. However, the basic air brakes used on railways worldwide are remarkably compatible.
Electro-vacuum brakes have also been used with considerable success on South African electric multiple unit trains. Distributors with all these features will normally be provided on passenger trains or specialist high-speed freight vehicles. There are a number of safeguards that are usually taken to prevent this sort of accident happening.
This is the brake valve that was my introduction to train braking. The air brake can fail if one of the cocks where the pipes of each carriage are joined together is accidentally closed. The pressurized air comes from an air compressor in the locomotive and is sent from car to car by a train line made up of pipes beneath each car and hoses between cars. Auxiliary reservoir air now feeds through into the brake cylinder. Some air brake systems use emergency reservoirs.
The brake pipe pressure is reduced as air escapes. On an air braked train, the compressed air supply is used to provide power for certain other functions besides braking. This arrangement helps to reduce the above described pressure loss problems, and also reduces the time required for the brakes to release, since the brake pipe only has to recharge itself.
It has lasted from its initial introduction in to the present day and in some places, still hardly different from its Victorian origins. The car reservoirs recharge only when the brake pipe pressure is higher than the reservoir pressure, and that the car reservoir pressure will rise only to the point of thermodynamic equilibrium. It can only be used to provide a partial application. The material used for braking is normally in the form of a block or pad.
The conversion is usually done by applying a contact material to the rotating wheels or to discs attached to the axles. The flow of air into and out of the auxiliary reservoir is controlled by the triple valve. This causes air pressure in the brake pipe to escape.
Some modern systems use disc brakes. The combination minimized braking distances, allowing more full-speed running between stops. Compressed air from the main reservoir is distributed along the train through the main reservoir pipe. The simplest way of doing this is to convert the energy into heat. This is the system by which the movement of the brake cylinder piston transmits pressure to the brake blocks on each wheel.
How Air Brakes Work
Rigging can often be complex, especially under a passenger car with two blocks to each wheel, making a total of sixteen. Rigging requires careful adjustment to ensure all the blocks operated from one cylinder provide an even rate of application to each wheel.
The brake pipe was connected to an air cylinder on each car. This is the friction material which is pressed against the surface of the wheel tread by the upward movement of the brake cylinder piston. The flow of air between the auxiliary reservoir and the brake cylinders is controlled through the triple valve or distributor.
The Railway Technical Website
Changing the level of air pressure in the pipe causes a change in the state of the brake on each vehicle. The next generation of brakes added a compressor to the locomotive.
Use of distributed power i. The connection between the brake cylinder and the exhaust underneath the slide valve has also been closed. This position dumps the brake pipe air quickly.
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