Air Brake System Overview/en: Difference between revisions

Revision as of 00:27, 9 March 2025

Trains are heavy. In order to stop or slow down, they need a lot of braking force. Rather than have one vehicle in a train be equipped with brakes, usually all the vehicles are brake-equipped. When a train is braking, each vehicle in it is braking relatively simultaneously. This is accomplished by a compressed air mechanical brake system that runs throughout the train, simply called the train brake .

Each rail vehicle has an air line hose on either end. When vehicles are coupled together, their air lines are connected too. By controlling air pressure with a single control device in the leading vehicle, the entire train's brakes are controlled. The brake system pressure is created by compressors , which can be found on motorized vehicles . Before going into detail about how the system works, let's get familiar with a few of the primary components:

Main Reservoir

Main reservoir is a high volume vessel found on motorized vehicles that are equipped with a compressor . In most cases it is automatically kept pressurized at around 8 bar . The main reservoir is there to provide pressure to the rest of the system.

Brake Pipe

Brake pipe is a system of air lines spanning through a train. On a properly coupled train, air lines are connected between individual vehicles with their valves open. At the ends of the train, however, the air line valves are closed. This allows the pipe to be pressurized at 5 bar in normal running conditions, by the main reservoir. The volume of a brake pipe is relatively low, but it grows bigger with each additional coupled vehicle.

Auxiliary Reservoirs

Auxiliary reservoirs are medium volume vessels found on each individual vehicle. Pressurized by the brake pipe, they store pressure to be further fed to apply brakes, on demand. While auxiliary reservoirs can take a long time to charge, they are almost impossible to run out during regular operation.

Brake Cylinders

Brake cylinders are low volume vessels found on each individual vehicle, doing the actual braking force application . When pressurized, by auxiliary reservoirs, cylinders press brake shoes against wheels, causing vehicles to slow down.

Train Charging

Due to leaks , no brake system components can remain pressurized indefinitely. It usually takes some time to bring the components of unused vehicles to their nominal, high pressure level, before they can be set in motion. The two biggest factors are the main reservoir, which will charge as quickly as the respective compressor can do it, and auxiliary reservoirs, which may take a long time to charge, depending on how many vehicles there are in the train.

Adding additional locomotives to the train to improve charging speeds is a viable option, as is revving the engine .

Train Brake Application

Train brake is applied by a control device found in motorized rail vehicles. Doing so on a fully charged train functions by air getting dumped from the brake pipe to the atmosphere. This forces auxiliary reservoirs to feed their stored pressure to brake cylinders, pressing brake shoes against wheels.

Train Brake Release

Train brake is released by the same control device. Doing so on a fully charged train functions by the brake pipe getting pressurized by main reservoir. This forces auxiliary reservoirs to recharge from the pipe and no longer feed the brake cylinders, depressing the brake shoes from the wheels.

Automatic Stop Safety Mechanism

Crucial safety feature of the compressed air brake system is that, in case of vehicle connection getting severed, such as due to a derailment , brake pipe pressure will be lost, resulting in automatic full brake application on both remaining train parts. This is integral to the compressed air brake system design.

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 <languages />
-In order for trains to be able to slow down effectively, each containing vehicle needs to apply brakes relatively simultaneously. This is accomplished by the train’s air brake system. Each rail vehicle comes equipped with an air line hose on either end. When vehicles are coupled together, their air lines are connected too, in a handshake manner. This way, the driver in a leading vehicle is able to operate brakes on the entirety of the train, using a single train brake control device.
+{{pll|Rail Vehicle Types|Trains}} are heavy. In order to stop or slow down, they need a lot of braking force. Rather than have one {{pll|Rail Vehicle Types|vehicle}} in a train be equipped with brakes, usually all the vehicles are brake-equipped. When a train is braking, each vehicle in it is braking relatively simultaneously. This is accomplished by a compressed air mechanical brake system that runs throughout the train, simply called the {{pll|Train Brake|train brake}}.
-The air in the brake system is pumped by compressors found onboard the motorized vehicles, and it is shared throughout the train via a system of valves, pipes and hoses. For simplicity, the system can be viewed as composed of three separate units: main reservoir, brake pipe and brake cylinder.
+Each rail vehicle has an air line hose on either end. When vehicles are {{pll|Coupling|coupled}} together, their air lines are connected too. By controlling air pressure with a single [[Train Brake|control device]] in the leading vehicle, the entire train's brakes are controlled. The brake system pressure is created by {{pll|Compressor|compressors}}, which can be found on {{pll|Rail Vehicle Types|motorized vehicles}}. Before going into detail about how the system works, let's get familiar with a few of the primary components:
-Main reservoir is a high volume vessel found onboard motorized vehicles. It is usually kept pressurized to a high level by the onboard compressor, and serves to provide pressure to the rest of the system.
+==== Main Reservoir ====
-Brake pipe, pressurized by the main reservoir, is a system of valves, pipes and hoses stretched throughout a whole train. At every coupling, the airflow can be manually opened or closed, by a valve at its base, called the angle cock. This is done on the ends of the train, to prevent the pressurized air from escaping into the atmosphere. Under normal running conditions the brake pipe holds a pressure of 5 bar.
+Main reservoir is a high volume vessel found on motorized vehicles that are equipped with a {{pll|Compressor|compressor}}. In most cases it is automatically kept pressurized at around {{pll|Monitoring|8 bar}}. The main reservoir is there to provide pressure to the rest of the system.
-Finally, every individual vehicle has one or more of its own brake cylinders. These are low volume vessels that put pressure on a piston, which presses the vehicle’s brake shoes against the wheels, causing it to slow down. A control valve reacts to changes in pressure in the brake pipe, pressurizing the brake cylinders with air accordingly, from specialized vessels found on each vehicle, called auxiliary reservoirs.
+==== Brake Pipe ====
-By operating the train brake lever, the driver controls the brake pipe pressure, indirectly affecting the amount of air supplied to each brake cylinder in the train. By moving the train brake lever in the "apply" direction, the driver dumps air from the brake pipe into the atmosphere. The control valves on each vehicle release pressure contained in the auxiliary reservoirs into the brake cylinders and thus apply the brakes. By moving the train brake lever in the "release" direction, the driver pressurizes the brake pipe with air from the main reservoir. This refills the auxiliary reservoirs and the control valves react by dumping brake cylinder pressure into the atmosphere, releasing the brakes.
+Brake pipe is a system of air lines spanning through a train. On a properly coupled train, air lines are connected between individual vehicles with their valves open. At the ends of the train, however, the air line valves are closed. This allows the pipe to be pressurized at {{pll|Monitoring|5 bar}} in normal running conditions, by the main reservoir. The volume of a brake pipe is relatively low, but it grows bigger with each additional coupled vehicle.
-In case the connection between the vehicles is broken, full brakes will apply automatically on both remaining train parts. This safety feature is integral to the pressurized air brake system design. Brake pipe needs to be fully pressurized so that the brakes are released. When the brake pipe loses all pressure, brakes get fully applied. This is also one of the disadvantages of the system – before a train can be safely set in motion, it must be pressurized first. The longer the train, the longer it takes to pressurize the system, particularly the auxiliary reservoirs. With long trains, adding extra locomotives can help pressurize the system faster.
+==== Auxiliary Reservoirs ====
+Auxiliary reservoirs are medium volume vessels found on each individual vehicle. Pressurized by the brake pipe, they store pressure to be further fed to apply brakes, on demand. While auxiliary reservoirs can take a long time to charge, they are almost impossible to run out during regular operation.
+==== Brake Cylinders ====
+Brake cylinders are low volume vessels found on each individual vehicle, doing the actual {{pll|Monitoring|braking force application}}. When pressurized, by auxiliary reservoirs, cylinders press {{pll|Brake Shoes|brake shoes}} against wheels, causing vehicles to slow down.
+==== Train Charging ====
+Due to {{pll|Cylinder Leaks|leaks}}, no brake system components can remain pressurized indefinitely. It usually takes some time to bring the components of unused vehicles to their nominal, high pressure level, before they can be set in motion. The two biggest factors are the main reservoir, which will charge as quickly as the respective {{pll|Compressor|compressor}} can do it, and auxiliary reservoirs, which may take a long time to charge, depending on how many vehicles there are in the train.
+Adding additional locomotives to the train to improve charging speeds is a viable option, as is {{pll|Compressor|revving the engine}}.
+==== Train Brake Application ====
+{{pll|Train Brake|Train brake}} is applied by a control device found in motorized rail vehicles. Doing so on a fully charged train functions by air getting dumped from the brake pipe to the atmosphere. This forces auxiliary reservoirs to feed their stored pressure to brake cylinders, pressing brake shoes against wheels.
+==== Train Brake Release ====
+{{pll|Train Brake|Train brake}} is released by the same control device. Doing so on a fully charged train functions by the brake pipe getting pressurized by main reservoir. This forces auxiliary reservoirs to recharge from the pipe and no longer feed the brake cylinders, depressing the brake shoes from the wheels.
+==== Automatic Stop Safety Mechanism ====
+Crucial safety feature of the compressed air brake system is that, in case of vehicle connection getting severed, such as due to a {{pll|Derailing|derailment}}, brake pipe pressure will be lost, resulting in automatic full brake application on both remaining train parts. This is integral to the compressed air brake system design.
-{{See also|Coupling|Rail Vehicle Types|Compressor|Lapping|Cylinder Leaks|Monitoring|Train Brake|Independent Brake|Dynamic Brake|Brake Shoes}}
 [[Category:Air Brake System|1]]