Air Brake System Overview/en: Difference between revisions

Latest revision as of 23:30, 17 April 2025

Every rail vehicle is equipped with mechanical brakes . They function by physically pressing brake shoes against the wheels. The shoes can be pressed manually with handbrakes , or automatically with compressed air.

Applying brakes with compressed air is quicker, which is why some vehicles are equipped with independent brakes , rather than just handbrakes. More importantly, compressed air allows brakes to be applied synchronously throughout an entire train, with the so called train brake . The primary components that make the compressed air brake system are:

Main Reservoir

Main reservoir is a high volume vessel found on motorized vehicles . This reservoir contains air, which is usually automatically pumped up to 8 bar by an onboard compressor . The main reservoir is there to provide pressure for the brake system, but sometimes also other systems, such as horns and wipers .

Brake Pipe

Brake pipe is a system of air lines designed to distribute compressed air throughout an entire train. On a properly coupled train, air line hoses are connected between individual vehicles with their valves open. At the ends of the train, however, the valves are closed. This allows the pipe to be pressurized at 5 bar in normal running conditions, throughout the train, by available main reservoirs. The volume of brake pipes 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 compressed air that is ready to apply brakes on demand. While auxiliary reservoirs can take a long time to charge, depending on the amount of vehicles in a train, they practically never 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.

Brake cylinder pressure can be manually dumped in situations where that may be desired.

Brake Control Valve

Compressed air brakes, be it independent or train , are operated by control valves found in motorized vehicles' cabs , usually in the form of levers. There are different types of control valves and they need to be properly cut in in order to function.

Train Charging

Due to leaks , no brake 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 reservoirs, which will charge as quickly as the respective compressor(s) allow 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, and so is revving the engine .

Automatic Stop Safety Mechanism

Crucial safety feature of the compressed air brake system is that, in case a vehicle connection is severed, such as due to a derailment , emergency brakes are automatically applied on both remaining train parts. This is because the brake pipe pressure is lost to the atmosphere, and it is integral to the compressed air brake system design in trains.

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-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.
-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.
+Every {{pll|Rail Vehicle Types|rail vehicle}} is equipped with mechanical {{pll|Braking Overview|brakes}}. They function by physically pressing {{pll|Brake Shoes|brake shoes}} against the wheels. The shoes can be pressed manually with {{pll|Handbrake|handbrakes}}, or automatically with compressed air.
-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.
+Applying brakes with compressed air is quicker, which is why some vehicles are equipped with {{pll|Independent Brake|independent brakes}}, rather than just handbrakes. More importantly, compressed air allows brakes to be applied synchronously throughout an entire train, with the so called {{pll|Train Brake|train brake}}. The primary components that make the compressed air brake system are:
-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 ====
-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.
+Main reservoir is a high volume vessel found on {{pll|Rail Vehicle Types|motorized vehicles}}. This reservoir contains air, which is usually automatically pumped up to {{pll|Monitoring|8 bar}} by an onboard {{pll|Compressor|compressor}}. The main reservoir is there to provide pressure for the brake system, but sometimes also other systems, such as {{pll|Horns, Bells & Whistles|horns}} and {{pll|Wipers|wipers}}.
-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 ====
-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.
+Brake pipe is a system of air lines designed to distribute compressed air throughout an entire train. On a properly coupled train, air line hoses are connected between individual vehicles with their valves open. At the ends of the train, however, the valves are closed. This allows the pipe to be pressurized at {{pll|Monitoring|5 bar}} in normal running conditions, throughout the train, by available main reservoirs. The volume of brake pipes 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 compressed air that is ready to apply brakes on demand. While auxiliary reservoirs can take a long time to charge, depending on the amount of vehicles in a train, they practically never 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 {{pll|Brake Shoes|brake shoes}} against wheels, causing vehicles to slow down.
+Brake cylinder pressure can be {{pll|Manual Cylinder Release|manually dumped}} in situations where that may be desired.
+==== Brake Control Valve ====
+Compressed air brakes, be it {{pll|Independent Brake|independent}} or {{pll|Train Brake|train}}, are operated by control valves found in {{pll|Rail Vehicle Types|motorized vehicles' cabs}}, usually in the form of levers. There are {{pll|Lapping|different types of control valves}} and they need to be properly {{pll|Brake Cutout|cut in}} in order to function.
+==== Train Charging ====
+Due to {{pll|Cylinder Leaks|leaks}}, no brake 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 reservoirs, which will charge as quickly as the respective {{pll|Compressor|compressor(s)}} allow 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, and so is {{pll|Compressor|revving the engine}}.
+==== Automatic Stop Safety Mechanism ====
+Crucial safety feature of the compressed air brake system is that, in case a vehicle connection is severed, such as due to a {{pll|Derailing|derailment}}, emergency brakes are automatically applied on both remaining train parts. This is because the brake pipe pressure is lost to the atmosphere, and it is integral to the compressed air brake system design in trains.
-{{See also|Coupling|Rail Vehicle Types|Compressor|Lapping|Cylinder Leaks|Monitoring|Train Brake|Independent Brake|Dynamic Brake|Brake Shoes}}
 [[Category:Air Brake System|1]]