Railroads are the backbone of the United States, moving goods and people across the country, freeing up road congestion and hauling things too heavy or toxic for semi-trucks to handle. Millions of tons of freight are on the railways at any given time, managed by complex systems of personnel and technology consistently improved since the first steam locomotives were invented in the early 1800s. The braking systems of these massive diesel-powered trains rely on air pressure to stop loads weighing hundreds of thousands of pounds, but how do they really work?
Where Does the Air Come From?
Air brakes rely on compressed air stored in tanks on each car. During transit, the pressure is maintained through air lines leading from the engines. When the cars are sitting uncoupled from train engines for periods of time, they are usually connected to a yard air system to maintain pressure and find tanks, valves and lines which need to be replaced or repaired. The brakes are frequently tested to ensure that they work to stop the car when needed. This air system is filtered to avoid contaminants from causing damage and buildup in the brake system.
How Are They Engaged?
Technically speaking, railcar air brakes are always engaged and need to be disengaged for travel by sending air pressure from the locomotive to the brake line. Once the brake line is pressurized, a valve is switched and the brakes are released, if the pressure is released, the valve is switched back and the brakes engage. Since the brakes are on each car as well as the locomotive, if one fails, the rest of the train can compensate, and runaways are less likely. This failsafe is one of the many improvements during the last century to improve the safety of railroads.
How Are Leaks Handled?
Leaks are inevitable and some leakage is expected in every pressurized air system. When trains are stopped at yards for storage or unloading, any issues which came up during transport are addressed. Braking systems are regularly inspected on all locomotives and cars with qualified railroad workers making repairs or replacements as needed. Many rail yards even have machining shops on-site to repair and create the needed components as well as fix the cars and locomotives from wear and tear as well as accidental damage.
Millions of tons of cargo and passengers travel across the US on the railroads every day, bringing the goods and tourists your town needs to thrive. These systems have been in almost continuous use for nearly two centuries with upgrades to safety, efficiency and equipment ongoing. Knowing how the air brake systems work can help you have more confidence in this vital transportation system.