What is a railway air brake system?

A railway air brake is a power braking system used on trains that utilizes compressed air as the operating medium to slow down or stop the train. This system is crucial for the safe operation of trains, especially given their significant weight and momentum.

Who is credited with patenting the fail-safe air brake system that is the foundation for modern train brakes?

George Westinghouse patented the fail-safe air brake system on April 13, 1869. This design has been nearly universally adopted in various forms and forms the basis for the braking systems used on most modern trains.

What company was founded to produce and market George Westinghouse's air brake invention?

The Westinghouse Air Brake Company was established to manufacture and sell George Westinghouse's groundbreaking invention, playing a pivotal role in the adoption and development of air brakes in the railway industry.

How does the fundamental Westinghouse air brake system operate regarding air pressure and brake activation?

The system charges air reservoirs on each car with compressed air. Full air pressure releases the brakes, while a reduction or loss of air pressure causes the brakes to apply using the compressed air stored in the car's reservoirs. This pressure-based operation is key to its reliability.

What is the 'straight air system,' and how does it apply brakes?

The straight air system is the simplest form of air brake. It applies brakes by directing compressed air directly to a brake cylinder, which uses its piston to apply force to the brake rigging, pressing brake shoes against the wheels.

How does the brake rigging function in applying brakes?

The brake rigging is a mechanical linkage connected to the brake cylinder's piston. It distributes the force from the cylinder to multiple wheels, pressing brake shoes against the wheel treads to create friction and slow the car. The illustration provided shows a simplified view of this mechanism.

Where is the compressed air for the braking system generated and stored on a locomotive?

Compressed air is generated by an air compressor, typically mounted on the locomotive, and stored in a tank called the main reservoir before being supplied to the brake system. This main reservoir acts as a buffer, ensuring a ready supply of air.

What are the power sources for air compressors on different types of locomotives?

On diesel locomotives, the prime mover drives the compressor. Steam locomotives use a cross-compound steam engine, while electric locomotives typically use their own electric motors to power the compressor.

What is the primary operational drawback of a straight air brake system?

The main weakness of a straight air brake system is its lack of redundancy; any failure in the piping, such as a blown air hose, that causes a loss of pressure will render the brakes inoperative. This makes it unsuitable for controlling an entire train.

Why are straight air brakes suitable for locomotives but not for entire trains?

Straight air is used for locomotive brakes because locomotives have an emergency stopping capability through reversing propulsion ('plugging'). Trains cannot rely on this, so the lack of redundancy in straight air systems makes them unsuitable for the whole train, where a failure could be catastrophic.

What is the purpose of the 'independent brake valve' on a locomotive?

The independent brake valve controls the locomotive's brakes, allowing them to be applied or released separately from the train brakes. This provides the engineer with finer control over the locomotive's braking independently of the rest of the train.

What crucial components did George Westinghouse introduce to each railway car to create a more reliable braking system?

To overcome the limitations of the straight air system, Westinghouse equipped each car with a dual-compartment, compressed-air reservoir and a 'triple valve,' also known as a control valve. These components allowed for a more sophisticated and fail-safe operation.

How is the 'brake pipe' utilized in the Westinghouse air brake system?

The brake pipe runs along the length of the train, connecting cars via hoses. It serves as the conduit for compressed air that, when reduced in pressure, signals the triple valve to apply the brakes. Hoses at each end of the cars ensure a continuous connection throughout the train.

How does the Westinghouse air brake system apply brakes, contrasting with the straight air system?

The Westinghouse system applies brakes indirectly by *reducing* the air pressure in the brake pipe, whereas the straight air system applies brakes by *increasing* air pressure in the brake cylinder. This inverse logic is key to its fail-safe nature.

What were the three original valvular functions within Westinghouse's triple valve device?

The original triple valve contained a diaphragm-operated poppet valve for feeding reservoir air to the brake cylinder, a reservoir charging valve, and a brake cylinder release valve. These components worked together to manage air flow for braking.

How did the design of the triple valve evolve over time?

George Westinghouse later improved the triple valve by replacing the poppet valve action with a piston valve, a slide valve, and a graduating valve. This refinement enhanced the valve's performance and reliability.

What is a 'service reduction' in the context of operating the Westinghouse air brake?

A service reduction is a controlled, gradual decrease in brake pipe air pressure, typically initiated by the train operator to slow down or stop the train smoothly. This controlled reduction allows for precise braking adjustments.

Describe the process of applying brakes during a 'service reduction.'

During a service reduction, the triple valve closes the brake cylinder exhaust, opens a port to charge the brake cylinder from the car's reservoir, and applies the brakes. It then seals ('laps off') when pressures equalize to maintain the application, preventing further air flow until the brake pipe pressure changes again.

How are the brakes released and the reservoirs recharged in the Westinghouse system?

Releasing the brakes occurs when brake pipe pressure is increased above reservoir pressure. The triple valve then vents the brake cylinder to the atmosphere, releasing the brakes, and simultaneously opens a port to recharge the reservoirs from the brake pipe, preparing them for the next application.

What defines an 'emergency application' of the brakes in the Westinghouse system?

An emergency application is triggered by a rapid, uncontrolled reduction in brake pipe pressure, signaling the need for maximum braking force. This rapid pressure drop is distinct from the controlled reduction of a service application.

How does an emergency application differ from a service application in terms of brake force and speed of application?

Emergency applications utilize the full pressure from both reservoir sections to the brake cylinder for maximum force and include a local venting of the brake pipe to atmosphere to ensure rapid propagation of the pressure loss throughout the train. This results in a much faster and more forceful brake application.

Why is the local venting feature crucial during an emergency application on long trains?

Local venting accelerates the pressure drop along the brake pipe, ensuring that triple valves on cars further down the train also trigger an emergency response. Without it, the pressure loss might be too slow, potentially causing dangerous slack action (sudden bunching or stretching) between cars, which could lead to a derailment.

What inherent safety feature makes the Westinghouse air brake system 'fail-safe'?

The system is fail-safe because any unintended loss of brake pipe pressure, such as from a broken hose or a disconnected coupling, automatically triggers an immediate application of the brakes. This ensures that a loss of air pressure does not lead to uncontrolled movement.

What are the two main functions performed by modern air brake systems?

Modern systems perform 'service' braking for routine operations, allowing for controlled speed adjustments, and 'emergency' braking for rapid application in critical situations or when system integrity is compromised.

How does the timing of brake application differ between service and emergency applications on long trains?

Service applications take several seconds to propagate through a long train due to flow resistance in the brake pipe, potentially causing slack run-in. Emergency applications are much faster due to the rapid pressure venting, minimizing slack action and providing quicker stopping power.

What are the two distinct air brake systems found on modern locomotives, and what is their relationship?

Modern locomotives have the 'automatic brake,' which controls the entire train's service and emergency braking, and the 'independent brake.' The independent brake is a straight air system that applies brakes solely to the lead locomotive consist, allowing for more precise control and maneuverability.

What is the 'bail off' function of the independent brake system?

The 'bail off' mechanism, part of the independent brake system, allows the operator to release the brakes on the lead locomotives independently, without affecting the brakes on the rest of the train. This is essential for handling the locomotive during certain operations.

How does an emergency brake application increase braking force compared to a service application?

Emergency applications direct air from both the service and emergency sections of the dual-compartment reservoir to the brake cylinder, resulting in a 20-30% stronger application than service applications. This provides maximum stopping power when needed.

What role does the auxiliary vent port play in ensuring emergency brake effectiveness on long trains?

This port, part of the triple valve's emergency portion, locally vents the brake pipe to atmosphere during an emergency. This action accelerates the pressure reduction rate along the entire train, ensuring the emergency function is triggered consistently, even on very long consists.

How can 'distributed power' (mid-train or rear-end locomotives) improve brake application on long trains?

Distributed power units receive radio signals to initiate brake pressure reductions locally. This action propagates quickly through nearby cars, reducing the time lag associated with brake applications on very long trains and improving overall control.

What are 'distributors,' and how do they enhance upon older triple valve technology?

Distributors are components in modern air brake systems that replace triple valves. They offer additional functionality, such as the ability to partially release the brakes, which older triple valves could not perform. This allows for more nuanced control.

What are the typical working pressures for the main reservoir and brake pipe in American freight and passenger trains?

The main reservoir is usually charged to 125-140 psi (pounds per square inch). Freight trains typically operate with a 90 psi brake pipe, while passenger trains use a higher 110 psi brake pipe pressure.

Under what specific condition might a leak in the brake pipe *not* trigger an emergency brake application?

A slow leak that gradually reduces brake pipe pressure to zero, such as when the air compressor is not functioning and thus not maintaining pressure, will not cause an emergency application. Only a rapid pressure reduction triggers the emergency function.

What is an 'electro-pneumatic' (EP) brake system, and what is its main advantage?

EP brakes are a type of air brake that allows for the immediate, simultaneous application of brakes throughout the entire train. This contrasts with conventional air brakes, where application is sequential and takes time to propagate.

In what regions and during what periods have electro-pneumatic brakes seen significant use?

EP brakes have been used in British practice since 1949, in German high-speed trains like the ICE since the late 1980s, and were undergoing testing in North America and South Africa around 2005. Passenger trains have often utilized a three-wire version for multiple braking levels.

Describe the function of the electro-pneumatic master controller in North American high-speed brake systems.

This controller compares the pressure in a secondary straight-air trainline with the pressure set by the engineer's valve. It then signals magnet valves on each car to open simultaneously, rapidly changing the pressure in the straight-air trainline for controlled braking, offering greater responsiveness than conventional systems.

What safety features were incorporated into North American high-speed passenger train braking systems using electro-pneumatic controls?

These systems included axle-mounted speed sensors and anti-lock brake equipment. The speed sensors adjusted braking force based on speed (full force above 60 mph, reduced at lower speeds), while anti-lock systems prevented wheel lock-up, collectively minimizing braking distances.

How do some later air brake systems utilize a 'train wire' for safety?

In these systems, a 'train wire' must be kept energized to keep the brakes released. If the train divides, breaking the wire, it ensures all motors are switched off and both sections of the train immediately apply emergency brakes, providing a fail-safe mechanism for train separation.

What is the key innovation of Electronically Controlled Pneumatic Brakes (ECP)?

ECP brakes use a local area network (LAN) to connect brakes on all wagons and locomotives. This allows for individual control of each wagon's brakes and the reporting of their performance back to the control system, offering advanced diagnostics and control.

What is a significant limitation of conventional air brake systems concerning long trains and brake release?

Fully recharging the air reservoirs on a long train can take a considerable amount of time (8-10 minutes). During this period, the brake pipe pressure is lower than optimal, which can affect braking effectiveness if further applications are needed before full recharge.

What is the danger of making multiple, rapid brake pipe reductions, a practice known as 'fanning the brake'?

Repeated, rapid brake pipe reductions can severely deplete car reservoir pressure, leading to substantially reduced braking force. On a descending grade, this depletion can result in a runaway train, as the brakes may fail to hold the train's weight.

How can an engine driver attempt to regain control if braking is lost due to reservoir depletion?

An emergency brake application can often restore control, as the emergency portion of the reservoir is typically fully charged and not affected by service reductions. However, if the brake pipe pressure is too low, even an emergency application may not be sufficient to trip the triple valves.

What is 'blended braking,' and when is it typically employed?

Blended braking involves the simultaneous application of dynamic (locomotive) brakes and train brakes. It is often used on descending grades to maintain a safe speed and keep train slack bunched, which helps prevent draw-gear damage that could occur from sudden slack run-out upon brake release.

What is the function of the 'main reservoir pipe' in a two-pipe air brake system?

The main reservoir pipe is continuously supplied with air directly from the locomotive's main reservoir. This allows car reservoirs to be charged independently of the brake pipe, improving recharge times and reducing pressure loss issues, especially on long trains.

What are 'angle cocks,' and what is their role in maintaining brake pipe continuity?

Angle cocks are valves located at the ends of cars and locomotives that connect the brake pipe to air hoses. They must be opened on intermediate cars to create a continuous brake pipe for the system to function correctly, allowing air pressure to travel the length of the train.

What is the correct configuration of angle cocks on the lead and rear cars of a train for normal operation?

For normal operation, the angle cock on the rear end of the last car and the forward end of the lead locomotive or car are closed to seal the brake pipe and maintain its integrity. This prevents air from escaping at the train's extremities.

What is the consequence of an unintentionally closed angle cock on an intermediate car?

If an intermediate angle cock is closed, it isolates a section of the brake pipe. This can lead to a loss of braking capability in that segment or, if the segment maintains pressure, a loss of braking for those cars, potentially making them uncontrollable.

How did a closed angle cock contribute to the 1953 Pennsylvania Railroad train wreck involving the *Federal Express*?

A closed angle cock near the front of the train isolated a significant portion of the brake pipe, rendering most of the train's brakes inoperative. This prevented the engineer from controlling its speed on a descending grade, leading to the catastrophic accident.

What are the typical safeguards implemented to prevent brake failures related to angle cock operation?

Railroads implement strict procedures for conducting air brake tests during train makeup and en route operations. These tests include verifying the correct positioning of angle cocks to ensure proper brake pipe continuity and function.

Describe the purpose of the visual and telemetry checks performed during a typical air brake test.

These checks verify that brakes are applying and releasing correctly and that brake pipe continuity extends to the rear of the train. Often, an automated end-of-train device (ETD) is used for telemetry to confirm rear-end continuity and brake status.

What does a brake failure on one or more cars typically indicate if brake pipe continuity is confirmed?

If brake pipe continuity is confirmed, a brake failure on specific cars usually indicates malfunctioning triple valves or, less commonly, issues with the brake rigging itself. These components are responsible for applying the brakes on individual cars.

Railway Air Brake Wiki: The Mechanics of Motion: A Deep Dive into Railway Air Brakes

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Overview

Core Functionality

A railway air brake is a power braking system utilizing compressed air as its operational medium. The modern iteration, based on George Westinghouse's 1869 patent, is a fail-safe system, meaning any loss of pressure automatically applies the brakes.

This system relies on maintaining air pressure within a dedicated 'brake pipe' running the length of the train. Full pressure releases the brakes, while any reduction in pressure triggers their application using stored air on each car.

Westinghouse Air Brake Company

The invention led to the establishment of the Westinghouse Air Brake Company, which became instrumental in the widespread adoption of this critical safety technology across global railways.

Its near-universal adoption underscores its effectiveness and reliability in managing the immense forces involved in train operation.

Global Standard

While variations exist, the fundamental principles pioneered by Westinghouse remain the bedrock of most modern train braking systems worldwide. This technology is crucial for the safe and efficient movement of both passengers and freight.

Straight Air Brake

Basic Mechanism

In its simplest form, a straight air system directs compressed air directly to a brake cylinder. This cylinder's piston applies force via mechanical linkage (the brake rigging) to press brake shoes against the wheels, dissipating kinetic energy as heat.

The compressed air originates from an air compressor on the locomotive, stored in a main reservoir.

Critical Vulnerability

The primary drawback of a straight air system is its lack of redundancy. Any failure in the air piping, such as a ruptured air hose, results in a complete loss of braking capability.

Consequently, this system is generally unsuitable for controlling entire trains but is often used for locomotive brakes, where alternative stopping methods (like reversing propulsion) exist.

Westinghouse Innovation

The Triple Valve

Westinghouse's breakthrough involved equipping each car with a dual-compartment reservoir and a triple valve (or control valve). A continuous brake pipe connected these components throughout the train via hoses.

This system cleverly uses a reduction in brake pipe pressure to indirectly apply the brakes, fundamentally differing from the direct application of straight air systems.

Service vs. Emergency

Service Application: A controlled, gradual reduction in brake pipe pressure triggers the triple valve to apply brakes proportionally, allowing for smooth speed adjustments.

Emergency Application: A rapid, uncontrolled pressure drop (due to a leak, break-in-two, or deliberate action) activates the triple valve's emergency function, applying maximum braking force. This rapid venting is crucial for ensuring brake application across long trains.

Fail-Safe Design

The inherent design ensures safety: any disruption to the brake pipe's air pressure automatically triggers the brakes. This redundancy is paramount for preventing runaway trains.

Modern Systems

Dual Functionality

Modern air brake systems manage two primary functions:

Service Braking: Controlled applications and releases for normal operation.
Emergency Braking: Rapid, forceful application triggered by system failures or immediate danger.

Controlled Application

During service applications, the engineer initiates a gradual pressure reduction. The inherent resistance in the brake pipe causes a slight delay in application along the train, allowing for smoother transitions and mitigating excessive 'slack action' (sudden bunching or stretching of train cars).^[8]

Independent vs. Automatic

Locomotives typically feature two systems: the automatic brake controlling the entire train, and the independent brake (a straight air system) managing only the locomotive consist. This allows for nuanced control, including releasing locomotive brakes without affecting the train brakes ('bail off').

Enhancements

Electro-Pneumatic (EP) Brakes

EP brakes utilize an electrical signal alongside pneumatic pressure for near-instantaneous brake application across the entire train, significantly reducing application times compared to purely pneumatic systems.^[9] This technology has been employed in high-speed trains, notably in Europe.

Electronically Controlled Pneumatic (ECP) Brakes

ECP systems represent a further evolution, employing a data network (like a Local Area Network) to connect and individually control brakes on each car. This allows for precise management, real-time diagnostics, and reporting of brake performance for every component.^[9]

Two-Pipe System

Many modern systems incorporate a second pipe, the main reservoir pipe, which is continuously pressurized directly from the locomotive's main reservoir. This allows car reservoirs to recharge independently of the brake pipe, significantly speeding up brake release times and improving reliability, especially on long trains.^[10]

Limitations

Recharging Time

A key limitation is the time required to recharge reservoirs on long trains. This process can take 8-10 minutes or more, during which the brake pipe pressure remains lower than optimal.^[10]

Repeated service applications before full recharge can deplete reservoir pressure, potentially leading to significantly reduced braking force and, on gradients, a dangerous runaway condition.

Pressure Loss Sensitivity

While designed to be fail-safe, the system's effectiveness relies on maintaining brake pipe integrity. Slow leaks might not trigger an emergency application, and severe pressure depletion can render even emergency applications ineffective if the volume of air isn't sufficient to activate the triple valves.^[8]

Mechanical Complexity

The numerous valves, pipes, and reservoirs, while robust, are susceptible to mechanical failure or human error (e.g., incorrectly closed angle cocks). These issues can inadvertently disable braking capabilities on portions of the train.^[11]

European Systems

Standardization

European brake systems, while diverse historically, now largely adhere to standards like EN 14198, based on UIC Leaflet 540. This ensures interoperability across different national networks.^[12]

Approved systems include those from Knorr-Bremse, Oerlikon, SAB-WABCO, and Dako, among others.

Historical Context

Historically, Britain utilized both vacuum and air brakes, gradually standardizing on vacuum brakes before transitioning back to air brakes in the diesel era. Some locomotives were 'dual-fitted' to operate with both systems.^[14]

Accidents & Failures

Consequences of Failure

Brake failure on heavy, high-inertia trains, especially those carrying hazardous materials, can lead to catastrophic accidents, resulting in significant loss of life, property damage, and environmental harm.

Conversely, even functional brakes can cause issues, particularly with 'empty' freight cars ('empties') where wheels may lock, overheat, and potentially fracture, leading to derailments.

Angle Cock Errors

Improperly positioned angle cocks (valves connecting brake pipes) are a common source of failure. Closing the wrong valve can isolate sections of the brake pipe, leading to partial or complete loss of braking capability. Historical accidents, like the 1953 Pennsylvania Railroad train wreck, have been attributed to such errors.^[11]

Safeguards and Testing

Rigorous procedures, including comprehensive air brake tests during train makeup and en route, are mandated to prevent failures. These tests verify brake application, release, and continuity throughout the train, often utilizing automated end-of-train devices (ETDs) for monitoring.^[11]

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References

Railway regulations consider "Westinghouse" as a standalone brake system, however to distinguish from Westinghouse company and other Westinghouse brake systems, railway staff often borrow letter "W" from signs on UIC rolling stock

Railway regulations consider "knorr" as a standalone brake system, however to distinguish from Knorr company and other Knorr brake systems, railway staff often borrow letter "K" from signs on UIC rolling stock

U.S. patent 88,929

The new Westinghouse brakes were explained to the railroad workers in many books. See, for example, A Textbook on the Westinghouse Air Brake (Scranton: International Textbook School, 1900).

A full list of references for this article are available at the Railway air brake Wikipedia page

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Important Notice

This page was generated by an Artificial Intelligence and is intended for informational and educational purposes only. The content is based on a snapshot of publicly available data from Wikipedia and may not be entirely accurate, complete, or up-to-date.

This is not technical advice. The information provided on this website is not a substitute for professional engineering consultation, diagnosis, or treatment related to railway systems. Always refer to official technical documentation and consult with qualified professionals for specific applications or safety concerns. Never disregard professional advice because of something you have read on this website.

The creators of this page are not responsible for any errors or omissions, or for any actions taken based on the information provided herein.

The Mechanics of Motion

💡 Dive in with Flashcard Learning! 💡

🚂 Overview 💨

⚙️ Core Functionality

🏢 Westinghouse Air Brake Company

🌍 Global Standard

➡️ Straight Air Brake ⚠️

🔧 Basic Mechanism

❌ Critical Vulnerability

💡 Westinghouse Innovation ✅

🧩 The Triple Valve

🔄 Service vs. Emergency

🔒 Fail-Safe Design

🚀 Modern Systems 💡

duality Dual Functionality

🚦 Controlled Application

⚖️ Independent vs. Automatic

✨ Enhancements ⚡

⚡ Electro-Pneumatic (EP) Brakes

🧠 Electronically Controlled Pneumatic (ECP) Brakes

➕ Two-Pipe System

⚠️ Limitations ⏳

⏳ Recharging Time

💨 Pressure Loss Sensitivity

⚙️ Mechanical Complexity

🇪🇺 European Systems 🌍

📜 Standardization

🔄 Historical Context

💥 Accidents & Failures 🔥

❗ Consequences of Failure

📐 Angle Cock Errors

✅ Safeguards and Testing

🔗 Related Topics 📚

🔗 Key Concepts

🏭 Manufacturers

Teacher's Corner 🧑‍🏫

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Gamer's Corner 🎮

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References

📜 References

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⚠️ Disclaimer 📜

❗ Important Notice

Dive in with Flashcard Learning!

Overview

Core Functionality

Westinghouse Air Brake Company

Global Standard

Straight Air Brake

Basic Mechanism

Critical Vulnerability

Westinghouse Innovation

The Triple Valve

Service vs. Emergency

Fail-Safe Design

Modern Systems

Dual Functionality

Controlled Application

Independent vs. Automatic

Enhancements

Electro-Pneumatic (EP) Brakes

Electronically Controlled Pneumatic (ECP) Brakes

Two-Pipe System

Limitations

Recharging Time

Pressure Loss Sensitivity

Mechanical Complexity

European Systems

Standardization

Historical Context

Accidents & Failures

Consequences of Failure

Angle Cock Errors

Safeguards and Testing

Related Topics

Key Concepts

Manufacturers

Teacher's Corner

True or False?

Test Your Knowledge!

Gamer's Corner

Discover other topics to study!

References

Feedback & Support

Disclaimer

Important Notice