A brake air brake is an electric train brake system brake with compressed air as the operating medium. The modern train relies on an unsafe airbrake system based on George Westinghouse's patented design on March 5, 1868. The Westinghouse Air Brake Company was later organized to produce and sell the invention of Westinghouse. In various forms, it has been almost universally adopted.
The Westinghouse system uses air pressure to fill the reservoir water (tank) in each car. Full air pressure signals every car to release the brakes. Decrease or loss of air pressure signals every car to apply its brakes, using compressed air in its reservoir.
Video Railway air brake
Overview
Air brake straight
In the simplest form of air brakes, called straight air systems , compressed air drives on the pistons in a cylinder. The piston is connected through a mechanical connection to the brake shoe that can rub on the train wheel, using the friction generated to slow the train. Mechanical linkage can be very complicated, as it evenly distributes the force from a pressurized air cylinder to 8 or 12 wheels.
Pressurized air comes from air compressors in locomotives and is shipped from car to car by the railway line consisting of pipes under every car and hose between cars. The main problem with a straight air braking system is that any separation between hose and pipe causes the loss of air pressure and hence the loss of force applying the brakes. This could easily lead to an escaped train. A straight air brake is still used on locomotives, although as a dual circuit system, usually with each bogie (truck) has its own circuit.
Westinghouse air brake
To design a system with no shortage of straight air systems, Westinghouse created a system in which each section of the train carriage was fitted with an air reservoir and a triple valve, also known as a control valve .
Unlike straight air systems, the Westinghouse system uses reduction in the air pressure on the train tracks to apply the brakes.
This three valve is described as so named for performing three functions: Filling air into a ready-to-use air tank, applying the brakes, and releasing it. Thus, it supports certain other actions (ie 'holding' or maintaining the application and allowing the removal of brake cylinder pressure and recharging from the reservoir during release). In its patent application, Westinghouse refers to a 'valve device three' because of the three valve parts components comprising it: a diaphragm-operated poppet valve that drains reservoir air into the brake cylinder, reservoir filling valve, and cylinder brake removal valve. When he immediately fixes the device by removing the action of the popup valve, these three components become the piston valve, the sliding valve, and the passing valve.
- If the pressure on the train line is lower than the reservoir, the brake cylinder disposal portal is closed and air from the car reservoir is inserted into the brake cylinder. The pressure increases in the cylinder, applying the brakes, while decreasing in the reservoir. This action continues until the equilibrium between the pressure of the brake pipe and reservoir pressure is reached. At that point, the air flow from the reservoir to the brake cylinder is stopped and the cylinder is maintained at a constant pressure.
- If the pressure on the train line is higher than the reservoir, the triple valve connects the train line to the reservoir feed, causing the air pressure in the reservoir to increase. The triple valve also causes the brake cylinder to become exhausted into the atmosphere, releasing the brakes.
- Due to the pressure on the train track and the reservoir balance equalizing, the triple valve closes, causing air in the reservoir to be sealed, and the brake cylinder unstressed.
When the engine operator applies the brakes by operating the locomotive brake valve, the railway runs into the atmosphere at a controlled rate, reduces the carriage pressure and in turn triggers a triple valve on each car to supply air into its brake cylinder. When the engine operator releases the brake, the locomotive brake valve portal into the atmosphere is closed, allowing the railway line to be recharged by the locomotive compressor. The subsequent increase in railway pressure causes the valve to triple on each car to dispose of the cylinder's contents into the atmosphere, releasing the brakes and refilling the reservoir.
The Westinghouse system thus fails safely - any failure in the railway line, including the break-in-two of the car, will result in the loss of railway pressure, causing the brake to be applied and the carriage stopped, preventing the car from approaching.
Modern system
Modern air brake systems serve two functions:
- The brake service system, which is in effect and releases the brakes during normal operation, and
- Emergency brake system, which applies the brakes quickly in case of brake pipe failure or emergency application by the machine operator (usually referred to as automatic brake).
When a train brake is applied during normal operation, the machine operator makes a "service application" or "service tariff reduction", which means that the pressure of the train line is reduced at the controlled level. It takes a few seconds for the pressure of the railway to reduce and consequently takes a few seconds for the brakes to be applied across the train. If a train needs to stop an emergency, the machine operator can make an "emergency app", which quickly and instantly transfers all the pressure of the train line into the atmosphere, resulting in fast train brake applications. Emergency applications also occur when the train line is separated or fails, because all air will also soon be released into the atmosphere.
In addition, emergency applications carry additional components of any car air brake system: emergency parts. The triple valve is divided into two parts: the service part, which contains the mechanisms used during brake applications made during service reductions, and the emergency section, which feels the immediate release of train line pressure. In addition, each car air brake reservoir is divided into two parts - service portion and emergency section - and is known as "dual-compartment reservoir". Normal service applications transfer air pressure from the service part to the brake cylinder, while emergency applications cause the triple valve to direct all air both in servicing portions and the emergency section from the double compartment reservoir to the brake cylinder, resulting in 20 -30% stronger Applications.
The emergency section of each triple valve is activated by a very fast train line pressure reduction rate. Due to the length of the train and the diameter of the small rail line, the high reduction rate near the front of the train (in case of emergency applications operated by the machine operator) or near the lane line break (in case the train line comes apart). Further from an emergency application source, the rate of reduction can be reduced to the point where three valves will not detect the application as an emergency reduction. To prevent this, each emergency section of the triple valve contains an additional ventilation port, which, when activated by emergency applications, also locally directs the pressure of the direct train line into the atmosphere. This works to spread emergency applications quickly throughout the entire train.
The use of distributed power (eg, locally-controlled locomotives in mid-rail and/or at the rear) somewhat eases the time-lag problem with long trains, since telemetered radio signals from machine operators in the front locomotives instruct distant units to started a brake pressure reduction that spread rapidly through nearby cars.
Working pressure
The locomotive compressor fills the main reservoir with air at 125-140 psi (8.6-9.7 bar; 860-970 kPa). The train brake is released by plugging air into the train pipe through the engineer's brake valve. The fully charged brake pipes are usually 70-90 psi (4.8-6.2 bar, 480-620 kPa) for freight trains and 110 psi (7.6 bar, 760 kPa) for passenger trains. The brake is applied when the technician moves the brake handle to the "service" position, which causes pressure reduction on the train pipe. In normal braking, the pressure on the railway pipe is not reduced to zero. If it falls to zero, (for example, due to a broken brake hose) an emergency brake application will be created.
Maps Railway air brake
Enhancements
Electro-pneumatic brake or EP is a type of air brake that allows immediate brake applications across trains instead of sequential applications. The EP brakes have been applied in the UK since 1949 and are also used in high-speed German trains (especially ICE) since the late 1980s, they are fully described in electro-pneumatic brake systems on British railway trains. Electro-pneumatic brakes are currently being tested in North America and South Africa in coal ore mining and rail services.
Passenger trains have long had a 3-wire version of an electro-pneumatic brake, which gives seven levels of braking force. In many cases unsafe-fail systems, with sequentially energized wires to apply the brakes, but conventional automated air brakes are also provided to act as a safe failure, and in many cases can be used independently in the event. EP brake failure.
In North America, Westinghouse Air Brake provides High Speed ​​Control brake equipment for some of the simplified post World War II passenger trains. This is an electronically controlled overlay on a conventional D-22 passenger and 24-RL locomotive equipment. On the conventional side, the control valve regulates the reference pressure in volume, which regulates the pressure of the brake cylinder through the relay valve. On the electric side, pressure from the second straight rail controls the relay valve through a two-way valve. These "straight air" trains are charged (from a reservoir in every car) and released by magnetic valves on every car, electrically controlled by wire 3, in turn controlled by "electro-pneumatic master controllers" in locomotive controllers. This controller compares the pressure in the straight-line carriage with that supplied by the self lapping portion of the engine valve, indicating all the magnetic valves "apply" or "release" on the train to be opened simultaneously, changing the pressure in the "straight air" of the train much faster and evenly distributed from possible by simply supplying air directly from the locomotive. Relay valves are equipped with four diaphragms, magnetic valves, electrical control equipment, and speed sensors mounted on the shaft, so at speeds greater than 60 mph (97 m/h) the full braking force is applied, and decreases in steps at 60 mph (97 km/h) 40 and 20 mph (64 and 32 km/h), bringing the train to a stop gently. Each axle is also equipped with anti-lock brake equipment. Combinations minimize the braking distance, allowing more full-speed runs between stops. "Air straight" (electro-pneumatic training paths) , anti-lock, and speed pass parts of the system are independent of each other in any way, and any or all of these options can be assigned separately.
Then the system replaces the automatic air brake with the power cord (in England, at least, known as the "wire rod wound") that must remain energized to keep the brakes.
The latest innovation is an electronically controlled pneumatic brake in which all car brakes (cars) and locomotives are connected by some kind of local area network , allowing individual controls on the brakes on each cart, and reporting the performance of each wagon cart.
Limitations
The Westinghouse air brake system is very reliable, but not perfect. Remember that the car reservoir recharge only when the brake pipe pressure is higher than the reservoir pressure, and that the car's reservoir pressure will rise only to the equilibrium point. Fully loaded reservoirs on long trains may take quite a long time (8 to 10 minutes in some cases), where brake pipe pressure will be lower than locomotive locomotive pressure.
If the brakes should be applied before the filling has been completed, a larger reduction of brake pipe will be required to achieve the desired amount of braking effort, since the system starts at a lower point of equilibrium (lower overall pressure). If a lot of brake pipe reductions are made in a short succession ("fanned brakes" in slag trains), a point can be reached where the reservoir pressure of the car will be very exhausted, thus substantially reducing the piston force of the brake cylinder, causing the brakes to fail. In the descending class, unfavorable results will be an escape.
In case of braking losses due to reservoir depletion, the engine driver may be able to regain control with emergency brake applications, since the emergency portion of each dual-compartment car reservoir must be fully charged - it is not affected by normal service reductions. The three valves detect an emergency reduction based on the brake tube pressure reduction. Therefore, as long as sufficient air volume can be quickly removed from the brake pipe, any triple car valve will cause an emergency brake application. However, if brake pipe pressure is too low due to excessive amount of brake applications, emergency applications will not produce large airflow volumes for trip three valves, so engine drivers have no means of stopping the train.
Solution
Dynamic brakes
To prevent runaway due to brake pressure loss, dynamic braking (rheostatic) can be used so that locomotives will help in slowing down the train. Often, mixed braking, simultaneous dynamic brake and train applications, will be used to maintain a safe pace and keep slack at declining values. Maintenance will then be provided when removing the service and dynamic brakes to prevent mutual tooth damage caused by a sudden train jump.
Two-pip air brake
Another solution for brake pressure loss is a two-pipeline system, installed in most modern passenger stock and many freight cars. In addition to traditional brake pipes, this increase adds to the main reservoir pipe, which continues to be filled with air directly from the main locomotive reservoir. The main reservoir is where the output of the locomotive air compressor is stored, and finally the compressed air source for all the systems that use it.
As the main dams continue to be constantly suppressed by the locomotive, the car reservoir can be filled independently of the brake pipe, this is done through the valve to prevent feeding back into the pipe. This arrangement helps to reduce the pressure loss problem described above, and also reduces the time required for the brake to release, since the brake pipe only has to recharge itself.
The main reservoir pipe pressure can also be used to supply air for auxiliary systems such as pneumatic door operators or air suspensions. Almost all passenger trains (all in the UK and USA), and many freights, now have a two-pipe system.
Accident
Air brakes can fail if one of the cocks in which the pipes of each carriage join together are inadvertently closed. In this case, the brake on the cart behind the closed chicken will fail to respond to the driver's instructions. This happened in the 1953 railroad accident of the Pennsylvania Railroad involving Federal Express, a Pennsylvania Railroad train escaping when heading to Union Station Union Union, causing the train to crash into the passenger Concourse and crashed through floor. Similarly, in the Gare de Lyon train accident, the valve is accidentally closed by the crew, reducing the braking power.
There are a number of safeguards usually taken to prevent this kind of accident. The railroad has strict government-approved procedures to test the air brake system when making trains in the yard or picking up cars on the way. This generally involves connecting the air brake hoses, charging the brake system, setting the brakes and manually checking the car to ensure the brakes are applied, and then releasing the brakes and manually inspecting the car to ensure the brakes are released. Particular attention is typically given to the rearmost car of the rail, either by manual inspection or through automatic end-of-train devices, to ensure that brake pipe continuity exists throughout the carriage. When brake pipe continuity is present throughout the train, brake failure to apply or release on one or more cars is an indication that the triple car valve is damaged. Depending on the location of the air test, the available repair facilities, and the regulations governing the number of non-functioning brakes allowed on the train, the car may be set to be repaired or taken to the next terminal that can be repaired.
Standardization
The modern air brakes are not identical to the original airbrake because there are slight changes in the design of triple valves, which are not fully compatible between versions, and which must therefore be introduced gradually. However, the basic air brakes used in trains around the world are highly compatible.
European System
European air rail brakes include Kunze-Knorr brakes (created by Georg Knorr and produced by Knorr-Bremse) and Oerlikon. The working principle is the same as the Westinghouse air brake. In the steam era, British trains were divided - some using vacuum brakes and some using air brakes - but there was a gradual standardization of the vacuum brakes. Some locomotives, for example in London, Brighton and the South Coast Railway, are fitted with two so they can work with vacuum or air-braked trains. In the diesel era, the process was reversed and British Railways switched from vacuum braking to abraded braking in the 1960s.
Vacuum brake
The main competitor for the air brake is the vacuum brake, which operates at negative pressure. The vacuum brake is slightly simpler than an airbrake, with an ejector without moving parts in a steam engine or mechanical or electric "suction" on a diesel or electric locomotive replacing an air compressor. Emitting joins at the ends of the car is not necessary because the loose hose is sucked into the mounting block.
However, the maximum pressure is limited to atmospheric pressure, so all equipment must be much larger and heavier to be compensated. This loss is exacerbated at high altitudes. The vacuum brakes also work much slower both in applying and releasing the brakes; this requires a higher level of skill and anticipation of the driver. In contrast, vacuum brakes have the advantage of a gradual release long before Westinghouse's automated wind brakes, which were initially only available in direct release form that are still common in shipping services. The main fault of the vacuum brake is the inability to easily find leaks. In positive air systems, leaks are quickly discovered due to escaping pressurized air; finding a vacuum leak is more difficult, although it is easier to fix when found because a piece of rubber (for example) can only be tied around a leak and will be held firmly there by a vacuum.
Electro-vacuum brakes have also been used with great success in several units of South African electric trains. Despite requiring larger and heavier equipment as mentioned above, the electro-vacuum brake performance approached contemporary electro-pneumatic brakes. However, its use has not been repeated.
See also
- Air brake (road vehicle)
- Gladhand Connector
- Train brake footprint
References
- Brake and Air Traffic Handling Guide. Copyright 2006 Alaska Railroad Corporation
- Guide to Handling of Brakes and Air Trains. Copyright 2003 BNSF Railway Company
- AAR wheel dynamometer - braking: [1]
- Operation of Compression Operation Guide, ISBN: 0-07-147526-5, Company Book of McGraw Hill
External links
Information
- Train-Technical: Air Brake
- George Westinghouse Air Brake Patents and inventions
- How to Train You to Stop , by Bill Reiche's 1951 article with an illustration that covers the fundamentals of how a layman would understand
Paten
- US 16220 Carson Samuel: Mesin udara 1856-12-09
- US 88929 Â Westinghouse George: Tenaga uap rem 1869-04-13
Source of the article : Wikipedia
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