Abstract - The vacuum brake was, for many years, used in place of the air brake as the standard, fail-safe, train brake used by railways. Pneumatic braking. The vacuum braking system was developed from above said reasons and the the Vacuum brake system i.e., the loss of vacuum will cause the brake to be. GENERAL DESCRIPTION. a Vacuum brake system has been improved gradually over the years by increasing the brake rigging ratio, effecting modifications.
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TM B, Ordnance Maintenance, Vacuum Brake Systems. (Bendix B-K), is published for the information and guidance of all concerned. [A.G. (23 Sept . Explore Vacuum Braking System with Free Download of Seminar Report and PPT in PDF and DOC Format. Also Explore the Seminar Topics. Vacuum Braking System, Ask Latest information, Vacuum Braking System Abstract,Vacuum Braking System Report,Vacuum Braking System Presentation ( pdf.
Twin Pipe System Twin pipe vacuum systems were standard on the 1st generation British Rail Diesel Multiple Units which replaced steam locomotive hauled passenger trains on many branch and secondarylines in the s. Another version of the vacuum brake used two train pipes. The usual brake pipe operated in the conventional way but the second pipe was provided to give an additional supply to speed up the brake release.
The second pipe is called the reservoir pipe. The diagram below shows a schematic of the system, with the reservoir pipe shown in grey. The two-pipe system was introduced on diesel railcars where the exhauster was driven directly off the diesel engine.
Since the engine was only idling if the train was stationary, the exhauster would only be running at slow speed.
This meant that the restoration of the vacuum in the brake pipe and cylinders along the train would be very slow. To get a rapid brake release when it was needed to start the train therefore, a "high vacuum" reservoir was provided on each car, the reservoirs being supplied from a second train pipe called the Reservoir Pipe.
These additional reservoirs were characterised by their operating vacuum of 28 Hg, as opposed to the 21 Hg used in the brake pipe and brake cylinders. While the train is moving and the driver's brake valve is in the "Running" position, the exhauster is connected to the reservoir pipe and through the driver's brake valve to the brake pipe.
An automatic feed valve fitted between the reservoir pipe and the driver's brake valve limits the maximum vacuum passing to the driver's brake valve at 21 Hg.
This means that the vacuum in the brake pipe and brake cylinders will be limited to 21 Hg. However, the vacuum created by the exhauster in the reservoir and high vacuum reservoirs will reach 28 Hg, as shown in the diagram above in grey. To apply the brake, "Brake On" is selected by the driver and the brake pipe is opened to atmosphere at his brake valve.
The exhauster will continue to run and maintain the 28 Hg reservoir level. The connection to the feed valve is closed by the driver's brake valve when it is in the "Brake On" position A partial application can be made by moving the handle to "Lap". There is no "Release" position.
As soonas "Running" is selected, the connection to atmosphere is closed and the connection to the feed valve and exhauster opens to start restoring the vacuum. As there is a storeof "high" vacuum available in the reservoir pipe and reservoirs, the process is speeded up to give a rapid release.
Each reservoir has an automatic isolating valve between itself and the brake pipe. This valve is set to 19 Hg and closes if the vacuum in the reservoir falls below this level. This has the effect of preventing the reservoir from being emptied. The volume of the reservoir is such that it can restore the vacuum for several applications and releases before it drops below 19 Hg.
If a partial application is required on a long train, a good deal of skill is required to estimate how much air to let in or let out on an air braked train to get the application wanted.
To help set the brake to the right level, some vacuum brake systems have an equalising reservoir. This is fitted between the driver's brake valve and the brake pipe and it acts in conjunction with a relay valve or "air admission valve". When the driver moves the brake valve to the "Brake On" position, air is admitted into the equalising reservoir, not directly into the brake pipe.
He monitors the lowering of the vacuum using the gauge provided in the cab. The reduction of vacuum causes the air admission valve to open the brake pipe to atmosphere.
When the vacuum level in the brake pipe has fallen to the level set in the equalising reservoir, the air admission valve closes to maintain the brake pipe vacuum at that level. The main advantage of the equalising system is that it allows the driver to select a level of brake quickly, using the small volume of the equalising reservoir instead of having to wait for the level along a whole train's length of brake pipe to settle before he knows what the real level is. In a dual fitted vehicle, there would be both a vacuum cylinder and one or more air brake cylinders, all operating on the same set of rigging to apply the brakes at the vehicle wheels.
Some of BR's Mk1 coaches were built with dual brakes all had vacuum as standard and much of the rest of the fleet was dual fitted by the s, so they could be worked by air or vacuum fitted locomotives as the changeover from vacuum to air took place between and the early s.
On a smaller vehicle such as a traditional four-wheeled goods wagon, it is much easier to fit just one kind of brake with a pipe for continuity of the other.
Train crew need to take note that the wrong-fitted wagons do not contribute to the braking effort and make allowances on down grades to suit. Many of the earlier classes of diesel locomotive used on British Railways and electric locos up to and including the Class 86 were fitted with dual systems to enable full usage of BR's rolling stockinherited from the private companies which had different systems depending on which company the stockoriginated from.
Air brakes need a tap to seal the hose at the ends of the train. If these taps are incorrectly closed, a loss of brake force may occur, leading to a dangerous runaway. With vacuum brakes, the end of the hose can be plugged into a stopperwhich seals the hose by suction. It is much harder to block the hosepipe compared to air brakes.
The principle of operation was the same as for other type of train but there were some differences as described below. They are, of course, steam operated. The ejector consists of a series of cones inside a tube.
Steam is allowed to pass through the cones so that a vacuum is created in the tube and thus in the brake pipe to which it is connected. The large ejector provides the rapid build-up of vacuum required for brake release and the small ejector provides the constant vacuum needed to keep the brake pipe and cylinder vacuum at the correct level to maintain brake release.
On some locomotives, ejectors were combined with the driver's brake valve. Most had only "Brake On", "Running" and "Brake Off" positions and many were combined with a steam brake fitted to the locomotive and tender. The more sophisticated allowed a single brake application to apply the brakes on the train before they were applied on the locomotive.
This gave a smoothand even stop and prevented "bunching" of coaches behind the locomotive. Drivers were taught that it was best to slow the train down and then gently ease off the brakes as the train came to a stop.
This required them to restore much of the vacuum by the time the train was brought to a stand, allowing a quick release without having to run the large ejector for very long, thereby saving steam. Air brakes required a steam-powered compressor - bulky, noisy, and unsightly and using a lot of power, while the vacuum ejector used to generate vacuum was a much simpler device.
It has the advantage of being simple in design and of having the ability to get a partial release, something the air brake could not do without additional equipment. Journal of the Irish Railway Record Society. June Indian railways. Railway webpages. You just clipped your first slide! Vacuum brake Presented By: Presentation OfVacuum brake Table of Contents: Project Details Project Name: Overview of Vacuum brake History- The vacuum brake is a braking system employed on trains and introduced in the mids.
A variant, the automatic vacuum brake system, became almost universal in British train equipment and in those countries influenced by British practice.
Overview of Vacuum brake: Overview of Vacuum brake It was an alternative to the air brake, known as the vacuum brake. Like the air brake, the vacuum brake system is controlled through a brake pipe connecting a brake valve in the driver's cab with braking equipment on every vehicle.
Parts of the Vacuum Brake System: Exhauster- A two-speed rotary machine fitted to a train to evacuate the atmospheric pressure Brake Pipe- The vacuum-carrying pipe running the length of the train Dummy Coupling- At the ends of each vehicle Coupled Hoses- The brake pipe is carried between adjacent vehicles through flexible hoses Parts of the Vacuum Brake System: Brake Block - made of cast iron or some composition material Brake Rigging - the movement of the brake cylinder piston transmits pressure to the brake blocks on each wheel Ball Valve -needed to ensure that the vacuum in the vacuum reservoir is maintained at the required level How the automatic vacuum brake works: How the automatic vacuum brake works Vacuum brake cylinder in running position: How the automatic vacuum brake works Air at atmospheric pressure from the train pipe is admitted below the piston, which is forced up Present-day use of vacuum brakes: Present-day use of vacuum brakes Today's largest operators of trains equipped with vacuum brakes are the Railways of India and Spoornet South Africa , however there are also trains with air brakes and dual brakes in use.
Thank you……. Follow us on: Go to Application. US Vaccum braking 1. With no vacuum, at normal atmospheric pressure in the brake pipe, the brake is fully applied. In order to ensure there is always a source of vacuum available to operate the brake, a vacuum reservoir is provided on, or connected to the upper side of the piston.
It is connected between vehicles by flexible hoses, which can be uncoupled to allow vehicles to be separated. Typical vacuum brake cylinder 8. At the same time, atmospheric pressure acts on the rear side of the piston to exert a powerful pull on the rod attached to the piston. The piston is at the bottom of the brake cylinder. Note how the brake cylinder is open at the top so that it is in direct connection with the vacuum reservoir. As the air enters the ball valve, it forces the ball in red in the diagram above upwards to close the connection to the vacuum reservoir.
It was also slow to release and requires additional equipment to speed up its operation. You just clipped your first slide! Clipping is a handy way to collect important slides you want to go back to later. Now customize the name of a clipboard to store your clips.
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