What kinds of brake systems do IR coaches and freight cars have?

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What kinds of brake systems do IR coaches and freight cars have?

July 16, 2019, 1:25 PM

In older stock, both passenger coaches and freight wagons, the continuous braking system consists of vacuum brakes. Newer stock is almost always air-braked. The guard often has mechanical brakes acting on his van. In addition, each piece of stock has mechanical parking brakes.

Continuous brakes were tried out by the various railway companies in the late 19th century. North Western Railway was the pioneer with trials of continuous vacuum braking in the late 1880s and early 1890s. Vacuum brakes were chosen for the simplicity of design and lower cost. They also did not have coupling cocks that could fail mid-train.

Early examples of the use of air brakes on IR include the Metro Cammell EMU stock delivered between 1951 and 1953 (and similar stock later delivered by other manufacturers), which featured the Westinghouse twin pipe air brake system and electro-pneumatic application (the 1924 and 1928 EMUs (CR and WR) were vacuum-braked). In the 1960s, the Deluxe Exp. (25 Down) and the Frontier Mail (3 Down) are also said to have had air brakes of the graduated-release kind. (This information has not been verified — it’s likely that the Bombay Rajdhani was in fact the first long-distance train with air-brakes, which it acquired in 1984.)

However, these were isolated examples and air brakes did not come into wide use until some time beginning in the late 1970s and the early 1980s. Perhaps the most notable ‘convert’ of the time was the Mumbai Rajdhani which switched to being air-braked in 1984, hauled by twin WDM-2 locos. The Howrah Rajdhani also switched to being air-braked around 1986. Many express trains were vacuum-braked until very recently (e.g., Madras-Howrah Coromandel Exp. was vacuum-braked until 1997.)

Air-braked rakes are now very common. Generally the blue-coloured livery that is now common on IR for passenger coaches indicates air-braked stock. The air brakes are mostly of the twin pipe system, with a feed pipe and a brake pipe. Air-braking (with dual pipes) is now standard for all Rajdhani/Shatabdi and most other high-speed trains. (The twin pipe system fixes a problem with the single-pipe system where the air in the auxiliary reservoir can be used up faster than the brake pipe can charge it.)

On the broad-gauge network, only a few passenger trains running on low-speed lines are now left with vacuum-braked stock, and most of these are being converted to air brakes rapidly. In some cases, as with the Sahyadri, Maharashtra, and Koyna Expresses which were vacuum-braked until [2/02], there was no convenient shed nearby for maintenance of air brakes (Kolhapur at the time did not yet have the required facilities). These trains have been converted to air brakes now [12/04], as has the Dakshin Express most recently, a vacuum-braked holdout for a very long time.

The Viramgam Passenger is still vacuum-braked [1/05], the only train out of Mumbai Central now. The Tatanagar Passenger had 3 vacuum-braked rakes until recently [5/05]. The international Samjhauta Exp. is another notable passenger train with vacuum brakes. The Toofan Exp. and the Bokaro/Tatanagar – Alleppey Exp. may also be air-braked (uncertain) [12/04].

As of [5/04], about 7910 passenger coaches were vacuum-braked (out of the total fleet of 40,000 coaches). It is expected that the entire fleet will be converted to air brakes by March 2006 (about 4080 to be converted in the fiscal year 2004-2005). Most MG and NG coaches are still vacuum-braked, though. (The MG EMUs that ran in Chennai until 2004 were also vacuum-braked.)

Dual-braked passenger coaches are rare, but some do exist, including sleeper coaches and AC 3-tier coaches; most of these are not for general use but are saloons, inspection cars, or officer’s cars, which may need to be attached to either air-braked or vacuum-braked rakes.

With later freight stock (often colored green) single-pipe or dual-pipe air braking is becoming standard. But there is still a lot of freight stock that is vacuum-braked. Much older freight stock is being retrofitted with air brakes –– the workshops at Lallaguda (SCR), Parel (WR), and Matunga (CR), among others, undertake such conversions.

Air brakes are among the most significant changes undertaken by IR in recent decades. They have allow much higher speeds on most sections as trains can be safely braked in a shorter distance, leading to better track utilization. Earlier, for instance, it was standard practice to begin braking at an Attention signal (double yellow); now most trains speed past an Attention signal at the highest permitted speed and begin braking only when a Caution signal is sighted. Safety has also increased with the power and precision of air brakes.

Changing locomotives is now a matter of minutes – the angle cocks are closed, the locomotive is detached, the new one attached and the cocks are opened once again. Earlier, disconnection of the vacuum hose meant that all the brake pistons under the coaches went into emergency mode and had to be manually released (by pulling a wire loop — usually marked with a star — under the coach). The process of releasing the brakes easily takes around 15 minutes for vacuum-braked stock. On the other hand air brakes do require more precise maintenance and care.

The standard BCN/BOXN/BPTGLN/etc. wagons have frame-mounted cylinders for the brakes, as do the passenger coaches. Bogie-mounted brakes are only now [4/00] being introduced on passenger coaches from ICF and RCF, and also being retrofitted on older passenger stock in some zonal railways.

BG EMU rakes have electro-pneumatic (‘EP’) brakes which are essentially air brakes, but where the application is controlled electrically at each brake unit. BG EMUs have had air brakes for many decades (see above). MG EMUs of the Chennai system were vacuum-braked. DMU rakes have standard twin-pipe graduated release air brakes.

Brake blocks used to be made of cast iron. Later, various other materials were brought into use, including asbestos-based materials. More recently [4/01] RDSO has developed new kinds of asbestos-free composite materials for use in brake blocks. These are known as the ‘L’ type brake blocks and after being introduced for BG have also been recently [2005] introduced for MG stock.

Source – IFRCA.org

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