EMU brake systems


This page details the air brake equipment for electric rail car sets for EMU stock of Kolkata (Calcutta) and Mumbai (Bombay). The material has been adapted from official IR documentation. Also see: Vacuum and air brake systems

General

There are two different types of formations of electric rail car in use at present in India. These are:

  • 4-car formations for AC EMU stock
  • 3-car formations for DC EMU stock

AC EMU Stock

Electric rail cars in A. C. EMU cars normally consist of 4 cars, 2 driving trailers, 1 motive power unit and 1 plain trailer. These cars are connected by automatic coupling in the following order:

  • Driving Trailer
  • Motive Power Unit (Motor Coach)
  • Plain Trailer
  • Driving Trailer

DC EMU Stock

The train formations of DC EMU stock normally consist of 3 cars, 1 driving trailer, 1 Motor Coach and 1 Plain Trailer connected in the following order:

  • Driving Trailer
  • Motor Coach
  • Plain Trailer

The driving trailer and the motor coach each have one driver's compartment. The compressed air required for the brake system and various auxiliary equipments is supplied by compressor mounted in the motor coach.

The rail-car sets are equipped with self-lapping electrically controlled Escorts - Knorr airbrake Kbr VIII - C1. List of items supplied to ICF for control and brake equipment for Motor Coaches/Plain Trailers are mentioned in Annexures A and B respectively. The electric cable connections have also been shown as per drawing ENSKV 37777, ENSKV 37778 and ENSKV 30803

Arrangement of Brake Apparatus

The part numbers given refer to the general assembly drawings.

The compressed air required for the four-car train set is provided by a compressor which is not supplied by Escorts and stores in the main air reservoirs. There are two main air reservoirs in each driving trailer and in the trailer and one in the motive power unit. These reservoirs are connected by means of the coupled main air reservoir pipe which runs throughout the train set. The main air reservoirs are fitted with drain cocks for draining off the condensate which forms there.

In addition to the main air reservoir pipe, the automatic brake pipe is also coupled throughout the train set. This is done in both cases by means of the automatic coupling with which all the cars are fitted. The through pipes are equipped with isolating cocks and hose connections in front of the couplings. Before uncoupling any car, the appropriate isolating cocks must be closed.

Both the electrically controlled and automatic air brakes are operated by means of the brake controller. This works in conjunction with the EP brake unit. There is a brake controller in each driver's compartment. Thus the driving trailers and the motive power unit each have a brake controller. Every car, however, hence also the trailer, has an EP brake unit. The brakes of the whole train are operated from one of the brake controllers. For this purpose, electric cables are also connected throughout the train like the air pipes.

Pipe line air filters with drain cocks are fitted in the main air reservoir pipe at the junctions of the branch pipes leading to the brake controllers. The purpose of these filters is to prevent water and possibly other impurities from entering the brake controllers. In addition, the brake controllers are connected by a pipe to the through automatic brake pipe.

A duplex pressure gauge and a single pressure gauge are mounted near the brake controller in the driver's compartment. The former indicates the pressure in the main air reservoir pipe and in the automatic brake pipe while the latter shows the pressure in the brake cylinders.

The EP brake unit through which, depending on the pre-controlling action of the brake controller, air is admitted to or exhausted from the brake cylinders is connected to the main air reservoir pipe as well as to the automatic brake pipe. In the through air pipes, pipe line filters with drain cocks are provided at the junction of the branch pipes for the separation of condensate.

Isolating cocks are fitted in the supply pipes leading to the EP brake unit. These isolating cocks may be used in the evenmt of a defect occurring in the EP unit to cut off the air supply. An auxiliary air reservoir is connected to each EP brake unit. In this reservoir, the compressed air required to fill the brake cylinders on operation of the automatic air brake is stored.

A release valve is fitted in the brake cylinder pipe leading to the bogies on every car. By means of this release valve, the brake cylinders of each separate car can be directly exhausted.

Isolating cocks are provided in the brake cylinder pipe leading to the bogies. In the event of failure of the brake in one of the bogies, for instance rupture of a hose connection, the pipe leading to that bogie can thus be closed while the brake continues to operate in other bogie.

The passage of the brake cylinder pipes from the frame to the bogies is effected by means of hose connections.

The brake cylinders are equipped with automatic slack adjusted. In the motive power unit, each bogie has 4 brake cylinders while the bogies of the driving trailers and the trailer each have 2 brake cylinders. In the driving trailers, one brake cylinder beneath the driver's compartment is fitted with a hand-brake connection. The different number of brake cylinders required is due to the different weights of the cars.

In view of the slight pivoting motion allowed by the mounting of the brake cylinders, hose connections are used for the brake cylinder pipe.

A pressure governor is mounted in each bogie. This pressure governor serves to indicate to the driver by means of an electric signal whether the pressure in the brake cylinders is higher than 0.5 kg/cm2 (7psi).

In the trailer, the brake cylinder pressure is indicated by a pressure gauge in the brake cylinder pipe on the underframe.

Each driver's compartment is equipped with an emergency brake valuve, by means of which the automatic brake pipe can be directly exhausted in case of emergency. In addition, a pressure gauge connected to this emergency valve indicates the pressure in the automatic brake pipe.

A dead-man valve is connected in the pipe between the brake controller and the through, automatic brake pipe. An isolating cock is fitted in front of the dead-man valve. The dead-man valve is acted on by the master controller.

For the supply of air to auxiliary air-pressure equipment such as signalling apparatus and windscreen wipers, the driving trailers and motive power unit each contain 1 air reservoir which is fed from the main air reservoir pipe via an overflow valve. This air reservoir is fitted with a drain cock for the separation of condensate.

Both the driving trailers and the trailer are equipped with a signalling device consisting of multi-tone horn. It is actuated by a foot-operated valve. An air cleaner and an isolating cock are connected in the foot-valve. The windscreen wiper installation is not supplied by Knorr/Escorts.

Pressure governors are connected to the automatic brake pipe in the automatic coupling at the end of the driving trailers and the motive power unit which contains the driver's compartment. These pressure governors are used to establish the connection from the positive cable to the indicator cable (see electric wiring diagram).

In the motive power unit, a pressure governor is provided in the automatic brake pipe. This pressure governor serves to prevent starting; that is to say, as long as the pressure in the automatic brake pipe is below a specified value, the motive power unit cannot start to move, for at any pressure below 4.2 kg/cm2 (60psi) an electric contact is broken.

Method of Operation

The air delivered by the compressor flows through the coupled main air reservoir pipe to the man air reservoirs in the different cars, where a pressure of 6-7 kg/cm2 (85-100psi) builds up. At the same time, the air flows through the centrifugal filters to the brake controllers.

The whole train is controlled from one driver's compartment. In this manned driver's compartment, the hand-operated isolating valve on the brake controller must be opened with the detachable handle. This establishes the electrical connections required for operation of the electrically controlled airbrake.

In the unmanned driver's compartments the hand-operated isolating valve on the brake controller must be closed. Only one handle for turning the isolating valve should be available in each train. Since this handle is required for the brake controller which is in operation and it can only be removed when the isolating valve is closed, it follows that the isolating valves in the unmanned driver's compartments must be closed. The driver's handle of the brake controller in the unmanned driver's compartments must be in running position.

In the manned driver's compartment, in running and release position the brake controller establishes communication between the main air reservoir pipe and the automatic brake pipe and the latter is filled with compressed air. The method of operation of the brake controller is described in detauk ub Description B 1598 e. Air pressure flows through the automatic brake pipe via the centrifugal filters and the isolating cocks to the EP brake units and fills the auxiliary reservoir connected to each EP unit.

The EP brake unit is described in Description B 1595 e. The pressure in the automatic brake pipe and in the auxiliary reservoirs in the full release position is 5 kg/cm2 (71psi).

Compressed air is also supplied to the EP brake units from the through main air reservoir pipe via the centrifugal filters and the isolating cocks.

In order to initiate an electrically controlled application, the driver's handle of the brake controller should be moved a little way in the direction of the full application position. This causes electric contacts in the three-pressure switch of the brake controller to close. The resulting electrical impulses are transmitted via the holding and application relay and the through cable connection to the magnet valves in the EP brake units. The magnet valves are energised and compressed air flows from the main air reservoir pipe via the EP brake units into the brake cylinders, where a specified pressure is built up. Each position of the driver's brake handle between running position and full application position corresponds to a specified brake-cylinder pressure; the further the handle is moved towards full application position, the higher the pressure produced. In full application position, the maximum brake-cylinder pressure of 3.6 kg/cm2 (52psi) is reached. If, to release the brakes, the driver's handle is moved back a little towards running position, the electrical impulses are again transmitted to the EP brake units by the three-pressure switch. This causes air pressure to flow out of the brake cylinders to atmosphere through the EP units until the cylinder pressure has fallen to the value corresponding to the selected handle position. The further the handle is moved back towards running position, the lower the brake-cylinder pressure become. In running position the brake cylinders are fully released. Hence it is possible to obtain graduated application and release with the electrically controlled air brake.

In the event of failure or interruption of the operating current for the electrically controlled brake, the automatic air brake immediately becomes available and is regulated within the same brake handle range as the electrically controlled brake. On operation of the automatic air brake, the pressure in the through brake pipe is reduced on the application of the brake in accordance with the handle position selected. The pressure reduction acts on the triple valve in the EP brake units, through which the auxiliary reservoirs are connected to the brake cylinders. Depending on the degree of pressure reduction, a corresponding pressure rise is produced in the brake cylinders. By reducing the pressure can be increased step by step, until, in the full application position, the maximum brake cylinder pressure is reached. This is limited by a safety valve in the EP brake unit to 4.0 kg/cm2 (57psi). When the handle is moved back towards running position, for release, the pressure in the automatic brake pipe is raised again, whereupon the brake cylinders are fully exhausted. Thus graduated release is not possible when using the automatic brake.

During release, the auxiliary reservoirs are simultaneously re-charged with air-pressure from the automatic brake pipe.

In the emergency application position the automatic brake pipe is rapidly and directly exhausted via the brake controller, so that when the electrically controlled brake is in operation the automatic airbrake also come into action. Thus rapid controller in conjunction with the EP brake unit is described in full detail in description B 1578 e.

The dead-man valve is connected to the automatic brake pipe. In the event of incapacitation of the driver, this valve serves to connect the automatic brake pipe to atmosphere so that brake application is initiated. The precise method of operation of the dead-man valve is described in Description B 1299 e. In the unmanned driver's compartments, the isolating cocks in front of the dead-man valves must be closed, thus putting the valves out of action.

The air reservoirs for the auxiliary equipment are supplied with air from the main air reservoir pipe, via the overflow valves. The overflow valves are set for 5kg/cm2 (71psi). This means that as soon as the pressure in the main reservoir pipe exceeds this value, the reservoirs are filled. The overflow valves are designed to allow back flow. If the pressure in the main reservoir pipe drops below that in the reservoirs, air-pressure flows back from these, through the overflow valves.

Material provided by S Krishnamorthy, Copyright 2002.
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