AIR BRAKE SYSTEM

Air Brake System is defined as the air as a medium using pressure of a compressed air a force will be exerted at the brake shoes by mechanical leverages so that member can be stopped.

In railways, an air brake system is a type of braking system used to slow down and stop trains. It operates on the principle of compressed air to control the brakes on individual railcars or wagons throughout the entire train.

In the air brake system, a lot of developments have taken place such as bogie mounted Air brake system, Twin pipe air brake system, Automatic load sensing device etc.. As a result, the maintenance and requirements have changed considerably.

Recently, Bogie mounted Brake System (BMBS) has also been introduced for freight stock. The details of BMBS for freight stocks are given in this seminar.

In India AAR is followed in railway system

Types of Braking System:

• Mechanical Brake System.

• Hydraulic Brake System.

• Vacuum Brake System.

• Air Brake System.

CLASSIFICATION OF AIR BRAKE SYSTEM:-

On the basis of type of release, Air brake system is classified as:

1. Direct release air brake system.

2. Graduated release air brake system.

Both Direct and Graduated release are further available in two forms viz.

1. Single pipe and

2. Twin pipe

On the basis of type of fitment, air brake system is classified as:

1.Under frame mounted air brake system.

2.Boige mounted air brake system.

Air brake system consists of following components:-

• Distributor valve

• Common pipe bracket with control reservoir.

• Auxiliary reservoir.100 Litres & 75 Liters

• Three way centrifugal dirt collector.

• Isolating cock.

• Brake cylinder 355mm diameter & 300 mm diameter.

• Cut off angle cock (32mm size on either ends of brake pipe & feed pipe).

• Air brake hose coupling (32mm for brake pipe / 32 mm from feed pipe).

• Brake pipe/feed pipe (32mm dia).

• Branch pipes from BP to brake equipment (20mm bore).

• Guard emergency brake valve.

• Pressure gauges for BP

• Quick Coupling

Advantages of Air Brake System:

• Higher braking force for longer, heavier and faster trains.

• Shorter braking distance.

• Simple brake rigging.

• Uniform brake power over train length.

• Reduced brake power deterioration.

• Suitable for all terrain working.

• Faster application and release

• Better control over the train.

Direct Release System:

• Used in American Rail road where DV does not allow the BC pressure to be released in stages.

• Once BC starts to exhaust, it will do so till BC pressure becomes zero.

• This will affect the BC pressure during subsequent applications. (Not suited for that sections)

Graduated Release System:

• DV will allow BC pressure to be reduced in stages.

• This helps in retaining air pressure in BC during subsequent brake applications.

• This system is adopted in Indian Railways.

WORKING PRINCIPLE:

Whenever a drop in pressure in the system happens then the brake gets applied

The processes involved in working of graduated release air brake system are:-

• CHARGING STAGE.

• APPLICATION STAGE.

• RELEASE STAGE.

Air brake system is further classified as;

• Single pipe System:- Only brake pipe is provided for charging the AR and for Brake application.

• Twin pipe system:- Brake pipe is provided for DV operation. Feed pipe for charging Auxiliary Reservoir.

Principle Of Operation Of Single Pipe Graduated Release Air

BRAKE SYSTEM.

Some of the Air Brake goods stock on IR is fitted with single pipe graduated release air brake system. In single pipe, brake pipes of all wagons are connected. Also all Handbook on Air Brake system for Freight stock 2 CAMTECH /GWL Feb. 2012 the cut off angle cocks are kept open except the front cut off angle cocks of BP of leading loco and rear end cut off angle cock of BP of last vehicle. Isolating cocks on all wagons are also kept in open condition. Auxiliary reservoir is charged through distributor valve at 5.0 kg/cm2 .

Working Principle Stages

1. CHARGING

2. APPLICATION

3. RELEASE

4. MANUAL RELEAASE

• MANUAL RELEASE

When engine is cut off from the train or wagon/vehicle brakes will apply automatically due to reduce/venting of BP pressure. When the train brakes are required to released for some reasons it should be done by pulling quick release valve (QRV) of DV which in turn venting CR pressure to Atmosphere and positioned the DV in such a way that the AR is isolated from BC and BC is connected to exhaust and the brakes will be released.

• CHARGING STAGE:

During this stage, brake pipe is charged to 5kg/cm² pressure which in turn charges control reservoir and auxiliary reservoir to 5 kg/cm² pressure via distributor valve. At this stage, brake cylinder gets vented to atmosphere through passage in Distributor valve.

• APPLICATION STAGE:

For application of brakes, the pressure in brake pipe has to be dropped. This is done by venting air from driver's brake valve. Reduction in brake pipe pressure positions the distributor valve in such a way that the control reservoir gets disconnected from brake pipe and auxiliary reservoir gets connected to brake cylinder. This results in increase in air pressure in brake cylinder resulting in application of brakes. The magnitude of braking force is proportional to reduction in brake pipe pressure.

NOTE: -

1. Brake Application takes places when Brake pipe pressure is dropped.

2. The drop of pressure may be Intentional and by Accidental.

During this stage, brake pipe is charged to 5kg/cm² pressure which in turn charges control reservoir and auxiliary reservoir to 5 kg/cm² pressure via distributor valve. At this stage, brake cylinder gets vented to atmosphere through passage in Distributor valve.