INDIAN RAILWAYS – AUTOMATIC BRAKES
AUTOMATIC BRAKES
In release position of A-9 automatic brake valve, main reservoir air flows to the regulating portion of A-9 automatic brake valve at a predetermine pressure i.e. 5kg/cm2. The regulated air pressure flows through MU-2B valve to the C2W relay valve which in turn connects main reservoir air to charge brake pipe and its connected system to the same pressure even through out the train. The air brake pipe pressure can be adjusted by adjusting the regulating portion of automatic brake valve. Any leakage with limits in the B.P. System of train of automatically compensated by C2W relay valve.
When the auto brake valve handle is moved to minimum reduction position, the B.P. Stabilized between 4.3 to 4.5 kg/cm2 and proportional application of brakes on loco and train take place. In full service application of A-9 automatic brake valve handle. The B. P. pressure stabilizing between 3.4kg/cm2 to 3.6kg/cm2 over reduction is 3 kg/cm2.
DV: Distributor Valve
LV : Limiting Vlave
BKIV : Braking Isolation Valve
MR : Main Reservoir
BC : Brake Cylinder
BP : Brake Pipe
When automatic brake valve handle is placed in emergency position, the brake pipe pressure is vented to atmosphere at a very fast rate to initiate an emergency brake application. Power cutoff also takes place due to sudden drop of B.P. pressure which actuates H-5A rekay valve to supply main reservoir to peodynamic switch.
The C2W distributor valve provide in the brake circuit, connected to the air brake pipe response is the variation of pressure in the brake pipe actuates the distributor valve on loco and trailing stock to apply brakes. Due to the pressure reduction in brake pipe, the pressure also drops above the C3W valve main diaphragms. The control
Reservoir pressure which remains constant acts below on main control diaphragm of Distributor valve, move upwards to connect reservoir air to take cylinder to apply brakes. The maximum brake cylinder pressure supplied by C3W limited to 3.5 kg/cm2 by limited valve. The C3W distributor itself is having a built in goods/passenger change over cock whose handle position can be changed depending on the type of trailing stcok being hauled by the locomotives.
In WDM2 locomotives with 28LAV-I brake system fitted with 6CD. 4UCIKE-6 expresser is used in WDM-2B loco with pure air IRAB-I brake system, if these expressers are used the exhauster portion of expresser would work continuously but with our creating vacuum in the locomotive brake system. Incase the exhauster works continuously at very high vacuum, the cylinder get heated up. To avoid over heating of exhauster portion of expresser GD-80-8 filter is provide with 50min diameter x 100mm long steel pipe with 105mm diameter choke to so that vacuum level in exhauster portion of expressers may remain below 56cm.6’.1” Feed pipe through out the train is charged from fist main.
Reservoir through duplex check valve and D-24-3 feed valve set at 6.0 to 0.1 kg/cm2 and is used for filling auxiliary reservoirs of trailing stock.