Traction Rolling Stock - Indian Railways Institute of Electrical ...

When the brake valve handle is moved from release position towards application position, the
brake pipe pressure and vacuum in VTP is reduced and maintained to a value depending on the
handle movement.
The reduction in brake pipe pressure operates the VA-1B control valve to admit
atmospheric air into the vacuum train pipe, to apply brakes on the vacuum braked trailing stock.
During application, the exhauster connection with the vacuum train pipe is cut off by the VA-1B
control valve. After the desired degree of brake application has taken place, depending upon the
extent of brake pipe pressure desired, the valve laps and maintains automatically the vacuum level
against normal vacuum train pipe leakage.
When the driver feels that it is not necessary to apply brake on a loco, the brake release
pedal switch is pressed to release the loco brakes. The D-l air pilot is energised to cut off
automatic air brakes on the loco while train brakes remain applied on the trailing stock.
During train parting while hauling vacuum braked stock, the vacuum in the train pipe
falls suddenly, with a drop of vacuum by about 10 to 15 cm an unbalance in the VA-1B control
valve is created allowing controlled air pressure to actuate HB-5 relay air valve to operate pressure
switch through double check valve for regression of power.
7.2.7 Operation of emergency brake (Ref. fig. 7.2.4)
D-l air pilot provided in each cab, near the assistant driver's seat directly connects the
vacuum train pipe and air brake pipe to atmosphere thereby applying brakes on loco and trailing
stock at the quickest possible rate. The circuit for auto regression of the loco power due to the
actuation of H-5 relay air valve is also automatically made. This relay valve also regresses power if
the BP pressure drops due to any reason.
7.2.8 Dynamic brakes
D-l pilot air valve cuts off loco brakes.
While controlling the train with dynamic brakes, if the dynamic brake fails, brakes on the
loco and train will be applied automatically.
7.2.9 Air flow indicator
Air flow indicator, a relay valve, one pressure switch and two flow indicator gauges (one
in each cab) have been provided to give an indication of the air flow rate in the brake pipe of the
train. Any abnormal increase in air flow in the brake pipe because of train parting, loco parting,
alarm chain pulling, heavy leakage in brake in brake pipe, guard valve application or bursting of air
brake pipe hose will give visual indication to the driver by air flow gauge needle and by glowing of
a bulb in the cab. On getting the indication driver shall apply brakes through A-9 automatic brake
valve/D-l air/vacuum emergency valve depending upon the condition of the train and the
emergency.
7.2.10 Operation of brakes during multiple unit operation of locos (Ref. fig.7.2.8)
When the locos are connected for multiple unit operation following pipes should be
connected to each other and the angle cocks of these pipes to remain open at the coupled end
closed on the free end.