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

y the driver’s vacuum brake valve.
c) Air admission valve (B8), attached to the train pipe and
d) Timing chamber (B22) to control sensitivity of air admission valve, controlled
by the driver’s vacuum brake valve.
e) Timing chamber to control sensitivity of air admission valve controlled by
conditions in the equalising reservoir (B20).
The exhausters (B1) with standard auxiliaries such as filter/strainer, non-return valve,
vacuum relief valve, etc. are directly connected to the train pipe through 2 inch exhauster cut out
valves, solenoid operated for vacuum creation and destruction. These cut out valves are energised
to isolate the exhausters when the handle on the Driver’s vacuum brake valve is moved towards
'brake on' but one exhauster always remains in communication with train pipe through a small bypass
in exhauster cut out valve (VA-1 release valve) B6 and with the small equalising reservoir.
With the further movement of DVB of graduated application zone, i.e. towards 'brake on' the
atmospheric air is admitted to E.Q. reservoir at a faster rate with more port opening in DVB, but
the size of the connection of E Q. reservoir to exhauster remains unaltered. With result a balance
is set up between air admitted and air extracted for each position of DVB. The progressive
reduction of vacuum in E.Q. reservoir to the required value operates the air admission valve
diaphragm to admit atmospheric air directly into the train pipe. This action is quite automatic and
over braking due to leakages in vacuum system/train pipe is compensated by continuous
extraction of air from train pipe through by-pass hole in VA-1 release valve. A small timing
chamber regulates the rate of fall of train pipe vacuum independent of rate of DVB handle
movement.
a) During emergency application of DVB, atmospheric air is also supplied by
DVB directly through 2" diameter pipe in addition to the air admission valve to
destroy vacuum at the quickest possible rate.
b) For a partial release DVB handle is returned to full release position until the
desired restoration of vacuum has taken place in T.P. and then it is only
necessary to keep DVB in suitable notch to maintain desired vacuum level.
c) The operation of emergency (flap type) valve directly connects the train pipe to
atmosphere through 2" diameter opening thereby applying brakes on loco and
trailing stock at the quickest possible rate and shuts off exhausters in addition to
regression.
d) The main reservoir also supplies compressed air to control equipment such as
horns, wipers, pantograph, auxiliary circuit but at the time of initial energisation
when there is insufficient pressure in control /emergency reservoir to raise the
pantograph, the auxiliary compressor (battery operated) is started to raise the
pressure in auxiliary circuit to energise the locomotive,
7.1.5 Setting of different valves of Vacuum brake system
Driver's independent self-lapping : 3.5 ± 0.1 kg/cm²