Page 144 - Technology Roadmap Transportation

TECHNOLOGY VISION 2035

2.4 PAYLOAD TO TARE WEIGHT RATIO OF equipment, an ECP End-of-Train device, and a
WAGONS power and communications distribution system.
Tare is the weight of an empty wagon, whereas, The locomotive equipment, referred to as the
payload is the actual useful material that can be Head-End-Unit (HEU), consists of a train-line
carried in the wagon. Tare and payload adds to communications controller, train-line power
make gross loads. Once the maximum axle load supply and an identification module. The wagon
for a particular railway is fixed, the gross weight equipment consists of the car control device,
also gets fixed. In order to have more productivity vent valve, wagon identification module and
from a wagon, higher payload to tare ratio is junction boxes. Train-line cable and connectors are
needed. This is possible by reducing the tare weight, provided on both the wagon and locomotive.
which can be achieved by using lighter wagons by
way of using suitable materials for construction. The South African Transnet Coal-line was the
first major heavy-haul operator in the world to
Indian Railways use many types of wagons, in apply ECP/WDP (wired distributed power) brake
which the ratio varies from 0.9 upto 2.6 (2.6 in technology as opposed to RDP (radio distributed
case of BOXN type)[17]. The material used for power) to its entire fleet[22].
construction is steel, which adds to the tare weight.
Indian Railways have taken up development of ECPB in wagons is a very effective way of
lighter wagons to achieve payload to tare weight improving the throughput of a train by way of fast
ratio of 3.4 by using stainless steel[18]. By using braking and release times. This is similar to the
aluminium and other composites, it can be further pneumatic braking presently used in the Electrical
improved. Multiple Units. Indian Railways may like to pursue
the ECPB technology.
In contrast, the payload to tare ratio prevalent
in the US railroad and Western Railroads are in 2.6 INTELLIGENT ADHESION CONTROL
between 3.5 to 4.5[19]. While Indian Railways SYSTEM IN LOCOMOTIVES
carry about 450 kg of dead weight for every 1,000 In rail vehicles, the torque of the motorised
kg freight, the dead weight in the US does not rotating wheel is translated to linear force and
exceed 170 kg. European Railways have already transmitted to the locomotive through friction
initiated an Innovative Rail Freight Wagon Design (normally known as adhesion) between the
2030 programme to develop state-of-the art propelling wheel and the rail, and the maximum
technology in freight carriers[20]. value is limited by the coefficient of adhesion,
which is a physical phenomenon. Hence, even
2.5 ELECTRONICALLY CONTROLLED though the locomotive may be very powerful,
PNEUMATIC BRAKES (ECPB) IN WAGONS it is not necessary that it can provide enough
Traditionally, brakes are applied from wagon to pull to the train, unless coefficient of adhesion is
wagon along the train in a sequential manner. On a favourable.
150-wagon freight train, this could take up to two
minutes between operation of the control valve On the other hand, coefficient of adhesion
on the leading locomotive and the application of varies widely depending upon the track and
brakes on the last wagon[21]. environmental conditions. A dry rail offers a better
adhesion, whereas, a wet and greasy rail offers low
In contrast, ECP braking uses electronic controls, adhesion values. If the adhesion is poor but the
which make it possible to activate air-powered locomotive generates more tractive effort, which
brakes on all the wagons throughout the train cannot be sustained through friction, the remaining
at the same time. Applying the brakes uniformly effort goes for accelerating the wheel, known as
and instantaneously in this way gives better train wheel slip. The coefficient of adhesion is the ratio
control, shortens the stopping distance, and of tractive effort at which the wheel slip occurs to
leads to a lower risk of derailment or of coupling the dead weight of the locomotive. The maximum
breakage. The ECPB can also apply the brakes on force that can be transmitted to the trailing stock-
the rearmost wagons, slightly before the brakes on T = µ*W, where µ is the coefficient of adhesion
the front wagons are applied, which reduces the and W is the deadweight of the locomotive.
shock and noise of the wagons bunching up.
Due to axle load considerations, the weight of the
The ECP brake control system consists locomotive cannot be increased beyond a point.
of locomotive equipment, wagon braking Hence, in order to derive maximum tractive force,

142 RAILWAYS