CE2303 Railway Engineering Points and Crossings CE2303 Railway Engineering

Definition Points & crossings are devices or arrangement by which different routes either parallel or diverging are connected and afford the means for trains to move from one route to another.

Parallel Routes @ Station

Diverging Route

Definition These connections are not only useful for trains to move from one route to another but also help for marshalling and shunting work in station yard.

Stock Rail They are the main rails of the track to which the tongue rails fit closely against them.

Tongue Rail Lie between the two stock rails and are tapered to a point or tongue. Supported on sliding plates and connected by stretcher bars near the toe and both the tongue rails moves same distance or gap.

Heel Block Inserted between the heel of tongue rail and stock rail used to provide clear gap for the wheel flange.

Stretcher Bar Toes of both tongue rails are connected by a bar, so that each moves through the same distance while changing the points.

Necessity In case of roads, the facilities for turning of vehicles from one path to another, do not require any special arrangement as the wheels have no flanges.

Necessity The direction of movement of vehicles is controlled by the driver and the steers according his own will.

Necessity But this is not true in case of railways because the wheels are provide with flanges inside, so the direction of movement and the direction of vehicles to another track are controlled automatically by the wheel flanges rather than the driver as in case of roads.

Necessity The problem of diversion of trains from one track to another is solved by special arrangements known as points and crossings.

Important Terms Facing Direction: if someone stands at toe of switch and looks towards the crossing, then the direction is called “facing direction.”

Important Terms Trailing Direction: if someone stands at the crossing and looks towards the switches, then the direction is called “Trailing direction.”

Important Terms Facing Points of turnouts are those where trains pass over the switches first and then they pass over the crossings. These are important to specify when the direction of movement of trains reserved for facing direction.

Important Terms Trailing Points of turnouts are those on the opposite side of facing points in which trains pass over the points first and then they pass over the switches. These are important to specify when the direction of movement of trains reserved for trailing direction.

TRAILING DIRECTION FACING DIRECTION

Important Terms Right-hand Turnout: if a train from main track is diverted to the right of the main route in the facing direction then this diversion is known as Right-hand turnout.

Important Terms Left-hand Turnout: if a train from main track is diverted to the left of the main route in the facing direction then this diversion is known as Left-hand turnout.

Marshalling Yard

Marshalling Yard Marshalling yard is said to be a “Machine to receive, break-up, re-form and despatch trains onwards”. In other words, a marshalling yard is one where trains and other loads are received, sorted out and new trains formed, and despatched onward to their destination.

Marshalling Yard The marshalling yard are provided at important junction stations which act as distributing centre for various destinations.

Marshalling Yard In marshalling yard, loaded and empty goods wagons are first received from different lines for booking in different directions and then the wagons are separated, sorted and despatched onward in full trains for each train.

Marshalling Yard While making full trains, the wagons are arranged in order of the stations to enable convenient detaching of wagons at wayside stations.

Marshalling Yard The important functions of a Marshalling Yard are: Reception Sorting Departure

Marshalling Yard Sidings for each function or combination of two or combination of all three functions are provided. When a branch line from main line or a loop line terminates at a dead end with a buffer stop or sand hump, it is called a ‘siding’.

Marshalling Yard Thus various sidings – (a) Reception siding, (b) Sorting siding and © departure siding – are provided in the marshalling yard.

Marshalling Yard Seprarate set of sidings are provided for marshalling of wagons in up and down directions.

Types: Marshalling Yard Marshalling yards are classified into three types: Flat yards Gravitational Yards Hump Yards

Types: Marshalling Yard A marshalling yard can be constructed of any of the above types depending upon the ground contours.

Flat Yards In this type of yard, the entire space of the yard is almost level and all the sorting works or movement of wagons are carried out by means of engines running to and fro.

Flat Yards This arrangement is costly due to more consumption of power in the use of engines.

Flat Yards But this type of yard is justified where the available space is limited for the layout of marshalling yard. The other two types of yards require more area for their layouts.

Gravitational Yards In this type of yard, the tracks are laid at such a gradient, that wagons can move of their own under the action of gravity.

Gravitational Yards Movements of wagons are controlled by wagon brakes manually.

Gravitational Yards Thus, movements of wagons are carried out by the action of gravity accompanied by the engine power.

Gravitational Yards The success of such gravitational yards requires certain slope for the formation.

Gravitational Yards But the topography of the yard site may not permit for such a formation.

Hump Yards In this type of yard, humps or summits or artificial hills are provided and wagons are pushed upon a hump by the engine. Switches are aligned to route the car into the proper track as it rolls down the other side.

Hump Yards Hump level Pushing end (Initial Stage) 1:50 or 1:175 1:50 or 1:150 1:300 Movement of wagons under gravity

Hump Yards Reception Siding Departure Siding Cabin Sorting Siding Hump

Hump Yards The hump is located at the entrance to the sidings.

Hump Yards The wagons are then allowed to move into the sidings down the hump under the action of gravity.

Hump Yards Therefore, a hump yard can be said to be a gravitational yard as shunting operations are done more quickly than flat or gravitational yards.

Hump Yards The hump yards are also economical as no power is required to move the wagons.

Hump Yards However, hump yards are little uncertain in their action, as the rate of movement of wagons depends on: (i) weather conditions; (ii) different type of axle boxes; (iii) weight of the wagons.

Hump Yards The individual wagons or group of wagons are pushed up the hump and from there, they roll down to appropriate sidings.

Hump Yards The stopping of wagons rolling down in hump yards at the exact place is carried out by following methods: Manual method Automatic method Skid method

Dowty retarder An hydraulic device that regulates the speed of rail cars as they roll down an inclined track. The devices are built for a specified speed, set at the factory. If the rail car is below the set speed, the device offers no resistance. If the car speed is at or greater than the speed setting, an internal valve is activated to provide a resistance to the wheel, thus slowing the car. This keeps cars rolling within a relatively narrow range of speeds