Marshalling Yards:
Introduction and Definition:
A Yard can be defined by the functions it performs. It is the place or the activity center on a Railway system, where the trains or rolling stock or group of rolling stocks are received, reformed into trains or loads after marshaling and are despatched to their destinations. A Yard is, thus, a classifying and distributing machine with facilities for receiving, sorting and dispatching the wagons to their various destinations, after the prescribed attention.
This necessarily involves detention of trains and wagons, but it is inherent in railway working to have Marshalling Yards.A Yard is a specified area laid out with a network of tracks divided into several grids for receiving sorting, forming and dispatching of trains.
Necessity and Significance of Marshalling Yards:
Though Yards perform very important functions, yet the work done in a Marshalling Yard is only indirectly productive. Yards are the operational necessity and are even considered as necessary evils. The ingenuity of the operating man consists in putting in the minimum number of the wagons into the minimum possible number of Marshalling Yards by forming trains for the farthest common points subject to rules and regulations.
If the control is analogous to the brain of the operating system, a large Marshalling Yard is akin to the heart and its working to be planned and monitored with considerable care. Constant vigilance and intelligent and efficient work in day-to-day functions are required as it is one of the important factors governing the capacity and the output of a section.
A Marshalling Yard affects not only the traffic it deals with, but also the entire train running on the section, in particular, and the working of the Railway system in general. The Yard gets easily congested if treated as a holding Yard and if more trains are put in than taken out.
Classification of Yards:
Yards can be classified as:
- Terminal Yard
- Marshalling Yard.
Terminal Yard:
Terminal Yard means the Yard attached to terminal goods sheds where a large number of wagons are loaded and/or unloaded. This term is also used for every goods Yard, where a goods train terminates.
Marshalling Yard:
Yards are nominated as Marshalling Yards on the basis of the work done and wagons dealt with. The Yard which receives and despatch trains without any shunting on them are classified
Transit Yard:
In such Yard generally change of Crew, Engine or C&W examination etc. only take place in addition to formations of a few loads. During the last 50 years, such yards have become anachronistic and have given way to modern freight terminals the world over.
Objectives of Marshalling Yards:
- Accepting trains without detention at an adjacent station outside the Yard.
- Minimising the detention of wagons in the Yard.
- Timely supply and placement/removal of wagons to the goods shed, transshipment shed, repacking shed, sidings, carriage, and wagons depots etc. served by the Yards.
- Forming block loads for the farthest destination.
- Ensuring convenient Marshalling of wagons from the operational efficiency point of view.
- Ensuring right time start for outgoing trains.
Economy:
- Maximising productivity of resources and minimising the detention to Train Engine/Light Engine, Shunting Engine, crew and other connected staff.
- Optimising the Trailing load of the trains.
- Optimising shunting engine utility.
Safety:
- Ensuring minimum damage to wagons and consignments loaded on the wagons during the shunting operations.
- Ensuring safe Marshalling and C&W pattern of examination.
- Elimination of Yard accidents.
Kinds of Yards:
Marshalling Yard can be classified into three groups on the basis of the method of sorting out trains:
Flat Yard:
Flat Yards are generally laid on flat or level land where shunting operations are carried out with the help of engine by push and pull method. Such Yard is economical in space but slow in working and wasteful in shunting engine hours.
Hump Yard:
Hump Yards are constructed by providing gradients between reception and the sorting and despatch lines and the grids. The gradients are created by constructing an artificial hump suitable for the purpose. The gradient of the hump is constructed in such a manner that the wagons roll down of their own to specified sorting lines from the summit(apex) of the hump after having been pushed up by the shunting engine.
The load is pushed up by engine towards the hump from one side of the hump so that the uncoupled portion of the load rolls away towards another side of the hump in sorting/despatch line. There are generally two humps one for ‘Down’ and one for ‘Up’ Yard. These Yards are economical in shunting engine hours as compared to flat Yards.
Gravity Yard:
Gravity Yards are constructed where the natural contour of land permits a suitable falling gradient stretched over a sufficient length. The falling gradient makes it possible to use the Yard to the fullest extent in Marshalling wagons/trains thus minimizing the use of engine power. Therefore gravity Yards are more economical than flat Yards but the layout of it dependent on the availability of plenty of land with the required topography which is seldom possible.
Some Terms Concerning Marshalling Yards and its Components:
Reception Yard:
Reception Yard comprises of the lines on which the incoming trains are received and stand clear of other running lines while waiting their turn to be dealt with. Incoming trains may be composed of wagons which are to go through after changing of power, Crew, and Guard or of wagons requiring sorting and Marshalling. Separate grids may be provided in the reception Yard one for through trains and another for terminating trains. Separate reception Yards may be provided for trains coming from different directions. The grids for through trains bye pass the hump.
Sorting Yards:
It is a Yard in which the trains are broken up on the different sorting lines for various directions or specified destinations, as per Marshalling order so as to form them into trains and prepare them for correct Marshalling.
Marshalling Lines:
The lines in which sorted wagons are separated first, if necessary, according to commodity, type of vehicle, Marshalling order, direction and secondly reformed into trains in special order to meet the requirements of the section ahead or any other special transportation requirement.
Departure Yard:
In which load can be held ready for departing trains. Separate departure Yards for trains for different directions are provided in large Marshalling Yard.
Shunting Neck:
It is a line in a Yard leading to sorting lines on which the actual shunting of the trains maybe done clear of any running lines.
Gathering lines:
It is a line on which the turnouts to other lines are arranged.
Transfer lines:
These lines are meant for transferring wagons, generally from up Yard to down Yard or vice versa, in case of two separate Marshalling or hump Yards.
Bypass or avoiding lines:
It is a line, which skirts the hump, and its object is to avoid engine going over the hump. It joins the shunting neck at one end and the main hump line short of the king point at the other. It is also used for vehicles, which cannot be passed over the hump into the sorting Yard due to various reasons.
Engine Run Round Line:
It is the line reserved for movements of incoming and outgoing train engines to and from the Yard or the loco shed, or for independent movement of shunting engines.
Engine Escape Line:
It is the line meant for engine movements to and from the loco shed from and to Yard so that engine returning to loco sheds do not interfere with engines, going out of the loco shed, or with any other movements in the Yard.
King Points:
The first pair of points a wagon meets with after passing over the hump are called ‘King Points’. They divide the sorting Yard into two portions
Queen Points:
The second pair of points a wagon meets with on its way downwards are called Queen Points, which further divide the sorting Yards into four portions.
Jack Points:
The third pair of points a wagon meets are called the jack points and these serve to divert the rolling wagons into the different grids of the sorting Yard. Points beyond jack points called ‘Ten points’.
Note: In a hump Yard there is usually a pair of ‘king points’ two pairs of ‘Queen points’ and four pairs of ‘Jack points’.
Retarders:
One of the main problems in the working of a hump Yard is to adjust suitably the speed of the humped wagons rolling down so that they may not cause damage by humping down against wagons already standing on the same line. The speed of the humped wagons varies according to the force of the push given by the engine, the height of the hump, the weight the nature of the axle box (viz. roller bearing or plain bearing) as also on the weather prevailing.
In mechanized Yards, retarders or rail brakes are installed to reduce and keep the speed of the humped vehicles under control. The retarders may be automatic or manually operated.
Skids:
At Yards, where mechanical retarders are not provided skids are placed on the sorting lines to control the speed of the humped wagons. These skids are placed by skid porters and the skids automatically come out of runways, where provided, or/and are removed after the wagon has come to stop.
Brake van siding: In this siding, brake vans of incoming terminating trains etc. may be detached for subsequent attachment to originating trains.
Special stock siding:
These are provided for keeping with special type stock, cattle wagons containing commodities like explosives which cannot be humped.
Stabling Lines:
In large Yard, ballast, material or POH special, empty military special trains are sometimes required to be stable. Moreover, there are heavy accumulations of certain classes of stock for various reasons. The stabling accommodation in the Yard should, therefore, be ample so that the Yard may retain its mobility in spite of any accumulation of wagons or other setbacks.
Sick lines:
Normally sick wagons are sorted out in the sorting Yard, then sent in the sick line. As the time taken in placing wagons into and withdrawing them from a sick line is usually several times the time spent on actual repairs. Provisions should be made to carry out whatever repairs are possible in the sorting Yard itself by providing sick lines.