Railway Terminologies

8/14/2019 Railway Terminologies

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ORESEGUN ADEDAPO TOLULOPEF/HD/06/3510041

SLEEPER

A railroad tie, cross tie, or railway sleeper is a rectangular

object used as a base for railroad tracks. Sleepers are members

generally laid transverse to the rails, on which the rails are

supported and fixed, to transfer the loads from rails to the ballast

and sub grade below, and to hold the rails to the correct gauge.

Traditionally, ties have been made ofwood, but concrete is now

widely used, Steel ties and plastic composite ties are currently

used as well, however far less than wood or concrete ties. As of

January 2008, the approximate market share, in North America,

for traditional wood ties was 91.5%, whereas the approximate

combined market share for (all) concrete, steel, azobe (exotic

hardwood) and plastic composite ties was 8.5%. (source: A & K

Railroad Material co.)

Ties are normally laid on top oftrack ballast, which supports and

holds them in place, and provides drainage and flexibility. Heavy

crushed stone is the normal material for the ballast, but on lines

with lower speeds and weight, sand, gravel, and even ash from

the fires of coal-fired steam locomotives have been used.

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Wooden Sleeper

Timber ties are usually of a variety ofhardwoods, oak being a

particularly popular material. Some lines use softwoods,

sometimes due to material necessity; while they have the

advantage of accepting treatment more readily, they are more

susceptible to wear. They are often heavily creosoted or, less

often, treated with other preservatives, although some timbers

(such as sal) are durable enough that they can be used untreated.

The main problem with wood is its tendency to rot, particularly

near the points where they are fastened to the rails. The timber

industry has responded to decreased use of timber by promoting

its advantages; wooden ties still dominate the North American

market.

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Concrete Sleeper

Concrete ties have become more common mainly due to greater

economy and better support of the rails under heavy traffic. In the

early period railway history, wood was the only material used for

making ties in Europe. Even in those days, occasional shortages

and increasing cost of wood posed problems. This induced

engineers to seek alternatives to wooden ties. As concrete

technology developed in the 19th century, concrete established

its place as a versatile building material and could be adapted to

meet the requirements of railway industry.

In 1877, Mr. Monnier, a French gardener and inventor of reinforced

concrete, suggested that cement concrete could be used for

making ties for railway track. Monnier designed a tie and obtained

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a patent for it, but it was not successful. Designs were further

developed and the railways ofAustria and Italy produced the first

concrete ties around the turn of the 20th century. This was closely

followed by other European railways.

Major progress could not be achieved until World War II, when the

timbers used for ties was extremely scarce due to material

shortages. Due to research carried out on French and other

European railways, the modern concrete tie was developed.

Heavier rail sections and long welded rails were also being

produced, requiring higher quality ties. These conditions spurred

the development of concrete ties in France, Germany and Britain,

where the technology was perfected.

Toward the end of the 1990s, the Long Island Rail Road, followed

by Amtrak, began rehabilitation of their lines in the New York

metropolitan area by installing steel-reinforced concrete ties,

updating some of the busiest rail lines in North America .

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Steel Sleeper

Steel ties, which are relatively light in weight, are sometimes used

for sidings and temporary tracks. They have the advantages of

being relatively free from decay and attack from insects, as well

as providing excellent gauge restraint, but are prone to rust and

wear at the rail seat; they also require frequent replacement and

tightening of fastenings. They are generally unsuited to railway

lines carrying vehicles traveling at over 60 mph (100 km/h)

because they provide no damping, all force being transmitted to

the underlying track ballast. Prefabricated, all-metal "Jubilee"

track, which was developed in the late nineteenth century for use

in quarries and the like and saw some use in major civil

engineering projects, is one example of steel ties in use.

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Standard gauge

The standard gauge of 1,435 mm (4 ft 8 in) was chosen for the

first main-line railway, the Liverpool and Manchester Railway

(L&MR), by the British engineer George Stephenson; however, the

de facto standard for the colliery railways where Stephenson had

worked was 4 ft 8 in. Whatever the origin of the gauge it seemed

to be a satisfactory choice: not too narrow and not too wide.

Brunel on the Great Western Railway chose the broader gauge of

2,140 mm (7 ft 0 in) partly because it offered greater stability

and capacity at high speed, but also because the Stephenson

gauge was not scientifically selected. The Eastern Counties

Railway chose five-foot gauge, but soon realized that lack of

compatibility was a mistake and changed to Stephenson's gauge.

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The conflict between Brunel and Stephenson is often referred to

as the Gauge War.

In 1845 a United Kingdom of Great Britain and IrelandRoyal

Commission recommended adoption of 1,435 mm (4 ft 8 in) as

standard gauge in Great Britain; and in Ireland a standard gauge

of 5 ft 3 in (1,600 mm). The following year the Parliament of the

United Kingdom passed the Gauge Act, which required that new

railways use the standard gauge. Except for the Great Western

Railway's broad gauge, few main-line railways in Great Britain

used a different gauge. The last Great Western line was finally

converted to standard gauge in 1892.

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TRACK BALLAST

Track ballast forms the track bed upon which railroad ties (US)

or railway sleepers (UK) are laid. It is packed between, below, and

around the ties. It is used to facilitate drainage of water, to

distribute the load from the railroad ties, and also to keep down

vegetation that might interfere with the track structure. This also

serves to hold the track in place as the trains roll by. It is typically

made ofcrushed stone, although ballast has sometimes consisted

of other, less suitable materials. The term "ballast" comes from a

marine shipping term for the stones used to weigh down a ship.

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M aterial properties

A good ballast should be strong, hard-wearing, stable, drainable,

easy to clean, workable, resistant to deformation, easily available,

and reasonably cheap to purchase. Early railway engineers did

not understand the importance of quality track ballast; they would

use cheap and easily-available materials such as ashes, chalk,

clay, earth, and even cinders from locomotive fireboxes. It was

soon clear that good-quality ballast made ofrock was necessary if

there was to be a good foundation and adequate drainage.

Good quality track ballast is made of crushed natural rock with

particles between 28mm and 50mm in diameter; a high

proportion of particles finer than this will reduce its drainage

properties, and a high proportion of larger particles result in the

load on the ties being distributed improperly. Angular stones are

preferable to naturally rounded ones, as these interlock with each

other, inhibiting track movement. Soft materials such as9
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limestone are not particularly suitable, as they tend to degrade

under load when wet, causing deterioration of the line; granite,

although expensive, is one of the best materials in this regard.

In the early days of railroads in the United States, much material

for ballast came from rock found in the local area. In the Midwest,

for example, much use was made ofquartzite, while states in the

southeast, such as Florida, made use oflimestone. One specific

type of quartzite used in the Midwest earned the name "Pink

Lady" due to its color; in other areas, the ballast can be a mix of

light and dark colors called "Salt and Pepper".

Construction

The thickness of a layer of track ballast depends on the size and

spacing of the ties, the amount of traffic expected on the line, and

various other factors. Track ballast should never be laid down less

than 150 mm (6 inches) thick; high-speed railway lines may

require ballast up to half a metre (20 inches) thick. An insufficient

depth of ballast overloads the underlying soil; in the worst cases,

this can cause the track to sink. If the ballast is less than 300 mm

(12 inches) thick, this can lead to vibrations, which can damage

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nearby structures (though increasing the depth beyond this has

no measurable effect).

Track ballast typically sits on a layer of sub-ballast; the latter is

typically made of small crushed stones. It gives a solid support for

the top ballast, and seals out water from the underlying ground.

Sometimes, an elastic mat is placed under the ballast layer as

well; this can allow for significant reductions in vibration.

It is essential for ballast to be piled as high as the ties, and for a

substantial "shoulder" to be placed at their ends; the latter being

especially important, since this ballast shoulder is, for the most

part, the only thing restraining lateral movement of the track. The

ballast shoulder should be at least 150 mm (6 inches) wide under

any circumstances, and may be as large as 450 mm (18 inches).

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Maintenance

If ballast is badly fouled, the clogging will reduce its ability to

drain properly; this, in turn, causes more debris to be sucked up

from the sub-ballast, causing more fouling. Therefore, keeping the

ballast clean is essential.

It is not always necessary to replace the ballast if it is fouled, nor

must all the ballast be removed if it is to be cleaned. Removing

and cleaning the ballast from the shoulder is often sufficient, if

shoulder ballast is removed to the correct depth. While this job

was historically done by manual labour, this process is now, like

many other railway maintenance tasks, a mechanised one, with a

chain of specially-designed railroad cars handling the task. One

wagon cuts the ballast and passes it via a conveyor belt to a

cleaning machine, then the cleaning wagon washes the ballast,

and deposits the dirt and ballast into other wagons for re-use or

disposal, respectively. Such machines can clean up to two

kilometres of ballast in an hour.Cleaning, however, can only be done a certain number of times

before the ballast is damaged to the point that it cannot be re-

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used; furthermore, track ballast that is completely fouled cannot

be corrected by shoulder cleaning. In such cases, it is necessary

to replace the ballast altogether. One method of "replacing"

ballast, if necessity demands, is to simply dump fresh ballast on

the track, jack the whole track on top of it, and then tamp it

down; alternatively, the ballast underneath the track can be

removed with an undercutter, which does not require removing or

lifting the track.

Regular inspection of the ballast shoulder is important; as noted

earlier, the lateral stability of the track depends upon the

shoulder. The shoulder acquires some amount of stability over

time, being compacted by traffic; maintenance tasks such as

replacing ties, tamping, and ballast cleaning can upset this

stability. After performing these tasks, it is necessary for either

trains to run at reduced speed on the repaired routes, or to

employ machinery to compact the shoulder again.

If the trackbed becomes uneven, it is necessary to pack ballast

underneath sunk ties to level the track out again. This is, in the

mechanized age, usually done by a ballast tamping machine. A

more recent, and probably better, technique is to lift the rails and13
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ties, and to force stones, smaller than the track ballast particles

and all of the same size, into the void. This has the advantage of

not disturbing the well-compacted ballast on the trackbed, as

tamping is likely to do. This technique is called pneumatic ballast

injection (PBI; or, less formally, "stoneblowing"). However, this

technique is not as effective with fresh ballast, as the smaller

stones tend to move down between the larger pieces of ballast.

RAILROAD SWITCH

A railroad switch, turnout or [set of]points are a mechanical

installation enabling railway trains to be guided from one track to

another at a railway junction

The switch consists of the pair of linked tapering rails, known as

points (switch rails orpoint blades), lying between the diverging

outer rails (the stock rails). These points can be moved laterally

into one of two positions so as to determine whether a train

coming from the narrow end will be led towards the straight path

or towards the diverging path. A train moving from the narrow

end towards the point blades is said to be executing a facing-

point movement.

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Unless the switch is locked, a train coming from either of the

converging directs will pass through the points onto the narrow

end, regardless of the position of the points, as the vehicle's

wheels will force the points to move. Passage through a switch in

this direction is known as a trailing-point movement.

A switch generally has a straight "through" track (such as the

main-line) and a diverging route. The handedness of the

installation is described by the side that the diverging track

leaves. Right-hand switches have a diverging path to the right of

the straight track, when coming from the narrow end and a left-

handed switch has the diverging track leaving to the opposite

side.

A straight track is not always present; for example, both tracks

may curve, one to the left and one to the right or both tracks may

curve, with differing radii, in the same direction.

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Frog (common crossing)

The frog (common crossing) refers to the crossing point of two

rails. This can be assembled out of several appropriately cut and

bent pieces of rail or can be a single casting. A frog forms part of

a railroad switch, and is also used in a level junction (flat

crossing). The frog is a point of weakness because the wheels are

unsupported for a short distance and can inflict wear and

damage. There is also a small risk that the wheels may go the

wrong way.

On lines with heavy and/or high-speed traffic, a swingnose

crossing is often used. As the name implies, there is a second set

of points located at the frog. This effectively eliminates the gap in

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the rail that normally occurs at the frog, so long as trains are

moving in the direction to which the switch is aligned. Two switch

machines are required to make a movable point frog switch work.

This use of the word "frog" derives from the appearance of the

triangular assemblage of rails which recalls the frog of a horse's

hoof.

How To Determine The Number of a Frog

The frog number is the ratio of its length (measured on center

line of frog) to its width, or the number of inches in length

necessary for it to spread one inch in width. For example, a No. 3

frog spreads 1 in 3, a No. 5 spreads 1 in 5, a No. 8 spreads 1 in 8,

etc.

To determine the number of a straight frog, measure across the

frog point at place (A) where the distance between the gauge

lines is an even number of inches: measure again where the

distance (B) is an inch greater than at (A); the number of inches

(C) between the two measured sections (A and B) is the number

of the frog as shown below.

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Guard rail (check rail)

A guard rail (check rail) is a short piece of rail placed alongside

the main (stock) rail opposite the frog. Guard Rail protects the

frog point by preventing derailments and increasing the speed

that traffic can move safely. These exist to ensure that the wheels

follow the appropriate flangeway through the frog and that the

train does not derail. Generally, there are two of these for each

frog, one by each outer rail. Guard rails are not required with a

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"self-guarding cast manganese" frog, as the raised part of the

casting serve the same purpose. These frogs are for low-speed

use and are common in rail yards.

TIE PLATE

A tie plate (US) or baseplate (UK) in railroading is a steel plate

used between flanged T rail and the crossties. The tie plate

increases bearing area and holds the rail to correct gauge. They

are fastened to wooden ties by means ofspikes or bolts through

holes in the plate.

The part of the plate under the rail base is tapered, setting the

cant of the rail, an inward rotation from the vertical. The usual

slope is one in forty (1.4 degrees). The top surface of the plate

has one or two shoulders that fit against the edges of the base of

the rail. The double-shoulder type is currently used. Older single-

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shoulder types were adaptable for various rail widths, with the

single shoulder positioned on the outside (field side) of the rails.

Most plates are slightly wider on the field side, without which the

plates tend to cut more into the outsides of the tie, reducing cant

angle.

Tie plates came into use around the year 1900, before which time

flanged T rail was spiked directly to the ties.

WELDED RAILS

In this form of track, the rails are welded together by utilizing

flash butt welding to form one continuous rail that may be several

kilometres long, or termite welding to repair or splice together

existing welded rail segments. Because there are few joints, this

form of track is very strong, gives a smooth ride, and needs less

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maintenance. The first welded track was used in Germany in 1924

and the US in 1930 and has become common on main lines since

the 1950s.

Flash butt welding is the preferred process which involves an

automated track laying machine running a strong electrical

current through the touching ends of two unjoined pieces of rail.

The ends become white hot due to electrical resistance and are

then pressed together forming a strong weld. Thermite welding is

a manual process requiring a reaction crucible and form to

contain the molten iron. Thermite-bonded joints are also seen as

less reliable and more prone to fracture or break.

Because of the increased strength of welded track, trains can

travel on it at higher speeds and with less friction. Welded rails

are more expensive to lay than jointed tracks, but have much

lower maintenance costs.

Rails expand in hot weather and shrink in cold weather. Because

welded track has very few expansion joints, if no special

measures are taken it could become distorted in hot weather and

cause a derailment (a condition known in North America as sun

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kink, and in Britain as buckling). In North America a rail broken

due to cold-related contraction is known as apull-apart.

To avoid this, welded rails are laid on concrete or steel sleepers,

which are so heavy they hold the rails firmly in place. Great

attention is paid to compacting the ballast effectively, particularly

the shoulder over the ends of the sleepers, to prevent them from

moving. Even so, in extreme weather, foot patrols monitor

sections of track known to be problematic.

RAIL ANCHORS

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Rail Anchors are designed to eliminate creepage of track by

providing a large bearing surface against the rail base and tie.

The anchors prolong the life of wood ties by preventing cutting

and wear.

JOINTS

These are points where steel rail tracks are joined in order to

achieve to goal of making the track continuous.

Because each joint is a relatively weak spot in a track, design

engineers have reduced the number of joints by lengthening the

rails. The customary length when locomotives were introduced

was 0.9 m (3 ft), but in the 1830s this was increased to 4.6 or 6.1

m (15 or 20 ft). Early in the 20th century the most common length

for rails was 9.1 m (30 ft), and this figure soon became 10 m (33

ft) when 12.2-m (40-ft) freight cars came into general use. To

some extent the length of rails has been limited by difficulties in

transporting them. Rails 18.3 m (60 ft) long, used on one British

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railroad as early as 1894, were installed on some United States

railroads, others of which have 13.7-m (45-ft) rails.

In the United States rails are often butt-welded together to form

lengths as long as 0.4 km (0.25 mi). At first this was done

cautiously for fear that expansion and contraction due to

temperature changes would cause buckling in great lengths of

continuous rail. Experience showed, however, that longitudinal

expansion and contraction are not excessive and need not lead to

buckling. Techniques were developed for making butt welds as

strong as the rails themselves. Where welding is not used, rails

are joined by bars bolted to the sides so as to cover the joint.

Stevens is credited with inventing the first such joint. On earlier

railroads using metal rails, the individual sections were not

fastened together in any way.

Advances in track construction in the 20th century included using

longer and stronger joint bars and wider tie plates to spread the

weight of trains more evenly on the ties. Tie plates with shoulders

to brace the rail on either side are used, and nearly all U.S.

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railroads have special braces called anticreepers, designed to

prevent longitudinal displacement.

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