LWR Basics

8/11/2019 LWR Basics

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LONG WELDEDRAILS


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LWR (GENERAL) FISHPLATED TRACK-Maintenance problem and poor

riding comfort DREAM OF RAILWAY ENGINEERS- Joint less Track TWO WAYS OF ACHIEVING

ROLLING OF LONGER RAILS Logistic problem in transporting, loading, unloading

Length of cooling boxes WELDING

PRESENT STATUS OF ROLLING OF RAILS ININDIA

13 m 26 m 65 m

PLANNING -UP TO 480 M


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DEVELOPMENT OF LONG WELDED

RAILS COMMERCIAL WELDING 1932/ 1905 DURING THIRTIES

STANDARD RAIL Length 5.5 m TO 27 m

Weight 22 kg TO 65 kg WELDED RAILS

18 m TO 380 m

LONGER RAILS USED BUT NOT SURE OF GAP BTC STUDY REVEALED (British Transport Commission)

GAP INDEPENDENT OF LENGTH OF RAILS


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DEVELOPMENT OF LONG WELDED

RAILS (Contd) OTHER MAJOR WORRY

ABILITY TO WITHSTAND THERMAL FORCES RESISTANCE TO BUCKLING

STIFFNESS OF RAIL RAIL SLEEPER FASTENINGS BALLAST RESISTANCE

LWR accepted after gaining confidence about

resistance to buckling


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DEVELOPMENT OF RAIL WELDING IN

INDIA IN NINETEEN THIRTIES

GIP undertaken welding using electrical process BN railways started conducting trials

IN NINETEEN FOURTIES

NW, GIP, & EI Railways commenced trials with weldedrails

FROM 1947 TO 1966 WELDED PANELS WERE

USED TO REDUCE MAINTAINCE PROBLEM 3 RAIL PANELS 5 RAIL PANELS 10 RAIL PANELS


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DEVELOPMENT OF RAIL WELDING IN

INDIA BUT LARGE SCALE MAINTAINACE

PROBLEMS Increased rail battering and hogging Bent fish plates


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DEVELOPMENT OF RAILWELDING IN INDIA

COMMITTEE NOMINATED BY BOARDRECOMMENDEDi)3 Rail panels are maximum with fish-plated joints

ii)Discontinue further 5/10 rail paneliii)Cut into 2.5 rail panelsiv)RDSO to conduct further studies for deciding thetrack structure, temp., Ballast condition for layingLWR


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BASIC DEFENITIONS1.1 LONG WELDED RAILS (LWR) is a welded rail, thecentral part of which does not undergo any longitudinalmovement due to temp. variations. A length greater than250m on B.G and 500m on M.G will normally functionas LWR.The maximum length of LWR under Indian conditions

.

1.2 CONTINUOUS WELDED RAILS (CWR) is a LWR, whichwould continue through station yards including points

and crossings.

1.3 SHORT WELDED RAILS (SWR) is a welded rail whichcontracts and expands throughout its length.


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BASIC DEFENITIONS(Contd.)

1.4 BREATHING LENGTH is that length at each end ofLWR/CWR which is subjected to expansion/

contraction on account of temp. variations.1.5 SWITCH EXPANSION JOINT (SEJ) is an expansion

joint installed at each end of LWR/CWR to permit

expans on con rac on o e a o n ng rea nglengths due to temp. variations.1.6 BUFFER RAILS are a set of rails provided in lieu of

SEJ at the ends of LWR/CWR to allowexpansion/contraction of the adjoining breathinglengths due to temp. variations.


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BASIC DEFENITIONS1.7 DESTRESSING is the operation undertaken with or

without rail tensor to secure stress-free conditions in

the LWR/CWR at the desired/specified rail temp.

1.8 RAIL TEMP . is the temp. of the rail at site as

recor e y an approve type o ra t ermometer.

1.9 MEAN RAIL TEMP. (tm)for a section, is the avg. of

the max. & min. rail temps. recorded for the section.

1.10 INSTALLATION TEMP. (ti) is the average rail temp.during the process of fastening the rails to thesleepers at the time of installation of the LWR/CWR.


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Destressing Temp.The rail can be fixed to the sleepers by fastenings afterdestressing, at a temp. anywhere within the range betweenmaximum and minimum rail temp.

It is prudent to fix the destressing temp. higher than themean rail temp.

Since the operation of fastening the rails to the sleepersafter destressing takes time during which rail temp. canvary, a range has been recommended for t d instead of afinite value.


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BASIC DEFENITIONS1.11 DESTRESSING TEMP. (t d) is the avg. rail temp.during the period of fastening the rails to the sleepersafter destressing LWR without the use of rail tensor.

If rail tensor is used, t d for all practical purposes isequal to t o as defined below.Range of t d or t o shall be:

Rail Section Range52 kg & heavier t m+5 oC to t m+10 oCOthers t m to t m + 5 oC

1.12 PREVAILING RAIL TEMP (tp)

is the rail temp. prevailingat the time when any operation connected with destressing iscarried out.

1.13 STRESS-FREE TEMP (t o) is the rail temp. at which the rail

is free of thermal stress.


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Stress-free Temp.This is the rail temp. at which the rail is free ofthermal stresses. For all practical purposes, this isequivalent to destressing temp.

wo essent a erences:i) Stress-free temp. is applicable for any

destressing operation wherein rail tensors areused.

ii) Stress-free temp. is a finite value.


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BASIC DEFENITIONS(Contd )1.14 RAIL TENSOR is a hydraulic or mechanical device

used for stretching the rail physically .1.15 ANCHOR LENGTH (l a) is the length of track required

to resist the pull exerted on rails by the rail tensor attem . t .For practical purposes, this may be taken as equal to2.5m per degree celsius of (t o-tp) for BG.

1.16 HOT WEATHER PATROL is the patrol carried out

when the rail temp. exceeds t d+20 oC.1.17 COLD WEATHER PATROL is the patrol carried out

during cold months of the year in specified sections as

per instructions of Chief Engineer.


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BASIC DEFENITIONS(Contd)

CONSOLIDATION OF TRACK FOR OTHER THAN CONCRETE SLEEPERS

WHEN BALLAST COMPACTION DONE WITH HANDOPERATED COMPACTORS

BG 3,00,000 GROSS TONNES MG 1,00,000 GROSS TONNES

MECHANISED SHOULDER AND CRIB COMPACTOR BG 50,000 GROSS TONNES MG 20,000 GROSS TONNESOR MINIMUM OF TWO DAYS WHICHEVWR IS LATER


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BASIC DEFENITIONS(Contd) CONCRETE SLEEPERS

BG 50,000 GROSS TONNES MG 20,000 GROSS TONNES

OR MINIMUM OF TWO DAYS WHICHEVWR IS LATER

DTS

FOR NEWLY LAID LWR/CWR, AT LEAST 3ROUNDS OF PACKING ( LAST TWO WITH ONTRACK TAMPER )


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BASIC PRINCIPLES (Contd) RAIL IS RESTRAINED DUE TOi) Creep resistance on account of friction

between the rail and the sleeper at the railseatii Cree resistance further offered b the rail-

sleeper fasteningThis results into less expansion/ contraction

IN LWR RAIL SLEEPER FRAME AS AWHOLE TENDS TO MOVES (DUE TOTOE LOAD )


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BASIC PRINCIPLES (Contd)

RAIL/SLEEPER FRAME IS RESRTAINED BYBALLAST RESISTANCE

Assumed constant Build up progressively from end of LWR

Temperature variation Rail section

IMPORTANCE OF MEASUREMENT OF RAILTEMPERATURE Forces in rail to be kept in limit Maintenance operations


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THERMAL FORCESTHERMAL FORCES IN THE CENTRAL

PORTION:P = EA tWhere,P = thermal force in the rail (kg)

= mo u us o e as c y o ra s ee . xkg/sq.Cm) = co-efficient of linear expansion of steel

(1.152 x 10-5

/ o

c)A = area of x-section of the rail (sq.cm)t = variation of rail temp. from t d / t o (oc)


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PERMITTED LOCATIONS1. GENERAL CONSIDERATIONS:

1.1 AS A RULE, CTR(P) SHALL PROVIDE FOR LWR/CWR.ALSO, EXISTING RAILS ON PERMITTED LOCATIONSMAY BE CONVERTED.

1.2 NEW CONSTRUCTIONS / DOUBLINGS / GAUGECONVERSIONS / REVISED ALIGNMENT / PERMANENTDIVERSIONS SHALL BE OPENED WITH LWR/CWR.

1.3 IN GOODS RUNNING LINES, GOODS YARDS,RECEPTION YARDS & CLASSIFICATION YARDS, RAILJOINTS MAY BE WELDED TO FORM LWR.


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PERMITTED LOCATIONS (Contd)

2.2 ALIGNMENT:2.1 Shall not be laid on curves sharper than 440m

radius both for BG & MG. In temp. Zone I up to 5 o on BG

52 k rail on PSC m + 7 with followinprecautions

Increase shoulder ballast to 600 mm on outsideand provide for 100 m beyond the tangent point

Reference marks every 50 m for creep SEJ 100 m away from tangent point


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PERMITTED LOCATIONS(Contd)

Each curve greater than 250 m length provideSEJ on either side.

May be continued through reverse curves

not sharper than 875m radius. For reverse curves sharper than 1500m radius,

shoulder ballast of 600mm over a length of 100m on

either side of the common point should be provided Bursting Force f = P/R per m

P= 2 AE t


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PERMITTED LOCATIONS (Contd) GRADIENTS

STEEPEST 1 IN 100 VERTICAL CURVE IF ALGEBRIC DIFGFERENCE IS EQUAL TO OR

MORE THAN 4 mm/m OR 0.4 %,AS PER PARA 419 OF IRPWM

MINIMUM RADIUS BG MG

B 3000 m ALL ROUTES 2500 m C,D & E 2500 m

LWR/CWR PLAN REQUIRES THE APPROVAL OF

THOD. HOWEVER ANY DEVIATION FROM THEPROVISION OF THIS MANUAL APPROVAL OF PCESHALL BE OBTAINED


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TRACK STRUCTURE FOR LWR/CWR

NOTES Already existing on ST/CST with keys upto 130 kmph

on BG may be continued if satisfactory On ST/CST with keys, breathing lengths be preferablywith elastic fastenings

For CST 9 precautions as per annexure ii Existing on wooden sleepers with ACB & two way

keys or elastic fastenings may be continued

130 kmph for BG 100kmph for MG if satisfactory


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TRACK STRUCTURE FOR LWR/CWR SLEEPER DENSITY

TYPE OF SLEEPER SLEEPER DENSITY (BG/MG)PRC 1310 IN ZONE I & IIPRC 1540 IN ZONE III & IVOTHERS 1540 IN ALL ZONES

RAILS GAUGE RAIL SECTION

BG 90R/52 kg/60 kg

ALREADY LAID WITH 60R RAILS MAY BE CONTINUED

In one LWR two different rail sections are not permitted Any change in rail section isolate by SEJ

LWRs laid on PRC having two different rail sections oneither side of SEJ provide two 3 rail panels, one of each railsection with combination fish plated joint between the twopanels


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BEFORE CONVERSION USFD

Cropping of bent, hogged, battered, or having historyof bolt-hole cracks

As for as possible without fish bolt holes Fish bolt holes if any should be chamfered


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MISCELLANEOUS: 4.5.1 CONTINUITY OF TRACK STRUCTURE:

WHENEVER LWR/CWR IS FOLLOWED BYFISHPLATED TRACK/SWR, THE SAME TRACK

CONTINUED FOR THREE RAIL LENGTHS BEYONDSEJ.

4.5.2 LEVEL CROSSINGS:

LEVEL CROSSINGS SITUATED IN LWR/CWRTERRITORY SHALL NOT FALL WITHIN THE

BREATHING LENGTHS.


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4.5.3 POINTS & CROSSINGS :LWR/CWR SHALL NOT NORMALLY BE TAKEN

THROUGH P&C. THREE NORMAL RAIL LENGTHSSHALL BE PROVIDED BETWEEN SRJ AND SEJ ASWELL AS BETWEEN THE CROSSING AND SEJ.

PROVIDED WITH ERCS/ANCHORS TO ARRESTCREEP.

HOWEVER, WHERE PSC TURNOUTS ARE LAID,

INSTEAD OF THREE NORMAL RAIL LENGTHS, ONETHREE RAIL PANEL SHALL BE PROVIDEDBETWEEN SEJ AND SRJ AS WELL AS BETWEENHEEL OF CROSSING AND SEJ.


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4.5.4 GLUED JOINTS: G3L TYPE. 4.5.5 LOCATION OF SEJ:

Obligatory points such as level crossings, girderbrid es, oints & xin s, radients, curves and

insulated joints. SEJ with straight tongue andstock shall not be located on curves sharper than0.5 degree as far as possible. SEJ shall not belocated on transition of curves.


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BREATHING LENGTHMax. thermal force in each rail = AE t (i)Max. force in both rails = n * Rwhere, n = no.of sleepers in breathing length

R = longitudinal ballast resistance/sleeperIf r = longitudinal ballast resistance/m/rail and

L = breathing length;

Max. force in each rail = L b * r (ii) Lb*r = AE tOr, L b = AE t

r

For a 52kg rail, t = 48oC and r=1000 kg/m/rail Lb=78.64mL b A, t

1r


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Factors Affecting1. X-sectional area of rail (A)

2. Max. temp. variation (t)3. Longitudinal ballast resistance (r)

De ends on

i) type of sleeperii) packing conditioniii) ballast profileiv) passage of traffic

Ballast resistance per unit length of track remains more or

less constant for sleeper density of 1200 to 1500 per km.


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Longitudinal Ballast ResistanceLong.resistance

Gauge Sleeper (kg/m/rail)

BG PRC 1110ST 870Wooden 640CST- 650

MG Wooden 380ST 315CST-9 330

NB: The above values are approximate and depend on consolidation of ballast,ballast profile, type of ballast, etc.

Breathing lengths given in Annexure 1-B of LWR Manual.


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THERMAL MOVEMENTS

Free expansion = (dx) t

Contraction =Net expansion = (dx) t (dx)= (dx) (i)

EA

xP )(

EA

xP )(

xPP )(

where, P=AE t = max. force in LWRTotal expansion is obtained by integrating (i).[P-P(x)] (dx) = Area of shaded diagram

Commutative value of expansion/contraction, M = *Thus max. movement = Half the movement of Lb in free condition

Also, M =

2

** t L

AE

LPbb =

r

t AE

r

P

Lr

t AE b

==Q(2)(


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MINIMUM REQUIRED GAP AT SEJExample:-

Gauge = BGRail = 52Kg (A=66.15 cm 2)Sleepers = PRCr=1000 Kg/m/rail (assumed)E=2.15x10 6k /cm 2

=1.152 x 10-5

/ o

Ct=48 oC (max. expected drop in rail temp. from t d in zone IV)M=AE( t)2 = 21.74mm

2r

If two LWRs meet at point, M=43.48mmFor t=28 oC, ie.max.expected rise in rail temperature from td in Zone IVM=7.41mmThus, total range to be provided for free expansion and contraction in a

SEJ=2(21.74+7.41)=58.3mm


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DESIGNED GAP AT SEJs

Additional gap provided for

1. Creep of rails2. Incorrect setting of SEJ at the time of laying

3. Fracture

Separate drawings are available for SEJs in BG as well as

MG, for track on formation as well as for speciallocations, viz. bridge approaches.


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LAYING OF LWR/CWR(Contd.)

6. GAPS AT SEJ:

6.1 Gaps at SEJ shall be adjusted at the time oflaying/subsequent destressing of LWR/CWR. As

shown below and shall be as under:

Rail section laid Gap at td

52/60 kg 40mmOthers 60mm


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LWR Basics

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