Download - LWR Basics
-
8/11/2019 LWR Basics
1/53
LONG WELDEDRAILS
-
8/11/2019 LWR Basics
2/53
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
-
8/11/2019 LWR Basics
3/53
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
-
8/11/2019 LWR Basics
4/53
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
-
8/11/2019 LWR Basics
5/53
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
-
8/11/2019 LWR Basics
6/53
DEVELOPMENT OF RAIL WELDING IN
INDIA BUT LARGE SCALE MAINTAINACE
PROBLEMS Increased rail battering and hogging Bent fish plates
-
8/11/2019 LWR Basics
7/53
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
-
8/11/2019 LWR Basics
8/53
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.
-
8/11/2019 LWR Basics
9/53
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.
-
8/11/2019 LWR Basics
10/53
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.
-
8/11/2019 LWR Basics
11/53
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.
-
8/11/2019 LWR Basics
12/53
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.
-
8/11/2019 LWR Basics
13/53
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.
-
8/11/2019 LWR Basics
14/53
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.
-
8/11/2019 LWR Basics
15/53
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
-
8/11/2019 LWR Basics
16/53
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 )
-
8/11/2019 LWR Basics
17/53
-
8/11/2019 LWR Basics
18/53
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 )
-
8/11/2019 LWR Basics
19/53
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
-
8/11/2019 LWR Basics
20/53
-
8/11/2019 LWR Basics
21/53
-
8/11/2019 LWR Basics
22/53
-
8/11/2019 LWR Basics
23/53
-
8/11/2019 LWR Basics
24/53
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)
-
8/11/2019 LWR Basics
25/53
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.
-
8/11/2019 LWR Basics
26/53
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
-
8/11/2019 LWR Basics
27/53
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
-
8/11/2019 LWR Basics
28/53
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
-
8/11/2019 LWR Basics
29/53
-
8/11/2019 LWR Basics
30/53
gg
ggggg
-
8/11/2019 LWR Basics
31/53
-
8/11/2019 LWR Basics
32/53
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
-
8/11/2019 LWR Basics
33/53
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
-
8/11/2019 LWR Basics
34/53
TRACK STRUCTURE FOR LWR/CWR
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
-
8/11/2019 LWR Basics
35/53
TRACK STRUCTURE FOR LWR/CWR
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.
-
8/11/2019 LWR Basics
36/53
TRACK STRUCTURE FOR LWR/CWR
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.
-
8/11/2019 LWR Basics
37/53
TRACK STRUCTURE FOR LWR/CWR
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.
-
8/11/2019 LWR Basics
38/53
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
-
8/11/2019 LWR Basics
39/53
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.
-
8/11/2019 LWR Basics
40/53
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.
-
8/11/2019 LWR Basics
41/53
-
8/11/2019 LWR Basics
42/53
-
8/11/2019 LWR Basics
43/53
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)(
-
8/11/2019 LWR Basics
44/53
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
-
8/11/2019 LWR Basics
45/53
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.
-
8/11/2019 LWR Basics
46/53
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
-
8/11/2019 LWR Basics
47/53
-
8/11/2019 LWR Basics
48/53
-
8/11/2019 LWR Basics
49/53
-
8/11/2019 LWR Basics
50/53
-
8/11/2019 LWR Basics
51/53
-
8/11/2019 LWR Basics
52/53
-
8/11/2019 LWR Basics
53/53