LWR concept , hystersis and permitted location updated as per CS 10.pptx

Long welded rail Indian Railways

1. CONCEPT OF LWR

2. Gap at rail ends to cater for thermal expansion and contraction

3. THERMAL FORCES IN RAIL (335) Temperature changes cause expansion of the rail. If rail is restricted from expansion, thermal forces are built up within the Rail. The thermal force (P) is calculated by P = E A  t where, P = Thermal force in the rail (kg) E = Modulus of elasticity of rail steel ( 2.11 x 10 6 kg/sq.cm)  = Coefficient of linear expansion of steel ( 1.152 x 10 -5 / C ) A = Area of cross section of the rail (sq.cm) t = Variation of rail temperature from td /to ( C) This Thermal force is resisted by the track structure.

4. RESISTANCE TO THE THERMAL FORCE BY TRACK COMPONENTS (338) Resistance by the track (R) is due to Rails , which are fastened to sleepers with fittings Sleepers are embedded in Ballast Ballast is laid on stabilized formation and is well compacted Thus, a track with all its components, acts as a composite structure which offers resistance to the free expansion / contraction of rail on account of thermal forces .

5. Movement at Ends Unbalanced Force No Movement at Centre Portion Breathing Length Breathing Length CONCEPT OF LWR P r r Long Welded Rail (LWR) is a welded rail, the central part of which does not undergo any longitudinal movement due to temperature variations . P>R P>R P<R R at any point from the free end = r 1 +r 2 .…..+ r n

6. Long Welded Rail (LWR) is a welded rail, the central part of which does not undergo any longitudinal movement due to temperature variations. A length of greater than 250 metre on Broad Gauge (BG) will normally function as LWR .The maximum length of LWR under Indian conditions shall normally be restricted to one block section LONG WELDED RAIL (325) Understanding the delicate balance between the Thermal force, P and the Resistance offered by the track, R , at all times is the key .

7. DEFINITIONS Breathing Length is that length at each end of LWR/CWR, which is subject to expansion /contraction on account of temperature variations. Switch Expansion Joint (SEJ) is an expansion joint installed at each end of LWR/CWR to permit expansion/contraction of the adjoining breathing lengths due to temperature variations .

8. Rail Temperature is the temperature of the rail at site as recorded by an approved type of rail thermometer . This is different from ambient temperature which is the temperature of air in shade at the same place . Mean Rail Temperature (t m ) for a section, is the average of the maximum and minimum rail temperatures recorded for the section. Destressing is the operation undertaken with or without rail tensor to secure stress free conditions in the LWR/CWR at the desired/specified rail temperature. DEFINITIONS

9. MEASUREMENT OF RAIL TEMPERATURE The following are the types of approved thermometers for measuring rail temperature:- i) Embedded type - This is an ordinary thermometer inserted in a cavity formed in a piece of rail-head, the cavity filled with mercury and sealed. The rail piece, exposed to the same conditions as the rail inside the track. This type of thermometer takes 25 to 30 minutes for attaining temperature of the rail. ii) Dial type - This is a bi-metallic type thermometer, which is provided with magnet for attaching it to the rail. The thermometer is attached on the shady side of the web of the rail. A steady recording of the rail temperature is reached within 8 minutes. iii) Continuous recording type - It consists of a graduated chart mounted on a disc which gets rotated by a winding mechanism at a constant speed to complete one revolution in 24 hours or 7 days as applicable giving a continuous record of rail e is temperature. The sensing element is attached to the web of the rail and connected to the recording pen, through a capillary tube which is filled with mercury. iv) Any other type of thermometer approved by RDSO/Chief Engineer . Where a number of thermometers are used to measure the rail temperature at one place, as in case of laying of LWR, de-stressing etc. or during routine tools inspection at office of SSE/ P Way any of the thermometer showing erratic readings, appreciably different from the other adjoining thermometers, shall be considered as defective.

10. Destressing temperature(t d ) (335) is the average rail temperature during the period of fastening the rail to the sleeper after destressing LWR/CWR without use of rail tensor. If rail tensor is used, t d , for all practical purpose is equal to t , which is the rail temperature at which the rail is free of thermal stress. Range of t d or t shall be within the limits of the rail temperature shown below. Temperature zone I,II&III For all rail sections t m to t m +5°C Temperature zone IV i )52kg and heavier t m +5°C to t m +10°C . DEFINITIONS

11. Prevailing Rail Temperature (t p ) is the rail temperature prevailing at the time when any operation connected with destressing is carried out. Stress-free Temperature (t o ) is the rail temperature at which the rail is free of thermal stress. When tensors are utilised for the destressing operation the work has to be carried out at t p , which shall be lower than stress-free temperature . DEFINITIONS

12. Hot Weather Patrol (1005(1)) is the patrol carried out when the rail temperature exceeds (i) Td +30 °C on wider sleeper with sleeper density of 1660 no./km ( ii) td + 25°C on PSC sleeper track with sleeper density 1540per km and above. (iii) td+20°C on PSC sleeper track with sleeper density less than 1540 per km and track other than PSC sleeper. Cold Weather Patrol (1005(3)) is the patrol carried out during cold months of the year in specified sections as per instructions of Sr. DEN Co . DEFINITIONS

13. Consolidation of Track (337(5)) is the process of building up ballast resistance to the tendency of movement of sleeper either initially before laying LWR or making up subsequent loss of resistance by anyone of the following:- i) For the track structure consisting of concrete sleepers, passage of at least 50,000 gross tonnes of traffic on BG or a period of two days whichever is later. ii) At least one round of stabilisation by Dynamic Track Stabiliser (DTS). iii) For newly laid LWR/CWR, at least three rounds of packing, last two of which should be with on-track tamping machines . DEFINITIONS

14. PERMITTED LOCATIONS IN LWR

15. PERMITTED LOCATIONS (326) 1.GENERAL CONSIDERATIONS FOR LAYING LWR/CWR New constructions /doublings /gauge conversions / retired alignment / permanent diversion shall be opened with LWR/CWR. CTR (P) / TSR(P) / TRR(P) shall provide for LWR/CWR wherever permissible. Also existing rails on permitted locations may be converted into LWR/CWR, provided they meet the requirements for Welding of Rail Joints by Alumino -Thermic (SKV Process) / Flash Butt Process, as the case may be. In yard lines, rail joints may be welded to form LWR if the condition of all the components of track is generally sound and without any deficiency, subject to such relaxation as may be approved by Chief Engineer, in each specific case .

16. PERMITTED LOCATIONS (326) LWR/CWR shall not be laid on curves sharper than 440 m radius. However, in temperature zone-I LWR/CWR may be laid on curves up to 350metre radius (5°curve) on BG with following additional precautions i ) Minimum track structure should be 52kg rail on PSC sleeper, 1540 sleeper density with 300mm clean ballast cushion. ii) Shoulder ballast for curved sharper than 440m radius should be increased to 600mm on out side of curve for 100m beyond tangent point. iii) Reference marks should be provided at every 50 m interval to record creep if any. Each curve of length greater than 250 m should be preferably provided with SEJ on either side .SEJ should be located in straight track at 100 m away from tangent point

17. PERMITTED LOCATIONS: (326) 326(2)(b) REVERSE CURVE: LWR/CWR may be continued through reverse curves. Shoulder ballast of 600mm over a length of 100 m on both side of the common point of a reverse curve would be provided. In case there is a straight track between the reverse curves, this 100m would be considered from the center of the straight track. No such measure would be required if the length of straight track between the reverse curves is more than 50 m. The steepest Gradient permitted shall be 1 in 100. Installation of LWR / CWR – or change in its constitution at a later stage with preparation of a detailed LWR plan - Approval of CTE is required Approval of PCE: For Any deviations from the provisions of LWR manual, approval of PCE is required

18. PERMITTED LOCATIONS (326) (5) (a) FORMATION – LWR/CWR shall be laid on stable formation having stipulated formation width and ballast cushion (below the bottom of the sleeper); and with approved PSC sleepers and its matching fastening system. (b) The minimum rail section to be used shall be of 52 kg/m. (c) In a LWR/CWR, two different rail sections are not permitted. (d) In case of LWRs laid on concrete sleepers having different rail section on either side of SEJs, combination SEJ to RDSO Drg. No T-6782 (52kg / 60 Kg) shall be provided. Alternatively, two 3 rail panels (39 m), one of each rail section shall be provided with combination fish plated joint, between the two panels. (e) New rails used in LWR/CWR shall, as far as possible, be without fish-bolt holes. (f) Bolt holes, if any, shall be chamfered.

19. (6) Wherever LWR/CWR is followed by FP/SWR, the same track structure as that of LWR/CWR shall be continued for at least three rail lengths (39 m) beyond SEJ. (7) Level crossings situated in LWR/CWR territory shall not fall within the breathing lengths. (8) Points and Crossings: (a) If LWR is terminated near P&C, one three rail panel (39 m) shall be provided between SRJ and SEJ as well as between the crossing and SEJ. This length shall be provided with elastic fastenings with adequate toe load to arrest creep. (b) In case, LWR/CWR is taken through P&C, the provisions contained in RDSO report no. CT-48 shall be followed . PERMITTED LOCATIONS (326)

20. Vertical curve (417) shall be provided at the junction of the grade when algebraic difference between the grades is equal to or more than 4mm per metre or 0.4 percent 327 - All insulations for track circuiting in LWR/CWR shall be done by providing glued joints of G3(L) type. 328 The exact location of SEJ shall be fixed taking into account the location of various obligatory points such as LC, bridges, P&C, gradients, curves and insulated joints. The conventional SEJ (RT-4160 and RT-4165) with straight tongue and stock shall not be located on curves sharper than 0.5° The improved SEJs (RT-6902, RT-6914, RT-6922, RT-6930) may be located on curves up to 2°. SEJ beyond 2° and up to 4° shall be laid with approval of PCE in consultation with RDSO (3) The SEJ shall not be located on transition of curves.

21. 329 Bridges with ballasted deck ( without bearing ): can be continued over bridges without bearings like slabs, box culverts and arches. 330 Bridges with Ballasted Deck & BLT - ( with bearing ) Detailed calculations be done by Design office of Chief Bridge Engineer / CAO (C) to ascertain the effect of LWR on such bridges and its effect on the sub-structure of the bridge as per Para 2.8.1.2 of “Bridge Rules”. LWR / CWR may be permitted on a case-to-case basis based on the above calculations. In case detailed calculations are not done, LWR on ballasted deck bridges (with bearings) may be permitted as per Para 331 below for bridges with un-ballasted deck. The LWR / CWR on BLT Bridges may only be permitted, if found satisfactory on the basis of above calculations. CBE / CAO (C) may further permit use of special arrangements to control RSI effects as stipulated in the RDSO report no. BS-114. LWR ON BRIDGES

22. TEMP. ZONE RAIL SECTION RAIL FREE FASTENING ON BRIDGE WITH PRC SLEEPERS ON APPROACHES - SINGLE SPAN NOT EXCEEDING 30.5 METRE, HAVING SLIDING BEARINGS ON BOTH ENDS I 60KG 30 52KG 45 II 60KG 11 52KG 27 III 60KG 11 52KG 27 IV 60KG 11 52KG 27 (a) Rail-free fastenings shall be provided throughout the length of the bridge between abutments. (b) SEJ of the LWR should be located such that bridge does not fall in the breathing length of the LWR. The approach track upto 50 m on both sides shall be well anchored by providing PRC sleepers with elastic rail clips with adequate toe load so as to arrest creep. (c) The ballast section of approach track upto 50 metre shall be heaped upto the foot of the rail on the shoulders and kept in well-compacted and consolidated condition during the months of extreme summer and winter. Bridges with Unballasted Deck - Case – 1 LWR ON BRIDGES (331)

23. (a) Central sleepers to be anchored with anchoring arrangement (two each in end spans & one each in the middle spans) as per RDSO Drg. No. M-10920(1) , the remaining sleepers to be with rail-free fastenings. (b) The track structure in the approaches shall be same for case 1. (c) The girders shall be centralized with reference to the location strips on the bearing, before laying LWR/CWR. (d) Sliding bearings to be inspected during the months of March & October each year and cleared of all foreign materials. Lubrication of the bearings shall be done once in two years. TEMP. ZONE RAIL SECTION RAIL FREE FASTENING ON BRIDGE & PARTLY BOX ANCHORED, SINGLE SPAN NOT EXEEDING 30.5 M AND SLIDING BEARINGS ON BOTH ENDS I 60KG 77 52KG 90 II 60KG 42 52KG 58 III 60KG 23 52KG 43 IV 60KG 23 52KG 43 Bridges with Unballasted Deck - Case – 2 LWR ON BRIDGES (331)

24. LWR/CWR may also be continued over a bridge with SEJ at the far end approach of bridge using rail-free fastenings over the girder bridge. The length of the bridge will be restricted by the capacity of the SEJ to absorb expansion, contraction and creep, if any, of the rails . ( i ) SEJ is to be installed 15 metre away from the abutments. (ii) lmproved SEJ with 2 gaps of 65mm (max.] each (Drawing no. RDSO/T-6922 and RDSO/T-6930) may also be used for laying at far end approach of bridges in lieu of IRS design SEJ with 120 mm max. gap . Bridges with Unballasted Deck - Case – 3 Rail temp zone Max. movement of SEJ used (mm) Maximum Length of bridge Initial gap to be provided at t d With PRC approach sleepers IV 190 55 m 7.0 cm III 70 m 7.0 cm II 110 m 6.5 cm I 160 m 6.5 cm II 120 20 m 4.0 cm I 50 m 4.0 cm LWR ON BRIDGES (331)

25. In case of LWR is continued over bridges as per Case 3 above, the measurement of gaps of stock rail / tongue rail tip of SEJ provided at bridge approach from the reference post shall be compared with the theoretical gaps as prescribed in Annexure - 3/9A . Bridges with Unballasted Deck - Case – 3 Bridge with SEJ at the far end approach of bridge (15m away) LWR ON BRIDGES (331)

26. W elded rails may be provided from pier to pier with rail-free fastenings and with SEJ on each pier. The rail shall be box-anchored on four sleepers at the fixed end of the girder if the girder is supported on rollers on one side and rockers on other side. In case of girder supported on sliding bearings on both sides, the central portion of the welded rails over each span shall be box-anchored on four sleepers . Bridges with Unballasted Deck - Case – 4 LWR ON BRIDGES (331)

27. Welded rails may be provided over a single span bridge, rail free fastenings & 190mm gap SEJs at 30 m away from both abutments. If bridge is supported on rollers on one side & rockers on other side, Rail shall be box anchored on four sleepers at the fixed end of bridge. If bridge is supported on sliding bearings on both sides, the central portion of the welded rails shall be box anchored on four sleepers. The approach track upto 50 m on both sides shall be well anchored by PRC sleepers with elastic rail clips with minimum toe load as specified. The installation temperature of such welded panels shall be equal to t m Temp Zone Max Length of single span girder bridge I 146 m II 110 m III 87 m IV 75 m Bridges with Unballasted Deck - Case – 5 LWR ON BRIDGES (331)

28. In case welded rails are provided as per Case (4) or (5) above (welded rails only and No LWR), these shall not be entered in TMS as LWR and accordingly, measurement of gaps of at such SEJs of welded panels is not warranted. W elded rails on Bridges Bridges with Unballasted Deck - Case – 4 & 5 LWR ON BRIDGES (331)

29. PERMITTED LOCATIONS (326) LWR / CWR on Ballast Less Track (BLT) LWR / CWR - on BLT with approved matching fastening system with minimum in-service longitudinal rail restraint of 15 KN/m/rail. Test plan & Technical criteria of fastening system is as laid down. ii) Minimum rail section to be used shall be 60 Kg/m. iii) C urves up to 350 m radius, S teepest gradient 1 in 80. iv) At the junction of BLT and Ballasted track, transition of suitable design - to smoothen the change in stiffness of track from BLT to ballasted track. To improve the lateral stability of ballasted track on the approach of BLT at junction, a suitable ballast retaining wall shall be provided for a length of 100 meters from the junction of BLT and ballasted track.

30. PERMITTED LOCATIONS (326) LWR / CWR on Ballast Less Track (BLT)   v) In case LWR / CWR on BLT is to be isolated from ballasted track due to field constrains, SEJ provided in the ballasted track at minimum distance of 30 m from the junction of BLT and ballasted track. vi) The movement of SEJ towards BLT is governed by the effectiveness of fastening on BLT. Longitudinal track resistance of BLT is more than ballasted track, therefore movement of SEJ will be less for LWR / CWR on BLT as compared with movement at SEJ for LWR / CWR on ballasted track. Gap at SEJ towards BLT shall be compared with the values given in Annexure-3/9. If the movement at SEJ reaches the limits prescribed in Annexure-3/9, the effectiveness of fastenings on BLT shall be checked by measuring the clamping force.

31. PERMITTED LOCATIONS (326) LWR / CWR on Ballast Less Track (BLT) vii) The creep of LWR / CWR track in ballasted track approach at the junction with BLT shall be monitored up to a length of 500 meters by providing creep post at interval of 100 m. If the creep exceeds 10 mm in 500 m length, ballasted track shall be destressed for a length of 1000 m

32. CONCEPT OF HYSTERSIS IN LWR