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लॉन्ग वेल्डेड रेल्स Long Welded Rails

LWR1)2) or LONG WELDED RAIL IS ONE IN WHICH THE CENTRAL PART OF IT DOES NOT UNDERGO (PREVENTED FROM) EXPANSION AND CONTRACTION maximum length of LWR is block section to block section as per latest change there is provided one SEJ for expansion and contraction in it. LWR Track is fit for high speed route.In it there are very less chances of derailment.

एल डब्लू आर के फायदे Advantages of LWR

  1. To eliminate fish plated joint.
  2. To decrease wear and tear.
  3. To avoid cracks which develops from bolt holes.
  4. To save maintenance cost 25 to30%
  5. To decrease wear and tear 5% of rolling stock
  6. To decrease fuel consumption 7%
  7. To increase passenger comfort.

Evolution of LWR

  1. To know the correlation between the rail temp.and ambient temp.
  2. Dream of jointless track.
  3. Increase the length of rails by rolling larger from 13M to 380M.
  4. Standard measurement for rail temp.
  5. Thermal stresses
  6. To obtaining data from weather office for 90 year of 180 stations.
  7. Constraint expansion and contraction.
  8. Confirmation of lateral stability due to sleeper,fastening and ballast resistance.

What is shown in map of India outside and inside? Outside-Range of temp.rail and inside mean temp.

एल डब्‍ल्‍यू आर क्‍या होता है्?‍ What is LWR? It is welded rail in which central part does not undergo any longitudinal movement due to temperature variation. The portion that undergoes expansion and contraction is known as breathing length.

What is CWR? Continuous welded rail or CWR is an LWR that continues through the yards.


(a) Destressing must be done well in advance before summer season when rail temp is as below:-

  • 52 Kg & Heavier section : tm + 5 to tm + 10
  • other sections : tm to tm + 5

(b) Destressing is required to be done based on SEJ's behavior and gap as below

(i) differs beyond specified limits i.e.40mm for 52/60 Kg. and 60mm for others

(ii) exceeds maximum designed gap

(iii) stock/tongue rail tips crosses mean position.

Destressing is required to be done after major repair work like deep screening, lifting of track, realignment of track,Restoration of track,and laying of new track. It is also to be done if no. of rail-fracture location exceed 3 per Km.

© Ballast profile should be maintained properly in good condition and kept fully boxed.

(d) For regular maintenance rail-temperature should be as below :-

td +10 to td-30, and work should be completed well before onset of summer.

(e) Speed restriction is imposed if rail temperature after maintenance operation exceeds td+20 during the period of consolidation. Speed restrictions are

  • for BG - 50 KMPH
  • for MG - 40 KMPH

(f) Not more than 30 sleepers spaces is to be opened at a time for through packing or shallow screening.Remaining portion is to be tackled after passage of traffic for 24 hours in case of BG route carrying traffic greater than 10 GMT. For other route of BG/MG, it is taken after passage of traffic for two days.

(g) Slewing required for alignment correction,shoulder ballast should be removed from end only, to prevent chances of buckling if any. If crib ballast is required to be opened, shoulder ballast to be put again in position and the opened. For renewal of sleeper at specified location, called casual renewal. it should be tried only one sleeper at a time in 30 consecutive sleeper.If more than one sleeper is required to be replaced, it can be done after renewal of one sleeper and complete packing the ballast. At the same time observance of maintenance temperature is must.

(h) For fastening renewal, fastening of one sleeper should be handled at a time. If fastening of more than one sleeper is to be renewed then between the sleeper to be handled, 15 sleeper spaces should be left intact in position. For renewal of fastening requiring lifting of rail, like renewal of grooved rubber pad, one sleeper should be handled at a time. if more then one sleeper to be handled then at least 30 sleeper spaces should be left intact in position.

(i) Keyman should keep watch on the gap at SEj during daily inspection. it should be maintained for requirement like aligning, greasing, fitting in position and packing fortnightly. If buffer rail is used in lieu of SEJ it should be attended for lubrication twice in a year. Gap in fish-plated joints should be 3mm -12mm.

(j) If mechanized maintenance if employed in LWR track requiring lifting, a general lift should not exceed 50mm in PSC sleeper and 25mm in case of metal/wooden sleeper. Lifting requiring more the above lift should be done in stages with adequate consolidation period between the successive stages of lifting.

(k) After through fitting renewal(TFR) and deep-screening,if rail-temperature is between td+10 to td-20, temporary distressing is not required. But if rail-temperature is outside range given above, temporary destressing is required to be done at temperature below 10 c then temperature likely to attain during the period. Deep-screening should be followed by packing machine (DTS/TTM) at onset simultaneously.Also the track should be distressed as early as possible.

(l) During special work like major realignment of curve,through sleeper renewal, rehabilitation of formation or bridge-work the effected length of LWR should be separated from the main LWR by buffer-rail , and after work it should be continued and distressed.

Buckling of Track

If the rails are slender elements and when subjected to compressive forces, the track tends to buckle unless restrained by the weight of track and the lateral resistance offered by ballast. If the track loses lateral resistance due to any of the reasons:

  • Improper destressing
  • Jammed Switch Expansion Joint (SEJ)
  • Stress Free temperature quite low as compared with the prevailing temperature
  • Attention to track affecting lateral ballast resistance
  • Lifting of track for any reason

Buckling is a very serious occurrence for track and the safety is immediately jeopardised if a train passes over buckled track or track which is about to buckle (Incipient buckling condition). Hot weather patrolmen and p-way officials on track have to vigilant to look out for signs of buckling.

A couple of photographs of buckled track in one foreign railway are shown below:

C:/wamp/www/doku/data/pages/lwr.txt · Last modified: 2010/11/26 04:38 by iricen