Friday, March 30, 2018

Laying of Sleepers

Locations where Concrete Sleepers are used-

Concrete sleepers should normally be used only with LWR/CWR track. Hence the condition for laying LWR/CWR should equally apply for laying concrete sleepers.

Use of concrete sleepers on long lengths of track where provisions of check rails or guard rails is necessary, is prohibited unless special arrangements are made to
provide the necessary flange way clearance.

Where concrete sleepers are used in yards with fish - plated track, the sleeper spacing at fish plated joint shall be kept uniform. In addition 1m long fish plates may preferably be provided at such joints. (Cs.No102)

Conditions for laying Concrete Sleepers:

i) Track should be deep screened.
ii) Cuttings having rocky bed should have clean ballast cushion of at least 300  mm.
iii)On Arch bridges formation cover min. 1 m.
iv) On other bridges ballast cushion not less than 300 mm.

Laying of Concrete Sleepers –

Concrete sleepers are heavy and manual handling is not only difficult but may even cause damage to the sleepers. Mechanical handling of concrete sleepers, therefore, becomes necessary. For this purpose, the Mechanical Relaying Systems consisting of portal cranes are used. Normally a set will consist of two portal cranes.

Operations connected with Relaying–

(1) Preparatory work at site of relaying

(a) Since concrete sleepers are laid with LWR/CWR all preparatory works as listed in LWR Manual should be carried out before laying concrete sleepers. In addition, longitudinal section showing the existing rail levels should be plotted and proposed rail level determined taking into consideration the following points :–

(i) 300mm. ballast cushion is available below the concrete sleepers.
(ii) Clearances to structures are maintained within the accepted limits. 
(iii ) The track and the road surface are suitably raised and approaches regraded. (iv) Where lifting of track is not possible at places like-below over line structures, on girder bridges and in yards, etc., suitable ramping out should be done.

(b) The proposed predetermined rail level should be indicated at suitable intervals along the tracks.

(c ) Auxiliary track should be laid at 3.4 M. gauge keeping its centre line same as that of the existing track.

(d) The existing welded rails should be converted into panels of suitable lengths such that the capacity of the portal crane is not exceeded by handling the old panel.

(2) Pre-assembly of Panels –

Sleepers received from the Concrete Sleeper plant are unloaded and stacked at the base depot. Handling of Concrete Sleepers is done by portal cranes or separate cranes provided for the purpose. These sleepers are assembled into panels making use of service rails. While assembling the panels, elastic fastenings complete in all respects should be provided and correct uniform spacing of sleepers should be ensured. The assembled panels are stacked and are later loaded in BFRs in three to four tiers.

Formation of relaying train –

The relaying train shall consists of two empty BFRs for loading released track panels, adequate number of BFRs loaded with pre assembled panels, BFRs loaded with portal cranes, one equipment and tool van, one crew rest van, one brake van and an engine.

Actual Relaying –

 At speed restriction of 20 km. p. h. is imposed at the place of relaying and preliminary works such as loosening of fastenings, removal of ballast etc. are carried out in advance. On the day of relaying, traffic block is imposed and the relaying train enters the block section. After the relaying train is positioned, the portal cranes unload by themselves on the auxiliary track. The old track is dismantled and loaded by the portal cranes on the empty BFRs. The ballast is then leveled and the pre assembled panels are laid in position. The new and existing tracks are joined by closure rails. After the last panel is laid, a ramp is made in two rail lengths between the existing track and the new track, to run out the difference in levels. The relaying train returns to the base depot where the old track panels are unloaded. 

(5) Post relaying works –

In subsequent blocks the service rails should be replaced by welded panels. The  newly laid track is tamped and speed restrictions relaxed in stages as per schedules mentioned .Before relaxing the speed to normal, provisions of proper L.W.R. ballast profile should be ensured.

Procedure for Manual Laying –

(1)Manual Laying will not normally be adopted except under exceptional circumstances.
(2) Loading and Unloading –
(a) Concrete sleepers shall be placed perpendicular to the length of the BFR.  
(b) Manual unloading shall be done sleeper by sleeper. Wooden sleepers provided with hooks at the top ends for gripping the side of the BFR shall be used as ramps for sliding the sleepers down to the cess level. Damage by over-running shall be prevented by placing the lower ends of the ramps either inside an old motor truck tyre or between gunny bags filled with wood shavings and the sleeper allowed to move down the ramp. Two men shall stand on the cess with crowbars planted into the cess and control the downward sliding of the concrete sleepers 
(c) After unloading, the sleepers shall be placed on the cess approximately alongside the final position. Where the width of the cess is sufficient, the concrete sleeper should be kept supported by wooden blocks so as to be approximately at the same level as in its final position in track. Individual concrete sleepers may be transported conveniently on a rail dolly to R.D.S.O. Drawing No.MA.3031.

Laying Procedure –

The following procedure shall be adopted for manual laying of concrete sleepers in place of existing fish-plate track:

(a) Just prior to the line block, a speed restriction of 25 km./h. shall be imposed on  the portion to be re-laid during the block and rail sleeper fastenings shall be removed from the alternate sleepers. Ballast cribs between sleepers shall be exposed upto bottom level of sleepers. It shall be ensured that the number of sleepers taken up for replacement during the line block period shall not be more than that which can be given at least one mechanical tamping with ‘on track’ tamper before the first train is allowed after the replacement of the sleepers. 

(b) After taking the line block, the rails over the length to be dealt with during the line block period shall be disconnected and removed. The sleepers shall then be taken out, taking care to disturb the ballast bed only to the minimum extent.

(c ) The new concrete sleepers shall then be laid in position by means of sleeper slings taking care to ensure the correct longitudinal and lateral alignment. When the sleepers are being placed in position, the prepared ballast bed should be disturbed only as little as possible. Care should be taken not to damage the edges of the sleepers or to chip the concrete. After the sleepers are placed, rubber pads shall be placed at the rail seats. Elastic clips shall be loosely fastened at this stage. If the original rails are to be continued after relaying, the track rails shall be laid and connected on either side.

(d) After the sleepers are packed, the rails shall be secured in position by inserting the insulators and elastic fastenings and firmly fastened.

Maintenance of concrete sleeper track –

(1) General

(a) Concrete sleeper track should be maintained by heavy on-duty track tampers.
(b) An annual machine deployment programme shall be drawn by zonal railway and be circulated to the divisions before the beginning of the year.
(c) For spot attention/slack picking, multipurpose Tampers and Off-track Tampers shall be used as a regular measure on Concrete Sleeper Track, in the following  areas of application:

(i) Picking up slacks in isolated stretches.
(ii) Points and Crossing areas,
(iii)Approaches to bridges and level crossings,
(iv)Buffer rail joints/glued joints in LWR section,
(v) Block insulated joints/glued joints in track circuited stretches. For Off-track
tampers, the working instructions, issued by Railway Board/RDSO as amended
from time to time, should be followed. As an interim measure, where Off-track
tampers are not available, the packing may be done with the help of Crowbar/
Beater, duly taking care that the concrete sleepers are not damaged.
(d) Pre-tamping, during tamping and post tamping attentions should be given to
track as indicated in Para 226. (For further details, Chapter 3 of Indian Railways
Track Machine Manual may be referred to).

(2) Annual Systematic Attention on PRC track In addition to machine tamping, the gangs will carry out annual systematic attention to track from one end of gang beat to the other during work season. This will include –

(a) Examination of rails, sleepers and fastenings including measurement of toe load of ERCs.
(b) Inspection of and attention to insulated joints, switch expansion joints etc.
(c) Packing of approaches of bridges, level crossings, breathing lengths of LWRs and  bad formation areas etc.
(d) Shallow screening of track.
(e) Through packing of track not maintained by machine, e.g. tracks not on PSC
sleepers including all running lines of the yards and points and crossings in such
running lines.
(f) Minor repairs to cess of bank.
(g) Boxing and dressing of ballast.
(h) Replacement of damage/missing rubber pads, liners and ERCs.

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