Track renewal or track re-laying work can be done either manually or by mechanical means. These works involve the following steps.
(a) Survey of the section
(b) Preliminary works
(c) Actual execution of track renewal works
Survey of the Section
The section to be re-laid should be surveyed in advance. The survey includes the preparation of the longitudinal sections of the track, including the existing rail levels, at every 100 m and at obligatory points such as level crossings, road over bridges, and overhead crossings. The cross sections are taken at every 50 m in station yards and on platform lines, at the site of foot over bridges, overhead watering arrangements, etc.
Preliminary works are the minor works undertaken prior to the actual work involved in track renewal. These works include the following tasks.
(a) Unloading track materials
(b) Ballasting the section
(c) Fixing level and centre-line pegs
(d) Arranging traffic blocks
Each one of these preliminary works is briefly discussed here.
Unloading track materials It should be ensured that the relevant materials are unloaded at the precise location where they are to be laid, as explained in the following.
Rails These should be unloaded in pairs on the cess on either side of the track in the case of single-line sections and between two tracks in the case of double-line sections.
Sleepers The sleepers are taken directly to the site in wagons and unloaded on the section. They are piled in small stacks and subsequently laid at their final location. Alternatively, they are laid 'end on' with respect to their future location, wherever possible.
Fittings Small fittings are likely to be lost or stolen. These should, therefore, be unloaded in depots, gang huts, gate lodges, etc., and taken to the site as and when required. New fish plates are graphited and fish bolts and nuts are oiled and lubricated before use.
Ballasting the section An adequate quantity of ballast is provided in advance and is unloaded at the site, preferably with the help of ballast trains. Some of the ballast can also be collected, or even procured, at the cess to avoid ballast deficiency. The ballast should preferably be deep screened in advance.
Fixing centre-line and level pegs Centre-line and level pegs are provided at every 50 m.
Arranging traffic blocks The arrangement of traffic blocks should be finalized in consultation with the operating department. A joint memorandum of understanding should be prepared for drawing up the exact programme of traffic blocks.
Actual Execution of Track Renewals Work
Once the preliminary works are completed, the actual work of track renewal can start. This involves the following tasks.
Setting up traffic block A traffic block of about 2 to 4 hours is set up in order to execute the work of track re-laying.
Dismantling old track The old track is dismantled by removing the fish-bolts and fish plates as well as the sleeper fastenings. The old rails and sleepers are then removed and stacked on the side of the track opposite the new material.
Deep screening The ballast should be deep screened if this was not done earlier along with the other preliminary works. The ballast should be dressed and properly levelled in accordance with the correct profile.
Linking new track After the ballast has been laid in keeping with the correct level, the sleepers are laid almost in their correct places, and the rails are linked over them using proper expansion liners.
Packing new track The track is then lifted to the correct level, aligned, and packed either manually or with the help of machines.
Progress and Output
On an average, the renewal of about 0.4 km of track can be achieved by 15 to 30 gangs in a 3 to 4 hour traffic block. The deep screening of the ballast should, however, have been completed ahead of re-laying work.
The rail dolly (Fig. 21.3) is an equipment used for the quick and easy transportation of rails. It consists of a tabular frame fitted with a chain that ends in a rail clamp. There are two double-flanged wheels with ball bearings, which run on rails. A leverage handle is available for operating and moving the rails. The equipment, weighing about 55 kg, is extremely useful for carrying rails and sleepers to the site
of work. In the event of an approaching train, the rail as well as the equipment can be cleared off the track within 10 seconds.