Criterion for Classification
Track with speed potential Of 75 Kmph and traffic density between 1.5 – 2.5 GMT
Group 'Q' routes are those with maximum speed of more than 75 Kmph and 'R1' routes are those with speed potential of 75 Kmph and traffic density of more than 5 GMT. There are no such routes in SCR.
Group 'R3' route with route of 175.93 kms are slated for conversion to Broad Gauge.
In order to keep pace with the increasing traffic on various routes and also to take care of the heavier axle loads of rolling stock, Track Modernisation had been taken up as a thrust area in South Central Railway. As a part of track modernisation, heavier track structures are provided by way of provision of higher poundage and Ultimate Tensile Strength (UTS) rails on pre-stressed concrete sleepers with elastic fastening devices.
Track Modernisation mainly involved the following areas:
Use of heavier poundage rails
Provision of Pre-stressed Concrete (PSC) sleepers
Provision of increased clean ballast cushion
Provision of PSC sleepers in track junctions
Welding of rails to form long continuously welded rails of 3 kms or more in length.
Welding of rails in-situ by making use of Mobile Flash butt plant.
Use of Heavier Poundage Rails
Prior to track Modernisation, rails with weight of 90 lbs. Per metre and 75 lbs. Per metre with Ultimate Tensile Strength (UTS) of 72 Kg/mm were in use. In order to facilitate higher speeds and haulage of heavier wagons, heavier rails of 60 Kg/m and 52 Kg/m weight with UTS of 90 Kg/mm are being used while replacing existing rails. SCR has already got 6603.613 km of track replaced with these 52/60 kg/m rails of 90 UTS.
Provision of Pre-stressed Concrete (PSC) Sleepers
In SCR, as part of track Modernisation, out of a total BG running track kilometres of 7683.011 kms, 7544 Kms. of track has already been provided with pre-stressed concrete sleepers. 10 concrete sleeper plants are functioning on South Central Railway to cater the requirement of PSC sleepers for new lines, doubling and renewals.
Provision of Increased Clean Ballast Cushion
Stone ballast provided in the track affords resilience and stability to the track, resulting in improved ride quality. As a part of modernisation, the ballast cushion below the bottom of sleepers have been increased from about 150 mm, existing earlier, to about 300 to 350 mm, after laying of PSC sleepers.
Provision of PSC Sleepers in Track Junctions
Track junctions (turnouts), which are provided in station yards were earlier provided with wooden sleepers and steel sleepers. In view of the higher traffic density and also to conserve precious forest resources, SCR has gone in for provision of pre-stressed concrete sleepers for turnouts in station yards as a priority area in track Modernisation. So far, 4926 points and crossings on BG running track have been renewed with pre-stressed concrete sleepers. Every year about 300 turnouts with PSC sleepers are being provided in the place of existing wooden/steel sleepers.
Welding of Rail Joints
Individual rails rolled in India are of 13/26 metre length. Rails, when laid in track can be joined either by provision of fish plates or by welding the rail joints. Fishplated joints in track contribute to heavy noise and bad running as wheel has to jump across the gap at the joint. Hence welding of rails is done to convert the rails panels into long or continuous welded rail panels of a few kilometres length. These panels are called Long Welded Rails (LWRs) or Continuous Welded Rails (CWRs).
Welding of rails for conversion into LWRs/CWRs is another priority area in Track Modernization as this will facilitate smoother riding and also reduce the maintenance effort. Out of total BG running track kilometers of 7630.321 in SCR, the track in a length of 7500 Kms has so far been converted into LWR/CWR.
Welding in SCR is done by two methods:
Flash Butt Welding
Alumino-Thermic (AT) Welding
Flash Butt Welding
The individual rails of 13/26 m. length received from steel rolling plants are initially sent to Flash Butt Welding Plant at Moula_Ali, Secunderabad. The individual rails are then welded into rail panels of 20/10-rail length by flash butt welding technique.
Flash butt welding technique involves pre-heating of rail ends by passing high ampere low voltage current and then the rail ends are cyclically brought closer and separated, which results in heavy sparking between the rail ends. After the rail ends are brought to a molten state, butting of rail ends is done under pressure.
Flash butt joints have very high fatigue strength and are preferred to other types of welds. The rail panels of 10-rail length and 20-rail length formed by flash butt welding are transported from the Flash Butt Welding Plant to the field locations by loading into specially designed railway flat wagons. These panels are unloaded at the site through specially designed end unloading chutes fitted to the rearmost wagon.
Adoption of Flash butt welding technique in site using Mobile flash butt welding plant is taken up on South Central Railway, which will improve reliability of weld joint there by safety and improve riding conditions.
Alumino Thermic (AT) Welding
AT Welding is basically a field technique, wherein the joints in the 10-rail panels are welded in the track to convert into LWR/CWR. In AT Welding, specially fabricated dry clay moulds are fitted to the rail ends to be welded, duly creating a gap of 25 mm between the rails. The gap is filled by pouring hot molten metal into the mould of the same metallurgical composition, as that of the parent rail material.
Testing of Rails/Welds by USFD
Monitoring and maintaining the integrity of rail/Weld sections during their service life is paramount for ensuring safety of track and increasing asset life. The rails and welds in track are periodically tested by Ultra Sonic Flaw Detection (USFD) technique to detect any incipient minor flaws caused due to the passage of traffic and prompt remedial action taken in case of detection of any flaws.Additional precautions by way of joggling the doubtful and outraged welds is also being done so that the safety at welded joint is ensured.
Due to the passage of continuous traffic, track parameters slowly get altered and a few bad running locations get formed at isolated locations. Monitoring of the track in terms of track parametres and riding quality is done on a continuous basis by the following means:
Inspections by Maintenance Organisation
Objective measurement of track parameters by Track Recording Cars (TRCs)
Determination of riding quality using Oscillation Monitoring System (OMS)
Inspections by Maintenance Organisation
Inspections in the locomotives of fast express/mail trains are done by maintenance Engineers periodically to identify locations of bad running which are promptly attended to. The Maintenance Engineers do physical inspection of track at periodical intervals by travelling along the track in trolleys, either motor powered or pushed manually. During these trolley inspections, the defects, if any, in the track are physically measured and prompt remedial action is taken.
Measurement of Track Parametres by Track Recording Cars (TRCs)
To make an objective assessment of the track parametres of the entire length of track, special Track recording cars, which carry special equipment to measure the track parameters on a continuous basis are run on various sections of the Railway at periodical intervals. Based on the assessment of the track parametres, prompt attention is given to the needy locations.These cars come from our centralized research organization located at Lucknow (RDSO).
Determination of Riding Quality by Oscillation Monitoring System (OMS)
To judge the riding quality of the track objectively, specially designed Oscillation Monitoring System (OMS) is fitted in nominated coaches and these special coaches are attached as the last vehicle for important Mail/Express trains and oscillations are measured on a continuous basis during the run. The system generates a list of locations of the track where oscillations exceed pre-determined values, which is used by the Maintenance Organization for prompt remedial action.