Weld failure is a common cause of derailment; corrosion a threat to health of tracks
With the life span of railway tracks coming down sharply over the years due to increasing passenger-freight operations, higher axle loads on dense traffic routes and corrosion, Southern Railway has set a rail renewal target of 72 kilometres this fiscal as a key component of its measures to maintain safety.
Going by standard estimates, a 60-kg rail segment with a traffic density projection of 800 Gross Million Tonnes (GMT) is about 15 years, but this conventional calculus is being constantly revised, as many rail segments are coming up for renewal in less than half that time, Railway officials said.
With a route length of 5,000 kilometres, Southern Railway is the fifth largest rail network among the 17 zonal railways in Indian Railways network. It runs about 434 suburban trains and 742 non-suburban trains and transports around 2.4 million passengers on an average every day. On the freight front, the originating freight loading from April to July this year was 14.81 million tonnes, the 14 per cent increase over last year being the best-ever loading for the first four months of any year in Southern Railway’s recorded history.
“The upkeep of the vast rail network involves a well-drawn out daily, monthly and periodic maintenance schedule involving men and machines,” said S. Anantharaman, Chief Safety Officer, Southern Railway.
For instance, a track recording car to detect defects, twists or faulty alignment is deployed once every four months in Grade A segments (based on a set of wear-and-tear parameters), once in six months for Grade B sections and once a year for other segments. The data is analysed to arrive at a Track Geometry Index (TGI) value that determines the course of action.
Ultrasonic Flaw Detectors (USFD) to spot weld failures, Oscillation Monitoring Systems to measure vertical and lateral displacement from a normal axis of coaches moving across a particular rail section and tight tamping to bind together caked up ballast are also part of standard procedure, officials said.
Apart from machines, the Railways also deploys gangmen and keymen to physically inspect every bit of the 5,000-km route length.
In the four months of this fiscal, yard derailments have halved from 22 in the same period last year, while mainline accidents dropped from eight to just one.
One of the most common causes for derailments is weld failure. In-house studies in the Railways estimate that rail and weld failures currently account for over 60 per cent of engineering-related mishaps - a sharp rise from the 25 per cent about four years ago.
Commissioner of Railway Safety S. K. Mittal’s preliminary report on the derailment of Muzaffarpur-Yesvantpur Express near Arakkonam on April 10 too has upheld rail weld failure as the cause of the accident that killed one person.
The other significant threat to the health of tracks is coming from corrosion due to exposure to coastal atmosphere or contact with toilet waste. It is estimated that corrosion causes fracture of an estimated 20 per cent of rail lines.
“The Chennai-Gudur and Chennai-Villupuram lines are among the worst affected lines due to corrosion,” said a track engineering official.
Though the Railways has started using corrosion-resistant alloy-rails to beat the problem, the proportion of these rail segments is minuscule with regard to the magnitude of the problem.