Maha Metro has completed flash butt welding (FBW) for the track being laid on Reach II (Sitabuldi to Automotive Square) and Reach IV (Sitabuldi to Prajapati Nagar). The organization mostly did FBW as these welds are stronger than other ones.
Rails used in Nagpur Metro Rail Project (NMRP) are generally of length 18 meter and 25 meter. The individual rails are welded together to form long-welded panels of various lengths according to alignment of track.
Rail welding is generally done by two methods:
Flash butt welding (FBW): These welds have 95% strength of its parent rails as metallurgy of rail is not changed during this process. This process is adopted for making long weld rail (LWR) panels before casting of track plinths.
Aluminum thermit welding (ATW): The process involves pouring molten iron metal between two rail panels, where a gap of 25 milimeter is left. The metal acts as glue between parent rails. This process is generally adopted to convert long weld rail (LWR) panels in to continuous weld rail (CWR) panel after track laying work is finished. These welds have 45% strength of parent rails as external material is poured between rails.
In Nagpur Metro, 18 meter and 25 meter rails have been welded to form a LWR panels of average length of 350 meter. The longest rail panel made at NMRP is of length 600 meter with twenty-four 25 meter long rails.
In Reach II and IV, total of 3,064 flash butt welds have been done to complete 100% rail panels in the month of October.
The use of ATW is only 10% of FBW in Nagpur Metro. This has been done so that the track has maximum strength.