Following a series of technical glitches that recently disrupted services and caused overcrowding, the Delhi Metro Rail Corporation (DMRC) has announced plans to conduct ultrasonic testing of rail welds to enhance safety and reliability across its network.

A tender issued on 7 October invites agencies to carry out Ultrasonic Flaw Detection (USFD) testing of Alumino-Thermic (AT) welds and rails using B-scan machines on six metro lines, including the Airport Express Line.

The contract, valued at around Rs 18.9 million, will be implemented over a three-year period. According to the tender, the project aims to identify hidden defects in rails and welds that could otherwise lead to operational disruptions or safety risks.

“Ultrasonic flaw detection will be deployed for rapid, non-destructive testing (NDT) of rail tracks to locate internal issues such as cracks and corrosion,” the DMRC said in the tender document.

The testing will cover Lines 3 and 4 (Blue Line) — from Noida to Dwarka and Yamuna Bank to Vaishali — which are among the network’s oldest routes and have recently experienced technical issues. It will also include Line 6 (Violet Line) from Kashmere Gate to Raja Nahar Singh, Line 8 (Magenta Line) from Janakpuri West to Botanical Garden, Line 9 (Grey Line) from Dwarka to Dhansa Bus Stand, and the Airport Express Line.

The decision follows multiple technical faults in recent months. On 1 September, the Metro recorded its third service disruption in a week, affecting the Yellow and Blue Lines, which led to severe overcrowding at several stations. A signalling fault between Barakhamba and Indraprastha and another near Millennium City Centre, Gurugram, caused trains to switch to manual operations, slowing down services.

Earlier, on 21 May, Blue Line services were delayed due to a technical issue, while on 24 August, a similar snag disrupted the Red Line.

According to DMRC, periodic ultrasonic testing is part of its preventive maintenance programme, aimed at ensuring the safety, efficiency, and reliability of one of the world’s busiest metro systems, which carries millions of passengers daily.