Kasara Ghat, Maharashtra
2023
The Hindu Hrudaysamrat Balasaheb Thackeray Maharashtra Samruddhi Mahamarg is one of Maharashtra’s major infrastructure projects. Package 14 includes twin-tube road tunnels extending approximately 7.7 to 8 km through the hydrogeologically challenging and eco-sensitive Kasara Ghat terrain in the Western Ghats.The tunnel fire protection system incorporates a high-pressure water mist network designed to provide effective fire suppression while significantly reducing water consumption compared with conventional deluge systems.
Operating at hydraulic pressures of up to 140 bar, the system uses stainless-steel tubing and specialised high-pressure components to distribute water mist throughout the tunnel. For such a large underground installation, conventional welded tubing presented challenges related to hot-work safety, material integrity, post-weld treatment and installation time. PreFiS® non-welded press-fit tubing technology provided an alternative cold-connection method, eliminating welding at the tubing joints while enabling rapid installation of the high-pressure stainless-steel network.
Installing a high-pressure water mist network across an extensive tunnel presents a unique combination of pressure, safety, accessibility and installation challenges. The system operates between approximately 60 and 140 bar, requiring reliable tubing connections capable of maintaining integrity under high hydraulic pressure. At the same time, the tunnel environment creates additional challenges for conventional welding.
The project therefore required a connection technology that could combine: High-pressure integrity + material preservation + installation speed + reduced hot work
To address these challenges, PreFiS® non-welded cold-press technology was used for the high-pressure tubing system. Unlike conventional welding, PreFiS® creates the connection through controlled mechanical deformation. A high-integrity metal sleeve is positioned over the tube ends and permanently compressed using a calibrated hydraulic press tool, creating a metal-to-metal mechanical seal without applying heat to the tubing.
This provided four key advantages for the tunnel application.
The Samruddhi Mahamarg tunnel project demonstrates how PreFiS® non-welded tubing technology can be applied to high-pressure fire suppression infrastructure in a demanding underground environment. With the system operating at pressures of up to 140 bar across approximately 8 km of tunnel infrastructure, the project required a tubing connection method capable of delivering reliable hydraulic performance while addressing the practical challenges of underground installation. By replacing conventional welded connections with cold-press PreFiS® fittings, the installation approach eliminated hot work at the tubing joints, avoided welding-related heat exposure and significantly reduced connection time. The project analysis estimates a 25–35% reduction in total installed cost, attributed to factors including reduced NDT requirements, elimination of hot-work ventilation overheads and shorter installation timeline
The project demonstrates the potential of non-welded tubing technology for large-scale underground fluid systems. By combining cold-press installation, high-pressure capability and stainless-steel tubing, PreFiS® provides an alternative to conventional welding where installation safety, material integrity and project speed are critical. The project documentation identifies the resulting system as a reliable and hydraulically optimised fire suppression network, with the non-welded approach enabling rapid installation while avoiding welding-related heat exposure.
Implemented PreFiS® non-welded tubing technology
Samruddhi Mahamarg – Package 14
Twin-tube tunnel through Kasara Ghat
Approximately 8 km tunnel infrastructure
High-pressure water mist fire suppression system
Operating pressure up to 140 bar
316L stainless-steel tubing
Cold-press mechanical connections
No welding at tubing joints
Reduced hot-work requirements
Smooth internal bore profile
2–5 minute connection time
Installation timeline compressed by more than 60%
Estimated 25–35% reduction in total installed cost
Application in a challenging underground environment
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