20km
4000+
350+ m/day
<8 weeks
The fire suppression network had to be installed throughout the tunnel while meeting demanding pressure and safety requirements. Every connection had to provide dependable pressure integrity because the completed pipeline feeds the tunnel’s high-pressure Fire Mist System.
A traditional welded installation would have introduced several challenges
To overcome the limitations of conventional welding, Cenergy Offshore used PYPLOK® non-welded compression fittings for the high-pressure stainless-steel tubing network.
The PYPLOK® cold-swage process uses portable hydraulic tooling to compress the fitting directly onto the tubing, creating a permanent mechanical seal without heat or purging and without the post-installation NDT requirements associated with welded joints described in the case study.
1. Preparation
The stainless-steel tube is cut, deburred and marked to establish the required insertion depth.
2. Positioning
The PYPLOK® fitting is positioned onto the tube up to the marked depth.
3. Swaging
A portable hydraulic tool compresses the fitting onto the tubing to create the joint.
4. Inspection
The completed connection is immediately verified using a Go/No-Go gauge.
This simplified workflow enabled trained operatives to complete and verify connections in minutes while avoiding the specialised welding certification, hot-work permits and post-installation radiography associated with the conventional approach described in the case study.
The 22 mm stainless-steel piping was installed along the tunnel ceilings and walls using scissor lifts, articulated boom lifts and mobile scaffolding platforms.
Because the hydraulic tooling was portable, installation crews could move efficiently along the tunnel and continue work across the full installation length without the infrastructure and preparation associated with welding operations.
This combination of cold-swage joining technology and mobile field deployment allowed the project team to maintain a high installation velocity throughout the tunnel.
The project team successfully installed approximately 20 km of 22 mm stainless-steel tubing, incorporating around 4,000 PYPLOK® fittings, at a sustained installation rate of more than 350 metres per day. The complete high-pressure fire suppression network was built, inspected and commissioned in less than eight weeks, while successfully passing a 180-bar hydrostatic pressure test to validate its readiness for 120-bar operating pressure.
In July 2026, a vehicle fire occurred inside the Dwarka Expressway Tunnel, generating thick smoke and trapping nearby motorists. The tunnel’s automated fire detection system responded by activating the high-pressure water mist system, which rapidly discharged water mist to provide localised cooling and contain the fire before emergency crews arrived.
During the incident, the installed high-pressure piping network was subjected to the resulting hydraulic pressure event. The PYPLOK® fittings maintained their structural seal integrity, with no joint failure reported.
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The incident provided a valuable real-world validation of the piping system’s performance under actual fire-response conditions, demonstrating that the non-welded PYPLOK® connections maintained their integrity while the fire suppression system was operating under pressure. This performance reinforces the reliability of the installed network for critical tunnel fire protection applications.
The Dwarka Expressway Tunnel project demonstrates that joining technology can be a critical factor in project delivery.
For large-scale infrastructure projects where installation speed, safety, pressure integrity and commissioning schedules must all be managed simultaneously, the choice between welded and non-welded piping systems can fundamentally influence project execution.
Cenergy Offshore’s execution of the Dwarka Tunnel fire suppression piping network demonstrates how cold-swage technology can enable rapid, reliable installation of high-pressure piping in demanding infrastructure environments.
Steel Plant Shutdown reduction by 60 Hrs
Steel Plant Shutdown reduction by 60 Hrs
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