TPi November 2013

Grooved mechanical piping systems in tunnels At the start of the construction, tunnel- boring machinery will need to be supplied with pipework to provide clean water and compressed air, and then to remove the earth in the form of a slurry. Using the grooved method can deliver a major advantage here. Its very flexibility means that piping can be readily modified as needed and extended quickly and easily as the tunnel progresses, enhancing the construction schedule. Once built, a tunnel requires permanent services in the form of a fire main with hydrants located at intervals, which the fire service will access in the event of fire, and maybe other services such as heating,

Grooved-end pipes ready for installation and (inset) installed in the Vielha Tunnel in Spain

air conditioning and domestic water. Thermal movement is an important consideration in the design and installation of piping systems in addition to following the tunnel curvature. Designers, engineers and contractors have used grooved piping systems to address these issues in tunnels across the globe. They include the award-winning Tunnel de Fréjus between France and Italy; the Sydney Cross City Tunnel in ■ Tunnel and groove Contractors working on the 1,300m tunnel under the Vistula River in Warsaw used grooved flexible couplings to accommodate curvature and thermal movement. The project was the first in Poland to benefit from tunnel boring technology when the tunnel was constructed in 2011 to transmit water from Warsaw’s left-bank districts to the Czajka waste water treatment plant on the right bank. Two 1.6m diameter pipelines run through the 4.5m diameter tunnel that also houses the track for a service railway car, ventilation systems, closed circuit television and other installations. The Victaulic pipe joining system was selected to install the carbon steel lines for water, compressed air and slurry – safely, reliably and faster than if welding or flanging had been used. The method compressed the construction schedule and reduced the total installed cost. Because there were no hotworks or hazardous fumes associated with welding, job site health and safety was enhanced.

Australia; the Fort Smith Lake Tunnel Pipeline in Arkansas, USA; the A6B tunnel in Paris, France; the Vielha Tunnel in Spain; and the Metro Warszawskie and Vistula Tunnel in Poland. Grooved technology is currently being used in the London Underground, where Oxford Circus and Green Park stations are being retrofitted with air conditioning systems. Pipes required to transmit cooling water have to follow the curves of the existing tunnel, and safety and speed of installation are vital. The need to keep the transport network operating as normal also means there is a very limited time overnight when work can be carried out. Grooved installation is helping to raise productivity and compress the schedule: with no cumbersome welding equipment to set up or remove from the job site, installing the pipework is much more time efficient, and the flame-free joining method does not require the removal of hazardous fumes. Grooved mechanical couplings are available with two distinct performance features: rigid and flexible couplings. Rigid mechanical couplings are designed to ‘fix’ the joint in its installed position, permitting no linear or angular movement at the joints. Flexible grooved mechanical couplings, on the other hand, are designed to allow controlled linear and angular movement at each joint that can accommodate pipeline deflection and piping thermal movement. The design of the components enables grooved mechanical flexible couplings to allow for controlled movement in the pipe joint. Because the dimensions of the coupling key are narrower than the groove in the pipe, the coupling key has room to move in the pipe groove. Additionally, the width of the coupling housings allows for pipe-end separation. This leaves room for controlled linear and angular movement at the joint. The mechanical coupling remains a self-restrained joint, and the unique, pressure-responsive design provides sealing even under deflection and pipe movement. Angular deflection and linear movement

The Victaulic pipe joining system was selected to accommodate curvature and thermal movement in the tunnel under the River Vistula in Warsaw

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Tube Products International November 2013

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