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Extinguishing water pipeline of ductile cast iron in the new Swiss Galgenbuck tunnel

Ductile iron pipe systems have proved their worth for extinguishing water pipelines in road tunnels for decades now and in case of fire events they are extremely reliable for delivering firefighting water. After the opening of the A4 bypass in August 1996 there was a steady and enormous change in the traffic flow in the Schaffhausen and Neuhausen am Rheinfall region, resulting in an enormous increase in the traffic load on the feeder routes. In 2007, the Council of the Canton of Schaffhausen presented the implementation project for the new two-lane Galgenbuck tunnel which, as a bypass route, should almost halve the traffic load in the district of Neuhausen am Rheinfall and make the Schaffhausen South junction viable in the long term.

Valves made of ductile cast iron

The route of the tunnel – Source: Bundesamt für Straßen (ASTRA), Switzerland

New construction project for traffic relief

Meanwhile the new Galgenbuck tunnel passes under the municipality of Neuhausen am Rheinfall in a wide arc, the two-lane road in the tunnel runs for a total length of 1,138 m with a maximum gradient of 4.5 % from the “Engi” portal in the West to the “Bahntal” portal in the East close to the Schaffhausen South motorway junction. The completion of all work and its commissioning is scheduled for the end of 2019.


An extinguishing ductile cast iron water pipeline in the service duct

With the ongoing installation of the operating and safety equipment, the extinguishing water pipeline with its lateral outlets to the hydrant recesses at road level is the first thing to be installed in the service duct (WELK) located beneath the carriageway. Following that will be the installations for monitoring and controlling the tunnel. The pressurised water pipeline in the service duct consists of ductile iron pipes of the vonRoll ECOPUR type in nominal size DN 250. It runs for a total length of 1,060 m in alignment with the tunnel with a minimum curve radius of 500 m and is fixed to the concrete back wall and the floor of the service duct by pipe clamps. The changes of direction in the curve are accommodated by the deflectability of the push-in joints.

From the main pipeline in the service duct, lateral branch pipelines spaced a maximum distance of 150 m apart supply the seven hydrants in the road space with extinguishing water. The branch pipelines are also constructed of ECOPUR full-protection DN 125 pipes in ductile cast iron and they run through a casing pipe above a chamber lying approximately 3 m below the hard shoulder to the hydrant connections. For the installation, overhaul and maintenance of the fire hydrants, the hydrant chamber is accessible at any time via an 80 x 80 cm large entrance from the road space.

The full-protection vonRoll ECOPUR pipes are integrally coated with polyurethane (PUR) and are classified in accordance with standard EN 545 as cast iron pipes with reinforced coating for use in all ambient conditions. Because of their highly resistant, pore-free PUR coating to EN 15189 they can be used in all types of soils and therefore have the best protection against corrosion even in the aggressive climate of the tunnel. ECOPUR pipes have a polyurethane (PUR) lining in accordance with EN 15655, that minimises deposits and, because of extremely low friction losses, promotes the hydraulic performance of the extinguishing water pipeline in case of fire. The entire pressurised water pipeline including the hydrant branch pipelines is secured against longitudinal forces by the assembly-friendly vonRoll HYDROTIGHT thrust protection system. The flexible cast iron pipe system is completed by vonRoll ECOFIT full-protection fittings with push-in and flanged joints which are also integrally protected the with a thick epoxy coating to EN 14901 and the enhanced requirements according to RAL-GZ 662.

Valves made of ductile cast iron

Schematic cross-section of the Galgenbuck tunnel – Source: Bundesamt für Straßen (ASTRA), Switzerland

High-performance hydrants for extinguishing water supply

The hydrant recesses are equipped with the high-performance double-armed vonRoll HYPLUS type hydrants which can deliver a maximum output of 4,000 l per minute (at a differential pressure of 1 bar). The patented joints between the top and bottom parts of the hydrants allow stepless 360° directing of the hydrants in the narrow installation recesses. The flexible VARIO 2.0 type H2L hydrant bottom with a maximum adjustment range of 70 cm (in 5 cm increments) offers optimal flexibility in the hydrant chambers when bridging over the existing level differences. The DUO maintenance shut-off installed as standard allows later overhaul work on the hydrant under full system pressure without decommissioning the extinguishing water supply.


Full-protection valves for secure operation and simple maintenance

At the high point of the tunnel vonRoll VS 5000 type shut-off valves are used as pipeline valves and for cleaning purposes. At the same time a vonRoll vent valve is arranged at this point to extract air from the extinguishing water pipeline. The extinguishing water pipeline in the service duct is equipped with a VS 5000 pipeline valve at each hydrant branch pipeline for uncomplicated inspection.

Author: Roger Saner, vonRoll hydro (suisse) ag

The article was slightly shortened by the editors. You can find the complete article with various illustrations as a PDF in the download area under Downloads Annual Issues EADIPS FGR.