Design operations are in demand at Fläkt Woods UK after winning its largest ever single contract, the project worth more than €7 million is to supply ventilation fans for the massive Marmaray tunnel rail project in Turkey.
The contract will supply the air movement needs on one of the world’s biggest transportation infrastructure schemes, the 13.6 kilometres (8.5 mi) Bosphorus crossing. It has been described as the project of the century, and the tunnel will connect two continents with the €1.9bn rail-tunnel running deep beneath the Bosphorus Straits.
The tunnel consists of a series of earthquake-proofed immersed tubes, assembled from 11 sections, each as long as 130 metres and weighing up to 18,000 tons. These will be placed down to 60 metres below sea level; making it will be the world's deepest undersea immersed tunnel tube.
The Colchester Company is supplying a range from their super-powerful Axial fans for eight shafts ventilating the new crossing. Measuring up to 2.8 metres in diameter, the fans will be capable of providing emergency ventilation in the worst-case scenario – a fire on a freight train more than a kilometre long.
The specialist fans generate a relatively high velocity discharge of air-flow through the tunnel. As the jet from the fan diffuses, it transfers energy to the tunnel airflow and creates an increase in static pressure, which causes air to flow as in any conventional system.
Paul Wenden, the Company’s engineering and marketing director, said: “We export half of what the Colchester factory produces, and our ability to diversify, sourcing business in both the building and infrastructure and industry markets, has helped us to find new business and this contract is a great example of this.”
Additional underground stations will be constructed at 3 locations, and 37 new above-ground stations will be rebuilt or refurbished. Once it is operational, the new transport link is likely to attract more than 1.5 million passengers using the tunnel per day.
The Company is tasked with the successful management of the contract, as Phillip Walker, Fläkt Woods' Project Management Leader explains “The design of these state-of-the-art industrial fans utilised Computational Fluid Dynamic analyses and Finite Element Analysis, at the beginning of the design process, which has helped to prove their ability to withstand high temperatures and the challenging operating conditions associated with both high pressure and pressure pulses. Fläkt Woods is tasked with planning, documenting, organising, securing and managing the tunnel ventilation equipment supply to bring about the successful completion of all the contract’s goals and objectives.”
To achieve the duty requirements within the Fläkt Woods Design team had to develop a product dedicated to this application. Due to the high pressure the fan must be a two stage fan, and due to the space constraint the two impellers will be fitted on the same motor shaft. The fans are also designed to be 100% reversible so that supply fans can also extract. To clear smoke from one side of a fire, reversible fans may be used with the duct system to create a longitudinal flow along the tunnel. The requirement to clear smoke in the event of a fire has resulted in a need for the fans to operate at elevated temperature.
The tunnel designers have established that the fans will need to operate at up to 300°C for up to two hours during a fire to keep escape routes clear long enough for people trapped underground to escape. Given the safety-critical role of the fans, as part of the contract a fan will be third-party tested and certified to prove that they can operate at 300°C for two hours.
A significant proportion of fans from the Company’s range are used in tunnel and metro application, with a more demanding requirement to operate at up to 400°C for up to two hours is becoming increasingly common. This requirement is driven by tunnel and metro design engineers, who are increasingly finding that overall tunnel ventilation system design, can be better optimised for both routine day operation and emergency operation in the event of a fire, if the fans are capable of operating at 400°C. Tunnel designers for the Marmaray project were able to optimise the ventilation system design around fans capable of operation at 300°C.
Tunnel and Metro design engineers are raising the standard for fire safety, and consequently tunnel ventilation fans increasingly have to operate at higher temperatures. Historically tunnel ventilation fans were designed with no elevated temperature capability, however now it is a legal requirement within Europe for tunnel ventilation fans to comply with EN 12101-3, the Euro Norm that sets out how fan intended for application in tunnel ventilation systems must be third-part tested and certified. The Euro Norm EN 12101-3 has been converted into an international standard, ISO 21927-3 providing a basis for tunnel ventilation fans to be certified outside Europe. Fläkt Woods has been active in developing tunnel ventilation fans that are approved in accordance with the requirements of EN 12101-3 at both 300°C and 400°C and has a policy of offering fans certified in accordance with ISO 21927-3 outside Europe.
For more information email info.tunnels@flaktwoods.com
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