Large scale construction projects present significant challenges, and one aspect which should be considered during the early design and construction stages is adequate protection against fire risk. In subterranean and tunnel applications, selecting the right fire protection solution presents a specific challenge in terms of system design and maintenance of the installed equipment.
Examining the drivers behind the development of fire protection solutions and how these innovations can change the construction industry’s approach will help deliver greater project efficiencies and ensure the specified solution meets the required application risks.
Tunnels are a prime example of the challenges faced when designing and installing fire protection systems in large scale construction projects – complex design, installation and supply chain planning, as well as the performance requirements for these applications. As a critical part of the world’s growing infrastructure, compromises cannot be made when it comes to fire risk. The market for tunnel projects shows sustained growth, particularly in regions with infrastructure expansion plans, where road and rail tunnels are required to reach often remote or mountainous locations. Added to this, as space above ground in cities becomes ever more restricted, tunnels are considered a vital aspect of urban development. This can be seen in major tunnel projects either recently completed, or undergoing construction, with several stretching for many kilometres underground. For example, Norway, which is seen as the world leader in tunnelling, has over 900 tunnels due to its challenging terrain, including the 24.5km Laerdal Tunnel, the longest road tunnel in the world.
Drivers for innovation
Serious tunnel fires that have occurred in Europe and throughout the world have focused attention on the problems the construction industry, and fire and rescue services, face when tackling fire risk in these environments. With more traffic now passing through tunnels, the potential for accidents is increased and places greater pressure on legislative authorities, tunnel designers and operators to adapt to these evolving construction practices.
Turkey has recently announced plans for a three-storey tunnel for both road and rail use to connect the Asian and European sides of the Bosphorous river. These design innovations pose engineering challenges when it comes to ensuring that a tunnel space is adequately protected in the event of an emergency incident, such as fire or evacuation. This has led to more stringent legislation in many markets that now requires active firefighting technology alongside robust and reliable fire detection methods to prevent a fire from taking hold and spreading.
Limited access highways, road tunnels, bridges, elevated highways, depressed highways and roadways situated beneath airtight structures are covered by the NFPA 502 standard for fire protection and fire life safety. This standard establishes minimum requirements for each of the identified facilities, with appropriate measures also defined by the local authority with jurisdiction for the area. Road tunnels present a particular fire risk due to the enclosed space and access difficulties in the event of an incident. Accidents in several European tunnels, including Mont Blanc, Tauern and St. Gotthard, have resulted in tragic loss of life and highlighted the vital need for effective fire protection solutions. Developments in engineering and construction techniques are leading to longer and deeper tunnels with the aim of reducing travel time and removing traffic from some urban areas.
Designing fire protection in context
The specific features, increased traffic and enclosed space of road tunnels present a significant fire safety challenge. Aside from the primary safety concerns and damage mitigation to the tunnel structure, ongoing maintenance is a key concern, particularly given the enclosed space and resulting potential delays should the system need to discharge. Traffic flow in a tunnel environment creates a lot of dust and debris which can impact on the performance of fire protection equipment. Robust, reliable equipment designed for the required risk must also perform as specified in this enclosed area. Space is limited in tunnels, so systems that minimise installed footprint offer a major advantage to tunnel designers.
Fire protection systems must be considered as part of the overall context of the structure to engineer the system in line with other critical services, such as ventilation. Fixed fire protection systems are recommended for installation in urban tunnels carrying a variety of vehicle types, including passenger cars and heavy goods vehicles. Water-based systems offer specific benefits to tunnel operators through the ability to suppress and cool the fire, prevent fire spread, protect the overall tunnel structure and its facilities, and support essential firefighting activities.
Designing a water-based system with these considerations in mind is vital to alleviate concerns relating to reduced visibility during evacuation, hot steam and potential deflagration once the system has discharged, and the perceived high cost of installation and maintenance. Tests carried out using sprinkler systems in both the Netherlands and Japan have demonstrated that with adequate mechanical ventilation, fires can be extinguished effectively without the risk of heavy steam formation, temperature increase upstream and downstream of the fire, and deflagration. The Japanese tests in particular studied the activation time of water spray systems in order to maximise the effectiveness of the solution and minimise operator error or confusion. This led to the adoption of automatic water spray discharge systems in Japanese tunnels using an activation time of three minutes for uni-directional tunnels and 10 minutes for bi-directional tunnels.
Deluge development
Operators should look for robust, proven technology from experienced manufacturers to protect critical tunnel infrastructure. Developing new approaches to fire protection is vital in keeping up with ever changing challenges in tunnel engineering and construction. The drive for simpler, safer and more effective maintenance across a wide variety of fire protection applications has led manufacturers and distributors of fire protection products to invest in research and development to introduce increasing sophisticated solutions. Using proven and trusted technology, Tyco Fire Protection Products focuses on making these applications safer through smarter solutions that offer pure performance.
Tyco Fire Protection Products focuses on product design, performance capability and service support to drive its product development and innovation. Recognising the product performance parameters required in today’s critical infrastructure ensures products are robust and capable of withstanding these demands. Combined with technical expertise, training and knowledge, this provides operators and asset owners with the reassurance of proven performance, even in the most challenging applications.
Tyco’s DV-5 Red-E Cabinet provides a complete pre-assembled fire protection valve package. Enclosed within a free-standing cabinet that protects the valve riser, the enclosure occupies minimal floor space and prevents the ingress of dust and debris. The system is pre-wired with grooved pipe connections on the water inlet and outlet to the valve, and includes a shut-off control valve, an automatic water control valve and supervisory switches. This compact, space-saving design reduces valuable footprint and construction costs. The DV-5 Red-E Cabinet is suitable for installation directly into the tunnel wall, without the need to build a separate space. This provides a simplified solution that helps to design complexity out of the project and is easier to install and maintain. A control panel is also included in the package and can be used to make electrical connections to the power, detection, circuit and alarm units.
Combining the versatility of the DV-5 Red-E Cabinet with other Tyco components can provide optimum fire protection solutions. The TN-25 System unites the simple DV-5 with the TN-25 nozzle which is designed, tested and approved for integration into deluge water spray fire protection systems, and ideally suited for road tunnel applications.
Easy access to critical equipment can present a challenge in road tunnels, particularly when a fire protection system needs to be reset following a discharge, or for scheduled testing and maintenance. To overcome this, the DV-5 deluge valve within the Red-E Cabinet features a remote reset function that enables the product to be operated and de-activated from one or more remote locations. This removes the need for an engineer to manually re-set each valve following discharge, resulting in safer and more efficient maintenance.
The DV-5 Red-E Cabinet is designed, engineered and built at Tyco’s Centre of Excellence for valve engineering in the Netherlands, and is supplied fully assembled and tested. Not only does this make installation more cost effective, it reduces time and functionality risks associated with onsite assembly. To support fire protection specialists in the operation of its valve equipment, Tyco Fire Protection Products has introduced its advanced, innovative training tool, L.I.V.E. (Local Instructional Valve Experience). L.I.V.E is a mobile, interactive valve demonstration unit, which facilitates flexible training by Tyco experts on the company’s range of fire systems valves, including the DV-5 Deluge Valve. By sharing its extensive application knowledge and technical expertise in critical fire system equipment, Tyco is taking the lead in supporting the industry in its adoption of the most advanced and effective fire safety solutions.
Continuous innovation within the fire protection industry will enable tunnel designers and operators to be prepared to meet ever evolving challenges, legislation changes and the specific constraints and limitations of ground-breaking tunnel construction projects. Investing in proven products and total fire protection systems from a leading/accredited manufacturer helps alleviate common design and supply chain “pain points”. This approach places greater emphasis on critical fire protection, providing tunnel operators with the opportunity to minimise the need for extensive, complex retrofitting of an active fire protection system later in the project.
For more information, go to www.tfppemea.com
About the Author
Gijsbert van Rooyen is Product Manager – Valves and Devices, Tyco Fire Protection Products.
