The Use Of Double Fire Shutter System In A Fire Safety Engineering Design

Protected lobbies may be stipulated by fire codes to protect openings in compartment walls. Such lobbies will in some cases impair the communication between different parts in a building. In the circumstances, the use of fire shutters may be considered. However, fire shutters available in Hong Kong's market can only provide resistance to fire in terms of integrity. As heat flux can be transmitted by radiation, such fire shutters cannot be regarded as a like-to-like substitution to protected lobbies. This paper is to demonstrate that a double fire shutter system can be an appropriate alternative means of protection to the openings against the spread of flame and heat in stead of using lobby. The effectiveness of the double shutter system will depend on the separation between the shutters and the emissivity of the shutters. Computational Fluid Dynamics (CFD) technique is adopted to analyse the influences of the two parameters. INTRODUCTION It is recognized that openings at compartment walls will defeat the fire resisting properties of the walls. However, in order to maintain good communication between different spaces in a building, provision of openings at compartment walls becomes indispensable. In accordance with paragraph 10.1 of the Code of Practice on Fire Resisting Construction, 1996, Hong Kong (FRC Code, 1996) [1], openings in compartment walls for communication of adjoining compartments should be protected by a lobby with fire resisting doors. Except for places of public entertainment or carparks, any such opening Copyright © International Association for Fire Safety Science may alternatively be protected by a fire shutter with the same Fire Resistance Period as the compartment wall with regard to the criterion of integrity. Hong Kong is a densely populated city, the land supply is scare. Multi-storey high-rise buildings are therefore constructed everywhere to satisfy the demand for various purposes. Manufacturing factories are also accommodated in multi-storey factor: buildings as if they were apartments. These multi-storey factory buildings are termed as flatted factory buildings. Raw materials, parts and goods are loaded or unloaded at the loading and unloading space situated at ground floor of the building. These goods arc then conveyed to the factories at upper floors by elevators. The loading and unloading space which is part of the carparking space and the landing areas of the elevators arc different compartments and should be separated by walls with adequate fire resistance. Any openings in such walls should be protected by lobbies. However, lobbies will obstruct the smoothness of the conveyance of the materials and goods. The FRC Code (Hong Kong) does not allow the use of a single leaf fire shutter to substitute the protected lobby. One of the reasons is that such fire shutter cannot effectively resist heat transmission. The objective of this article is to demonstrate an alternative approach by using a double fire shutter system and illustrate such double shutter arrangement can effectively resist heat transmission. It also indicates that the effectiveness of the system will be governed by the separation and emissivity of the shutters. THE PERFORMANCE REQUIREMENTS Openings in compartment walls should be protected in that flame and smoke are resisted to an acceptable standard. A protected lobby is considered to have adequate protection in that: a) it resists the spread of flame by doors with adequate fire resistance in terms of integrity; and b) it resists the spread of flame and smoke by offering a buffer zone (reservoir) for smoke and radiant heat transmission. Therefore, an alternative means of protection should also have similar resistance to spread of flame and smoke. The alternative approach by double fire shutters system is designed in which the shutters have equivalent Fire Resistance Period [FRP] as the compartment walls in terms of integrity. The arrangement is shown at Figure 1. The shutters will be operated upon actuation of smoke detectors installed immediately adjacent to the openings. If the fire shutters can function properly, the resistance of spread of flame can be regarded as adequate as the fire shutters are to provide with equal FRP as to the compartment walls in terms of integrity. The question now is whether the fire shutters can also effectively retard the smoke spread and radiant heat transmission.