Joint expansion due to tremendous heat can lead to failure of standard firestop measures.
Hilti rises to challenge of a tall order
Hilti’s CP 672 solution, specially developed for curtain-wall applications, is among a wide range of firestop products that Hilti has provided to protect Burj Dubai.
01 March 2009
AN ARRAY of Hilti firestop products has been used to provide passive fire protection to the world’s tallest tower, the Burj Dubai.
Among the many products used on this 800-m-plus tower, is the tested and approved firestop solution Hilti CP 672 speed spray, which has been especially developed for curtain-wall applications where maximum movement is required, says its manufacturer the Liechtenstein-based Hilti Corporation.
“The Burj Dubai is protected against flames, smoke and gases in places most people could only imagine,” says Karel Ludvik, Firestop product manager at the Hilti Regional Office for the Middle East and South Asia region. “The seams between the building’s outer shell and the individual floors will be sealed in such a way that temperature and wind-related warping of the building’s hung façade can be compensated for. The joints are generally 152 cm wide and are first closed off with compressed rockwool. Then Hilti CP 672 firestop joint spray, delivered to the construction site in 19-litre buckets, is applied.”
Hilti CP 672 consists of a latex spray-applied coating, which can accommodate 15 per cent joint width movement in a fire.
Detailing the system and its application at Burj Dubai, Ludvik says: “This convenient and sprayable system, which has a very good consistency, ensures fast installation while saving labour and time. The worker applying the spray must pay close attention to ensure that the coating extends about 12 mm beyond the actual joint to cover the floor as well as the same length vertically along the façade.
“When the spray dries, and shrinks slightly, it leaves a membrane that adheres to both construction surfaces. The membrane and rockwool would resist a fire on the lower floor, delaying its spread to the floor above and thus providing valuable time for the evacuation of people. Hilti CP 672’s acrylate coating reacts with great elasticity in such situations, expanding to cover any increase in the joint that would be generated by the façade warping outwardly because of a fire’s extreme heat. Traditional fire prevention solutions would fail in this case.
“The coating also inhibits penetration by smoke, making it extremely difficult for smoke and gases – the main cause of death in fires – to rise. The coating also allows little air penetration, has sound insulating properties and is resistant to water, mildew and aging.”
The Burj Dubai makes extensive use of Hilti Firestop products. Besides the CP 672, the tower also features Hilti’s firestop joint filler that seals wall-to-wall and wall-to-floor joints, as well as Hilti FS-one intumescent firestop sealant for sealing cable and pipe penetrations.
“These innovations, as small as they may seem in light of the massive tower, can save lives and material goods in case of an accident,” Ludvik stresses.
Turning to fire safety issues in the regional market, Ludvik indicates that the issue of fire-resistant curtain-wall constructions is not adequately addressed, primarily due to the perceived additional costs involved.
“In reality, the installed cost differential is not high compared to the high-performance curtain-wall systems being installed on many prestigious projects,” he points out.
He emphasises that fire-resistant glazing should form a part of a fire-risk strategy in a building: “It should be used to provide compartmentation at critical points in the building layout and a strategy should be chosen to match the building’s characteristics and needs. For example, this could be on every other floor or on every third floor if that suits the needs of the overall fire protection objectives.
“Internal, re-entrant corners and external escape stairs would be perfect situations for fire-resistant glazing in the façade as would glazing adjacent to flat roofs, external escape ways and key connections between different areas of the building,” he explains.
Elaborating on the role of firestop systems in curtain-walls, he says: “Traditional firestop systems comprise of mineral wool pads, friction fitted between floor slab and curtain-walling. A curtain wall is subject to positive and negative wind loads as well as occupational live loads and the firestop products must compress and recover over a series of these cycles without a gap opening up. They are also required to accommodate sheer movement. In a fire, the deformation of the curtain-wall can lead to firestop products falling out of the gap. In tests using real office furniture, flashover through failure of the curtain-wall occurred within six minutes.”
Hilti firestop products provide superior passive fire prevention performance, while also meeting increasingly demanding local requirements. Hilti’s solutions are comprehensively tested to ensure compliance with regulations and legislation, he adds.
Service
With more than 20 years of experience worldwide, Hilti is one of the leading suppliers of firestop systems. The company says it helps customers manage their firestop projects better by providing quick engineering judgments; extensive technical literature; on-site training and demonstration; sophisticated jobsite logistics; and assurance of conformity with specific application requirements.
The company also has an international network of firestop specialists as well a local network of experienced sales representatives, field engineers, firestop specialists and customer service representatives.
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