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Specifiers Journal 2016

Specifiers Journal 2016

Putting a stop to fire

Putting a stop to fire Fire-stopping is perhaps one of the least understood but most commonly installed elements of all passive fire protection systems. ASFP CEO Wilf Butcher explains why its correct installation is vital. The concept of fire compartmentation is simple. It aims to keep fire, smoke and noxious gases to a restricted area by dividing a building into fire resisting compartments. So when installing a passive fire protection system, it is important to understand the potential implications of incorrect installation. When a building is designed there are regulations and codes of practice governing the size of compartments within the building. Each wall, floor and ceiling will have a fire resistance requirement i.e. a period of time for which it must ‘resist’ a fully developed fire. These periods generally range from ½ hour to 4 hours depending on the usage of the premises, the size and location of the compartment and the presence of other protection systems. Good example of fire-stopping cables & pipes The construction of the walls, floors and ceilings will be carried out in accordance with these design criteria. But in order for any building to be usable, openings will have to be made for doors, windows, mechanical, electrical services and expansion joints, etc. It is these breaches that need to be addressed through the installation of fire-stopping. There are many proprietory fire-stopping products available that are designed to seal compartment breaches and fill construction joints, thereby reinstating the fire resistance of the wall, floor or ceiling to its original state. These need not only provide a barrier to fire, but also need to accommodate the possibility of services burning away and leaving holes in the compartment. A good example is a soil pipe passing through a wall. These are generally 110mm plastic pipes. Just sealing around these pipes will be inadequate because the fire will cause the pipe to melt and burn away very quickly, leaving a large hole for the fire and smoke to pass through. One solution to this is a pipe collar that is fitted around the pipe and fixed to the wall or floor. Pipe collars are fitted around the pipe and fixed to the wall and floor (Rockwool) Inside the pipe collar is an intumescent material that, when exposed to heat will expand and exert pressure on the plastic as it softens, eventually crushing the pipe before the flame and smoke can pass through the wall or floor. While the primary purpose of fire-stopping is to reinstate breaches in compartment walls and floors, it is also important to remember that they serve other functions as well. If you want to block an opening to stop a flame going though, the easiest way would be to bolt a steel plate over the hole. However, although this would stop the flame, the 54 SPECIFIERS JOURNAL

heat transmission through the steel would lead to materials combusting on the non-fire side of the wall or floor and the fire would spread into the next compartment. Consequently, the fire resistance of separating elements is expressed in minutes of Integrity (preventing the passage of flames and hot gases) and Insulation (limiting the temperature rise on the unexposed face). If a product has a claimed fire resistance of 60 minutes, the end-user should be satisfied that it satisfies both Integrity and Insulation for this period. Fire test evidence Compartmentation is a simple strategy that can have a major effect on improving life safety and reducing property losses. But reading the installation instructions is only part of the story, it is important to ensure that the product specified is suitable for the intended application. Check the product’s fire test and other evidence to ensure it adequately supports the end use application for which it is being used. Similarly, never mix products from one manufacturer with those of another manufacturer. If such products have not been tested together they may not work. See ASFP Advisory Note No.6: Mixing and matching components. Installation best practice In many applications firestopping products have to accommodate movement of the services or joints in every day usage. Sealants used around hot water pipes, or chiller pipes, can be subject to expansion, or contraction of the pipework that will produce both tensile and shear loads on the product. If the product is incapable of Penetrating services should be supported either side of the compartment wall by fire-tested supports (Hilti) In many applications fire-stopping products have to accommodate movement (Siderise) meeting this criteria it is likely that it will fail when exposed to fire. Similarly, the gap between the slab edge and a curtain wall construction will be subject to movement of the curtain wall façade due to positive and negative wind loads. Any fire-stopping product used in this application should be able to demonstrate its ability to recover its shape through testing. Facade movement must be accommodated by a flexible seal that must be adhered or mechanically fixed to the slab according to the manufacturer’s guidelines. See ASFP Advisory Note No. 7: Horizontal linear joint seals. In all applications, penetrating services should be supported either side of the compartment wall by fire-tested supports to prevent collapse of the seal in a fire. The distance to the first support is particularly important and manufacturer’s instructions should be followed. In the absence of information, the first support should be no more than 300mm from the face of the seal. See ASFP Advisory Note No.8: Issues surrounding service support centres. Fire and smoke protection measures are also necessary within air conditioning and ventilation systems. These are Fire dampers are fitted where non-fire resisting ductwork passes through fire compartment walls (Rockwool) SPECIFIERS JOURNAL 55

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