Guidance Note Additional Requirements for Watermist Systems Protecting High-rise Buildings
Additional Requirements for Watermist Systems Protecting High-rise Buildings SCOPE... 3 DESIGN PARAMETERS... 3 SUBDIVISION INTO ZONES... 3 HYDRAULIC PIPEWORK CALCULATION... 3 WATER SUPPLIES... 4 POWER SUPPLIES... 4 ADDITIONAL CONSIDERATIONS... 4 REFERENCE DOCUMENTS... 4 2 of 5
SCOPE This document sets the additional requirements for automatic water mist systems, for buildings in which the height difference between the highest and lowest water mist nozzles exceeds 45m. These apply to buildings falling under the fire hazard classification as detailed within BS EN 12845:2015 for ordinary hazard occupancy groups OH1 to OH3 (identified in table A.2). It is noted that these supplemental requirements are in addition to those defined within BS 8489 series or an equivalent recognised watermist standard. DESIGN PARAMETERS Assumed maximum areas of operation High-rise buildings shall be designed taking into account an assumed maximum area of operation (AMAO) of at least 216m². Note: VdS has advised on the design for high-rise buildings following the proven European OH1 design flux density, but using the OH3 (216m 2 ) dimensioning area. The new VdS water mist standard VdS 3188en will take the same approach. This is because from the fire hazard categorization perspective the fire load equals to OH1 definitions, but due to significant building height the required safety can be achieved by using 216m 2 dimensioning area. SUBDIVISION INTO ZONES The area covered by automatic water mist nozzles to be controlled by any zone valve set shall have the following restrictions: a) Similar to conventional sprinkler systems, water mist systems should be subdivided into zones, with a maximum of 200 automatic nozzles per zone or a plan area of 2400m 2, whichever is the lesser. b) The building shall be water mist-protected throughout* 1. c) The water mist zone should cover no more than one floor level, which may however d) include a mezzanine floor no greater than 100m 2. e) Car parks and areas involving the unloading and storage of goods should be covered by separate un-zoned systems* 1. HYDRAULIC PIPEWORK CALCULATION System piping shall be fully hydraulically designed taking into consideration the entire piping system to deliver the required water flow and pressure to the AMAO. 3 of 5
WATER SUPPLIES The system must have at least a single water supply with enhanced availability Single water supplies with enhanced availability are to be regarded as superior because of their higher degree of reliability. These include the following: a) Public water supply system with one or more pump modules, which is fed from two sides, each side is able to satisfy the pressure and flow rate requirements of the building; it has to be supplied by two or more water sources and may not be dependent on a single main water supply. The pump system must include at least one additional pump module as redundancy. b) Reservoirs which can hold the entire amount of water required. c) The pump system must include at least one additional pump module. d) The use of a booster pump is not allowed. POWER SUPPLIES The power supply must be provided from two independent sources. These can be the following: a) Public networks. b) Own power generation. c) Diesel engines. d) Back-up power generators. ADDITIONAL CONSIDERATIONS Watermist protection of high rise buildings should be done in consultation with the stakeholders including AHJ, F&RS and insurers and address any special considerations (such as combustible external cladding, and any fire strategy for the premises). Notes *1 Test data must be available to support watermist use for all hazard categories identified within the building. REFERENCE DOCUMENTS For further guidance please refer to the below publications. BS EN 12845:2015 Fixed firefighting systems automatic sprinkler systems design, installation and maintenance VdS 3188en VdS Guidelines for Water Mist Sprinkler Systems and Water Mist Extinguishing Systems (High Pressure Systems), Planning and Installation. 4 of 5
DISCLAIMER The information set out in this document is believed to be correct in the light of information currently available but it is not guaranteed and neither the Fire Industry Association nor its officers can accept any responsibility in respect of the contents or any events arising from use of the information contained within this document. Tudor House, Kingsway Business Park, Oldfield Road, Hampton, Middlesex TW12 2HD Tel: +44 (0)20 3166 5002 www.fia.uk.com 5 of 5