BS en 12845-2004 Fixed Firefighting Systems — Automatic Sprinkler Systems — Design, Installation and CRACK

EN 12845:2004 (E)

Annex E

(normative) Special requirements for high rise systems

E.1 General The requirements q of this annex shall be applied pp to the sprinkler p protection p of multi-storey buildings with a height difference between the highest and lowest sprinkler exceeding 45 m. The requirements are applicable to buildings intended for use with occupancies where the hazard is classified as no greater than OH3. Special fire engineering solutions are needed for high rise systems with hazards greater than OH3, and specialist advice should be sought.

E.2 Design criteria E.2.1 Hazard group High rise sprinkler systems shall comply with the requirements for Ordinary Hazard Group III protection. E.2.2 Subdivision of high rise sprinkler systems High rise sprinkler systems shall be sub-divided into sprinkler installations such that the height difference between the highest and lowest sprinkler on any one installation does not exceed 45 m (see Figures E.1 and E.2). E.2.3 Standing water pressures at non-return and alarm valves The minimum standing gp pressure at any y non-return or alarm valve inlet shall be no less than 1,25 times the static head difference between the valve and the highest sprinkler on the installation. Non-return valves controlling installation flow shall operate correctly with a ratio of service pressure to installation pressure not exceeding 1,16:1, as measured by valve lift and pressure equalization upstream of the non-return valve. E.2.4 Calculation of distribution pipework for pre-calculated systems The main distribution pipes, including risers and drops, between the highest design point in an installation and the zone subsidiary stop valve at the same floor level shall be sized by hydraulic calculations. The maximum friction loss shall not exceed 0,5 bar at a flow of 1000 l/min (see 13.3.4.2). Where sprinkler protection is at various floor levels in an installation, the allowable pressure loss between the design points and zone subsidiary stop valves on lower levels may be increased by an amount equal to the difference in static head gain between the sprinklers at the level concerned and the highest sprinkler in the installation. 149

EN 12845:2004 (E) E.2.5 Water pressures Pipework, fittings, valves and other equipment shall be capable of withstanding the maximum pressure likely to be encountered. To overcome the problem of pressures in excess of 12 bar, hydraulic alarm gongs may be driven via a pressure reducing valve or from a secondary water supply such as a town main, controlled by a diaphragm valve connected to the main installation control valve alarm port.

E.3 Water supplies E.3.1 Types of water supplies The system shall have at least one superior single water supply. E.3.2 Pressure and flow requirements for pre-calculated installations. The water supply shall be designed to achieve a minimum pressure and flow condition at the zone subsidiary stop valve outlet as specified in Table 6, taking Ps to be the pressure difference equivalent to the height of the highest sprinkler above the installation zone subsidiary stop valve. E.3.3 Water supply characteristics for pre-calculated installations. The water supply characteristics shall be determined by a hydraulic calculation of the pipework upstream of the zone subsidiary stop valve outlet, at the higher and lower flow rates specified in Table 6, and shall include calculations at the water supply datum point. E.3.4 Pump performance for pre-calculated installations. Automatic pumps shall have characteristics in accordance with Table 16. NOTE Pressures are taken at the pump outlet or the relevant stage of multi-stage pumps, on the delivery side of any orifice plate.

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EN 12845:2004 (E)

Key 1 Storage tank 2 Multistage pump 3 Flow meter 4 Water supply datum point 5 Alarm valve station (with bypass arrangement)

6 Flow test and zone drainage 7 Zone subsidiary stop valve 8 Water flow alarm switch 9 Sprinkler head 10 Water flow alarm switch rest valve and zone drain valve

Figure E.1 — Typical layout of high rise system with pump supply 151

EN 12845:2004 (E)

_< 45 m

1

_< 45 m

1

10 7 6

8

9

5 4

3 6 2

Key 1 Storage tank 2 Multistage pump 3 Flow meter 4 Water supply datum point 5 Alarm valve station (with bypass arrangement)

6 Flow test and zone drainage 7 Zone subsidiary stop valve 8 Water flow alarm switch 9 Sprinkler head 10 Water flow alarm switch rest valve and zone drain valve

Figure E.2 — Typical layout of high rise system with gravity tanks and booster pumps

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