The SABS has approved and is legislating the adoption of ISO 14520 as the clean agent gas extinguishing standard in South Africa. In this issue, we continue our comprehensive look at this standard.
Pipe and valve supports
Pipe and valve supports shall be suitable for the expected temperature and shall be able to withstand the dynamic and static forces involved. Due allowance shall be made for the stresses induced in the pipework by temperature variations. Adequate environmental protection shall be given to supports and associated steelwork.
Adequate support shall be provided for nozzles and their reactive forces such that in no case shall the distance from the last support be greater than as follows:
* <25 mm pipe <100 mm
* >25 mm pipe <250 mm
Movement of pipework caused by temperature fluctuations arising from environment or the discharge of extinguishant may be considerable particularly over long lengths and should be considered in the support fixing methods. Sling-type support should not be used.
Valves
All valves, gaskets, O-rings, sealant and other valve components shall be constructed of materials that are compatible with the extinguishant and shall be suitable for the envisaged pressures and temperatures. Valves shall be protected against mechanical, chemical or other damage. Special corrosion-resistant materials or coatings shall be used in severely corrosive atmospheres.
Nozzles
Nozzle choice and location
Nozzles, including directly attached to containers, shall be approved and shall be located with the geometry of the enclosure taken into consideration.
The type number and placement of nozzles shall be such that:
* The design concentration is achieved in all parts of the enclosure.
* The discharge does not unduly splash flammable liquids or create dust clouds that might extend the fire, create an explosion or otherwise adversely affect the occupants.
* The velocity of discharge does not adversely affect the enclosure or its contents.
Where clogging by foreign materials is possible, the discharge nozzles shall be provided with frangible discs or blow-out caps. These devices shall provide an unobstructed opening upon system operation and shall be designed and arranged so they will not injure personnel.
Nozzles shall be suitable for the intended use and shall be approved for discharge characteristics, including area coverage and height limitations.
Nozzles shall be of adequate strength for use with the expected working pressures, they shall be able to resist nominal mechanical abuse and shall be constructed to withstand expected temperatures without deformation. Furthermore, nozzle discharge orifice inserts shall be of corrosion-resistant material.
Nozzles in ceiling tiles
In order to minimise the possibility of lifting or displacement of lightweight ceiling tiles, precautions shall be taken to securely anchor tiles for a minimum distance of 1,5 m from each discharge nozzle. Discharge nozzles shall be permanently marked to identify the manufacturer and size of the orifice.
In addition, the inlet of any nozzle assembly or pressure-reducing assembly which contains an orifice of area less than 7 mm2 shall be provided with an internal filter capable of preventing obstruction of the orifice.
Detection, actuation and control systems
Detection, actuation and control systems may be either automatic or manual. Where they are automatic, provision shall also be made for manual operation. Such systems shall be installed, tested and maintained in accordance with appropriate national standards. Unless otherwise specified in a national standard, 24 h minimum standby sources of energy shall be used to provide for operation of the detection, signalling, control and actuation requirements of the system.
Automatic detection
Automatic detection shall be by any method or device and shall be capable of early detection and indication of heat, flame, smoke, combustible vapours, or any abnormal condition in the hazard that is likely to produce fire.
For further details contact the FDIA on tel: (011) 397 1618.
Due to its length, Hi-Tech Security Solutions will now publish the Gas Extinguishing Standard over 8 parts and not 5, as was reported earlier.
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