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.
Operating devices
Automatic operation
Electrically operated fire detection systems shall comply with either BS6266 or BS5839. The electric power supply shall be independent of the supply for the hazard area, and shall include an emergency secondary power supply with automatic changeover in case the primary supply fails.
When two or more detectors are used, such as those for detecting smoke or flame, it is preferable for the system to operate only after signals from two detectors have been received.
Manual operation
Provision shall be made for manual operation of the firefighting system by means of a control situated outside the protected space or adjacent to the main exit from the space.
In addition to any means of automatic operation, the system shall be provided with the following:
a) One or more means, remote from the containers, of manual operation;
b) A manual device for providing direct mechanical actuation of the system; or
c) An electrical manual release system in which the control equipment monitors for abnormal conditions in the power supply and provides a signal when the power source is inadequate.
Manual operation shall cause simultaneous operation of the appropriate automatically operated valves for extinguishant release and distribution.
The manual operation device shall incorporate a double action or other safety device to restrict accidental operation. The device shall be provided with a means of preventing operation during maintenance of the system.
Note: The choice of the means of operation will depend upon the nature of the hazard to be protected. Automatic fire detection and alarm equipment will normally be provided on a manual system to indicate the presence of a fire.
Control equipment
Electric control equipment
Electric control equipment shall be used to supervise the detecting circuits, manual and automatic releasing circuits, signalling circuits, electrical actuating devices and associated wiring and, when required, cause actuation. The control equipment shall be capable of operation with the number and type of actuating devices utilised.
Pneumatic control equipment
Where pneumatic control equipment is used, the lines shall be protected against crimping and mechanical damage. Where installations could be exposed to conditions that could lead to loss of integrity of the pneumatic lines, special precautions shall be taken to ensure that no loss of integrity will occur.
Operating alarms and indicators
Alarms or indicators, or both, shall be used to indicate the operation of the system, hazards to personnel, or failure of any supervised device. The type (audible, visual or olfactory), number and location of the devices shall be such that their purpose is satisfactorily accomplished. The extent and type of alarms or indicator equipment, or both shall be approved.
Audible and visual pre-discharge alarms shall be provided within the protected area to give positive warning of impending discharge. The operation of the warning devices shall be continued after extinguishant discharge, until positive action has been taken to acknowledge the alarm and process with appropriate action.
Alarm indicating failure of supervised devices or equipment shall give prompt and positive indication of any failure and shall be distinct from alarms indicating operation or hazardous conditions.
Hold switches
Hold switches, where provided, shall be located within the protected area and shall be located near the means of egress for the area. The hold switch shall be a type that requires constant manual force to inhibit system operation. Operation of the hold function shall result in both audible and distinct visual indication of system impairment. Operation of the hold switch when the system is in the quiescent state shall result in a fault indication at the control unit. The hold switch shall be clearly recognisable for the purpose intended.
To be continued in the next issue, Part 6: November 2001.
For further details contact the FDIA on tel: (011) 397 1618.
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