Gas extinguishing standard: Part 6

November 2001 Fire & Safety

Part 1: May 2001


Part 2: June 2001


Part 3: July 2001


Part 4: September 2001


Part 5: October 2001


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.

Extinguishant

General

This clause sets out the requirements for the specifications, system flow calculations and extinguishant concentrations.

Specification, plans and approvals

Specifications

Specifications for gaseous fire-extinguishing systems shall be prepared under the supervision of a person fully experienced in the design of gaseous extinguishing systems and, where appropriate, with the advice of the authority. The specifications shall include all pertinent items necessary for the proper design of the system such as the designation of the authority, variances from the standard to be permitted by the authority, design criteria, system sequence of operations, the type and extent of the acceptance testing to be performed after installation of the system and owner training requirements. Extinguishant specifications are included in the various parts of ISO 14520 for the specific agent (ie Parts 2-15).

Working documents

Layout and system proposal documents shall be submitted for approval to the authority before installation or modification begins. The type of documentation required is specified below. Deviation from these documents shall require permission from the authority.

* Drawings, to an indicated scale of extinguishant distribution system, including containers, location of containers, piping and nozzles (any valves and pressure-reducing devices) and pipe hanger spacing.

* Name of owner and occupant.

* Location of building in which hazard is located.

* Location and construction of protected enclosure walls and partitions.

* Enclosure cross-section, full height or schematic diagram, including raised access floor and suspended ceiling.

* Type of extinguishant being used.

* Extinguishing or inerting concentration, design concentration and maximum concentration.

* Description of occupancies and hazards to be protected against.

* Specification of containers used, including capacity, storage pressure and mass including extinguishant.

* Description of nozzle(s), including inlet size, orifice port configuration, and orifice size/code and orifice size of pressure-reducing devices, if applicable.

* Description of pipes, valves and fittings used, including material specifications, grade and pressure rating.

* Equipment schedule or bill of materials for each piece of equipment or device, showing device name, manufacturer, model or part number, quantity and description.

* Isometric view of extinguishant distribution system, showing the length and diameter of each pipe segment and node reference numbers relating to the flow calculations.

* Enclosure pressurisation and venting calculations.

* Description of fire detection, actuation and control systems.

System flow calculations

General

System flow calculations shall be carried out at a nominal extinguishant storage temperature of 200°C, shall have been validated by an accredited approval authority by appropriate tests as described in ISO 14520, and shall be properly identified. The system design shall be within the manufacturer's specified limitations.

Balanced and unbalanced system

A balanced system shall be one in which:

* Each actual or equivalent pipe length from the container to each nozzle are all within 10% of each other;

* The discharge rate of each nozzle is equal.

Any system that does not meet these criteria shall be considered to be an unbalanced system.

Friction losses

Allowance shall be made for the friction losses in pipes and in container valves, dip tubes, flexible connectors, selector valves, time delay devices and other equipment within the flow line.

Pressure drop

The pressure drop shall be calculated using two-phase flow equations for liquified gases and single-phase flow equations for nonliquified gases.

Valves and fittings

Valves and fittings shall be rated for resistance coefficient or equivalent length in terms of pipe, or tubing sizes with which they will be used. The equivalent length of the cylinder valves shall be listed and shall include syphon tube (where fitted), valve, discharge head and flexible connector.

Piping length

The piping length and nozzles and fitting orientation shall be in accordance with the manufacturer's approved manual to ensure proper system performance.

Drawings

If the final installation varies from the prepared drawings and calculations, new as-installed drawings and calculations shall be prepared.

Liquified gases: specific requirements

Allowance shall be made for changes in elevation as specified in the relevant section of that part of ISO 14520 relating to the specific extinguishant. The minimum discharge rate for liquified extinguishants shall be sufficient to maintain the velocity required for turbulent flow to prevent separation.

Enclosures

The protected enclosure shall have sufficient structural strength and integrity to contain the extinguishant discharge. Venting shall be provided to prevent excessive over or under-pressurisation of the enclosure.

To prevent loss of extinguishant through openings to adjacent hazards or work areas, openings shall be permanently sealed or equipped with automatic closures. Where reasonable confinement of extinguishants is not practicable, protection shall be extended to include the adjacent connected hazards or work areas.

Forced-air ventilating systems shall be shut down or closed automatically where their continued operation would adversely affect the performance of the fire-extinguishing system or result in propagation of the fire. Ventilation systems necessary to ensure safety are not required to be shut down upon system activation. An extended extinguishant discharge shall be provided to maintain the design concentration for the required duration of protection. The volumes of both ventilation system ductworks shall be considered as part of the total hazard volume when determining extinguishant quantities.

All services within the protected enclosure (eg fuel and power supplied, heating appliances, paint spraying) that are likely to impair the performance of the extinguishing system should be shut down prior to, or simultaneously with, the discharge of the extinguishant.

To be continued in the next issue.

For further details contact the FDIA on tel: (011) 397 1618.





Share this article:
Share via emailShare via LinkedInPrint this page



Further reading:

Carrier rebranded Kidde Global Solutions
News & Events Fire & Safety
From July 2025, the former Carrier Fire & Security South Africa will operate under its new name, Kidde Fire & Security South Africa, as part of the global realignment of the commercial and residential fire and security business.

Read more...
Hotel enhances guest safety and aesthetics
Fire & Safety
Hotel Montresor Tower, a stylish four-star destination just outside Verona, Italy, has successfully upgraded its fire detection infrastructure with Hochiki's advanced Latitude life safety platform.

Read more...
Directory of suppliers
Technews Publishing SMART Security Solutions Fire & Safety
The Directory of Product and Solution Suppliers for the fire safety industry includes details of companies that provide security and risk mitigation products, advice, and services within this market.

Read more...
Detect fires in the early stages
Securiton Products & Solutions Fire & Safety
The SecuriSmoke range from Securiton offers various levels of coverage and power to suit every budget and application. What all the models have in common is that they can detect smoke in very small quantities.

Read more...
SecuriHeat ADW linear heat detector
Securiton Products & Solutions Fire & Safety
The SecuriHeat ADW linear heat detector uses sealed tubes positioned over the detection area, and a remotely positioned control unit detects pressure changes in the tubes brought about by changing temperature.

Read more...
Fire safety in commercial kitchens
Technews Publishing Kestrel Distribution Products & Solutions Fire & Safety Commercial (Industry)
Fire safety in commercial kitchens is becoming increasingly critical. Defender is Europe’s first EN 17446:2021-approved kitchen hood fire suppression system and offers the indispensable safety measures required.

Read more...
The crucial role of fire, smoke, and gas detectors
Fire & Safety Facilities & Building Management
From wireless detectors to integrated building management systems, the industry is seeing a significant shift towards more intelligent, more responsive solutions. ASP Fire CEO Michael van Niekerk shares insights into these innovations.

Read more...
South African fire standards in a nutshell
Fire & Safety Editor's Choice Training & Education
The importance of compliant fire detection systems and proper fire protection cannot be overstated, especially for businesses. Statistics reveal that 44% of businesses fail to reopen after a fire.

Read more...
Secutel maintains ISO certifications
News & Events Fire & Safety
Secutel Technologies has successfully recertified all four of its ISO standards, a reflection of its continued commitment to excellence, client trust, and operational integrity.

Read more...
Protecting solar panel installations
Technoswitch Fire Detection & Suppression Products & Solutions Fire & Safety
Vulcan Integrated Solutions partnered with Technoswitch and installed Protectowire’s Confirmed Temperature Initiation (CTI) Series Linear Heat Detection (LHD) system, specifically designed for harsh environments, to offer fire protection for solar panels.

Read more...










While every effort has been made to ensure the accuracy of the information contained herein, the publisher and its agents cannot be held responsible for any errors contained, or any loss incurred as a result. Articles published do not necessarily reflect the views of the publishers. The editor reserves the right to alter or cut copy. Articles submitted are deemed to have been cleared for publication. Advertisements and company contact details are published as provided by the advertiser. Technews Publishing (Pty) Ltd cannot be held responsible for the accuracy or veracity of supplied material.




© Technews Publishing (Pty) Ltd. | All Rights Reserved.