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DiData goes with gas

The Dimension Data campus, covering 75000 m², is located north of Johannesburg in Bryanston and contains administrative offices, Telkom patch rooms, a network operations centre, IT workshops and equipment rooms. The protected area is approximately 3000 m³ and accommodates racks upon racks of servers. This excludes the approximately 65 Telkom patch rooms. The total building area is 20 000 m² and houses telephone equipment, DC power and battery storage, rectifiers, UPS room and AC switchgear.

A suitable solution

One of the significant challenges that DiData faced when deciding on a gas extinguishing system for these critical areas was finding an economic, environmentally friendly, people safe system that could be designed and maintained by locally available experts. The product eventually chosen was Pyroshield, which is manufactured by Alien Systems & Technologies.

"Fire suppression in these critical areas is a key concern. We required a solution that would allow us to employ earliest intervention without harm to the sensitive electronic equipment," says Nick Shaw of DiData.

In addition to the design and supply of the 10 tons of gas extinguishing equipment, Alien Systems & Technologies was also contracted to perform a comprehensive room integrity testing evaluation.

Design method and highlights

The Pyroshield system was designed and installed in a purpose-built storeroom with pipe routing to the protected areas. One of the advantages of Pyroshield is the small floor area required for cylinder storage. This together with the superior flow characteristics of inert gas agents allows longer pipe runs and smaller diameter pipes than the halocarbon agents. This maximises real estate value in terms of useable floor area and allows cylinders to be grouped in a central storage area.

The system design was carried out in co-operation with the architects and civil engineers. During the design phase it became apparent that with such a large gas extinguishing system, room over pressurisation would become significant. Initial calculations to predict enclosure pressurisation revealed that venting would be required. Due to the unique architectural style of the building, a novel solution was found, utilising the ceiling void and service ducts and passages to allow excess pressure to be vented through special grills which form an architectural feature of the front of the building.

In order to validate the over pressurisation calculations, which were carried out on Alien System & Technologies' specialist VdS design software, room integrity testing was utilised.

Room integrity testing is now a mandatory requirement for fire suppression systems in South Africa, regardless of the type of extinguishant.

Normally, the integrity tester creates a positive pressure within an enclosure and measures the return air in order to calculate the leakage factor and hold time, the minimum hold time at the design concentration being 10 minutes, this test is known as an ELA test.

However, in larger gas extinguishing systems where ceiling leakage is a factor or in the DiData campus configuration where the ceiling volume is used as a vent plenum, the ELA test is inaccurate.

In order to provide accurate results, both room and ceiling voids were pressurised utilising two sets of pressurising equipment, this allows ceiling leakage to be determined accurately and is known as a BCLA test.

State of the art enclosure modelling software is then utilised to determine the achieved concentration, ELA, BCLA and hold times, which are typically 20 minutes for Pyroshield.

Comprehensive flow engineering of the piping system was also carried out, together with coordinated engineering of the various pipe routes with Alien Systems & Technologies working in close association with the installation contractor, Joda's Electrical & Fire.

Not only does the Pyroshield system have full international approvals (Bureau Veritas) but the local manufacturer, Alien Systems & Technologies, has an ISO 9001 accreditation by British Standards for designing, manufacturing and supplying gas extinguishing systems.

The client was therefore able to install a system that complied with local and international standards, is backed up by competent local engineers and is the most cost effective total flooding system in South Africa: the product is not linked to the USD/EUR/GBP exchange rates.

An additional benefit is that the cost of system refills (as is the case with halocarbon gasses, which can be as much as 85% of the system installed cost) is not exchange rate sensitive, and of course Pyroshield will never be phased out due to environmental concerns, as is already happening with the halocarbon gasses under the Kyoto and Montreal protocols.

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