New System Comes up Trumps for Data Centre

Unlike ordinary inert gas systems, where the discharge is controlled by a single fixed-flow restrictor that causes an initial high peak mass flow (on which the pressure relief vent area is calculated), the new Argonite C60 system uses an innovative flow control mechanism that controls the flow of gas throughout the discharge period.

This means that the peak mass flow of suppressant can be 60% lower than in ordinary systems, without compromising fire suppression performance. This reduced peak mass flow correspondingly reduces the pressure relief vent area in the protected enclosure; this significant reduction turned out to be a crucial benefit for one of the first major projects to be completed.
It is, however, far from being the only benefit. The controlled release of the suppressant gas and constant flow rate in the system means that smaller diameter pipework can be used for the delivery network. Not only is this less costly in itself, it also means that smaller holes are needed to allow the passage of the pipes into the protected enclosure, leading to further savings. Finally, the lighter weight of the pipe makes it faster and easier to install.

Further benefits stem from the system’s modular manifolds and its front-mounting actuators. The manifolds are available in four, six and eight-cylinder versions that can be combined in any required combination to meet the needs of the application, making it faster and easier to install than conventional types.

The front mounting actuators can be readily installed without the need for engineers to work at height to reach the rear of the cylinder valves. As the cylinders are approximately 3.6 metres highs, installation engineers would normally use step ladders for this task, but the C60 system negates the requirement, which means no climbing up and down and no moving of step ladders. This had a particular impact on the first major project – a high-security technical area within a data centre, comprising a room void of 5,500 cubic metres and a floor void of 1,080 cubic metres – that required 180 cylinders, resulting in a substantially reduced installation time, and the hazards that are associated with working at height.

Achieving effective fire suppression in data centres is never a straightforward task, and this particular data centre is dedicated to the handling of financial data for a major international banking client and houses over 500 data racks. Because of the sensitive and critical nature of the information, the centre had been constructed from steel-strengthened panels with internal security bars. Additionally, in order to maintain the highest possible levels of security, it was a prime requirement for the fire protection project that the penetration of these walls – necessary for venting purposes – had to be kept to a minimum. In fact, minimal wall penetration was also highly desirable from a financial point of view, as the high strength of the walls meant that normal techniques for making apertures could not be used, and the services of a costly specialist contractor were required.

Another issue that had to be taken into account was that the location of the secure area meant that it was effectively an enclosure within an enclosure, further complicating the pressure relief requirements and creating a potential need for cascade venting arrangements. The client’s consultant had also made a firm stipulation that the fire suppression system should be a clean total-flooding inert gas suppressant agent, rather than a clean chemical agent. Argonite was chosen because it has properties that are ideally suited to this application and its efficacy has been well proven in demanding data centre fire suppression installations.

Argonite is a 50/50 mixture of two atmospheric gases – argon and nitrogen – selected for their ready availability and non-toxicity, and blended to attain the same nominal density as that of air. This minimises agent leakage after discharge and ensures sufficient agent retention times and good coverage at all heights within the protected area. It is also well established as being non-corrosive, non-conducting and can be used safely in manned areas. With zero ozone depletion potential and zero global warming potential, it is an environmentally responsible choice.

As with all inert gas suppressant agents, relatively high agent concentrations are required to attain fire extinguishment. Argonite has, for example, a design concentration of 40.3vol% against Class A fires, and enclosure pressure relief is required to ensure that the pressure excursion upon system discharge remains within the enclosure’s specified pressure limit. This requirement would normally be potentially problematic in this type of application because of the wall penetration restrictions and the need for cascade venting. However, the new C60 system overcame the challenge.

With this project already well underway, there was a late change in the end user’s requirements and it became necessary to add a number of “cold aisles” to the installation within the enclosure. In essence, these are areas that receive extra cooling and, in order for this to be effective, the cold aisles are partitioned off from the other areas. This affectively creates small enclosures within the main enclosure and, while these internal enclosures presented few pressure relief problems, it was necessary to arrange for additional nozzles to be installed to ensure that the concentration of suppressant gas within the cold aisles reached design concentrations within the prescribed time.

The design calculations associated with extending the system were straightforward, confirming that, as expected, no changes were needed to the pipework other than to make provision for connecting the new extensions. Had an ordinary inert gas system been used it is likely that the work associated with this late design change would have been much more complex, and that it would almost certainly have involved replacing the upstream sections of the pipework with larger pipe sizes to accommodate the increased delivery rate.

While meeting the complex requirements of this demanding application had initially seemed challenging – in particular, satisfying the end-user’s conflicting requests for an inert gas system and for minimal penetration of the enclosure for venting – it was ultimately found that the new C60 system was an ideal solution. Not only did the controlled-flow technology used by this system greatly reduce the need for enclosure pressure relief, its other features also helped to reduce the time needed to complete the installation and the overall project costs. Additionally, when a modification was needed late in the day, the system also proved its worth in terms of flexibility and extensibility.

Contact: For further information, go to www.kfp.co.uk