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Fire safe data centre

The design requirements for the project far exceeded any fire detection and suppression project previously undertaken in South Africa. While ensuring compliance with national regulations such as SANS10139 and SANS14520, the primary design criteria was the provision of a system that would have no single point of failure and would ensure both design and construction compliance with Tier 4 standards for data centre construction.

Fire detection

A network of Ziton ZP3 analogue addressable control panels were provided to manage the fire detection and suppression equipment installed throughout the facility. The panels are interlinked using a closed loop networked configuration reporting to graphical user interface software. Due to the project design requirements referred to above, the control panels within the data centre are installed in a primary and secondary configuration, the primary panels being live, while the secondary panels are programmed to replicate the operation of the primary panel and then activated by means of a selector switch located between the panels in the event of a failure of the primary control panel.

Due to the very high air velocity anticipated within the data halls, the use of addressable point type detection was not considered as the air movements within the halls during normal working conditions would render these devices inoperable. To overcome this problem the use of ASD (aspirating smoke detection) was deemed to be the most effective solution to provide detection within the data halls.

Each data hall was fitted with a series of AirSense Micra 25 high sensitivity smoke detection units evenly distributed above the hot aisles (in the service space) and below the cold aisles within the floor void. These ASD devices were programmed to provide four levels of fire reporting.

The first three alarm levels were automatically set by the AirSense ClassiFire software algorithm which provided the most sensitive level of alarm relative to the ambient conditions within the space without the risk of false alarms whilst the fourth alarm level is adjustable at any user definable level between 1% to 25% obscuration per metre.

The Pre-alarm level (alarm one) was used to switch off the fresh air supply into the protected space and close the dampers.

The second and third alarm levels provided auxiliary fire control outputs for reporting functions only, whilst the fourth level output with fixed settings formed part of the fire suppression control facility by replicating the action of a standard point type smoke detector programmed in a typical double-knock arrangement.

Fire suppression systems

Fike Corporation’s ProInert (IG55) 300Bar systems were used throughout the facility to provide gaseous fire suppression. The majority of new inert systems installed internationally use 300Bar rated systems as this storage pressure provides up to 50% greater suppression capability than 200Bar systems currently in use in South Africa. The use of 300Bar gaseous fire suppression systems in South Africa has been extremely limited in the past due to the lack of an efficient cylinder recharging facility and a prerequisite determining the award of this project was the need to ensure such a facility was put in place prior to the system being commissioned.

The Fike ProInert Fire Extinguishing System design includes a pressure regulating valve assembly distinctly different than standard inert gas systems on the market. This design offers pipe and installation advantages resulting in overall system cost saving. It is much more sophisticated than standard decaying pressure inert gas systems. The system approach is to use a discharge valve that is designed to regulate the discharge pressure of the system to a constant 42 bar ensuring the pipe pressure and nozzle flow rates will be consistent for the duration of the discharge. Regulating the pressure at the valve outlet permits low pressure rated piping to be installed in the entire system piping network. Smaller bore piping can also be used compared to standard inert gas systems. Both features present easier system installation, reduce the pressure venting requirements and decreases the overall cost of the system installation.

ProInert has achieved system approval and product listing from several international fire approval authorities including FM, UL, LPCB etc.

Application

The design and configuration of the fire suppression systems for the data halls was developed to ensure a discharge of the fire suppression into any one data hall would not adversely affect the protection of the facility while the discharged cylinders were being refilled. To achieve this, the system design makes provision for independent ProInert fire suppression systems for each data hall. In excess of 280 x 300Bar cylinders were required per data hall and these cylinders were strategically located on custom built equipment racks located around the risk.

In the event of a first gas discharge into any of the four data halls, the cylinder banks associated with the specific data hall are used for the protection of the area. This is achieved by the activation of the solenoid controlled Master and Slave Actuators provided at each cylinder bank. The ProInert gas is then discharged into the risk area via a series of graded pipework and strategically placed nozzles located within the room space and floor void.

To provide the additional level of protection required for this high value facility, the independent fire suppression systems provided for the protection of the data halls are interconnected to each other. The flow of discharged ProInert is controlled by a series of selector valves that are electro-mechanically controlled via the programming of the associated fire control panels.

Any one data hall fire suppression systems can be directed to any of the other data halls using the control system developed specifically for this application. An example of the operation is such that in the event of a fire in any data hall resulting in the release of gas into this area and the need to remove the cylinders associated with this data hall under typical conditions the equipment within this data hall would be without fire suppression, however, the unique design of this system enables the fire control panel to automatically detect a discharge has occurred and to react accordingly.

In the event of a second fire within the same data hall, the cylinders dedicated to one of the other data halls are automatically activated and routed to the first data hall by the automatic opening of specific selector valves within the pipework reticulation system.

Approximately 50 selector valves were used in the system each controlled by a primary and secondary Master Actuator combination ensuring each valve is immediately available for re-use following a discharge.

Testing and handover

Due to the enormity of the project, it was deemed essential that both room integrity testing and full discharge testing was conducted to ensure correct operation of the system.

The volume of the largest individual risks was such that the latest room integrity systems designed and supplied by Retrotec, USA, were required to determine the level of leakage from the protected spaces, these units consist of door fan test equipment that pressurise the space and measures the pressure drop over time to determine if the fire suppression system concentration will be retained in the event of a discharge.

Following the successful room integrity testing, a controlled discharge of over 280 cylinders took place by fire simulation, Oxygen levels were measured through the protected space to ensure the design concentration was achieved and retained for the required ­holding time.

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