August 23, 2017

Fire detection and prevention in server rooms

Fire Factors are the actual value of the equipment in a server room and the data it contains..jpg

The installation of proper fire detection and suppression systems is critical in hi-tech areas such as server rooms, in order to protect both costly equipment and valuable data in the event of any fire.

Fire detection in such a critical environment has to take into account myriad factors, from the actual value of the equipment and the data it contains, to the potential sources of ignition, which includes the presence of electricity. “More often than not it is the data and equipment you want to preserve,” ASP Fire CEO Michael van Niekerk points out.

Here a gas fire-suppression system is the best option due to the sensitivity of the equipment. “Obviously, a sprinkler or water-mist system is not really ideal due to the presence of electricity,” van Niekerk explains. “You want to ensure you are putting in a suppression medium that is not going to create more damage than the fire itself.”

In terms of gas fire-suppression systems, there are two main options. The first is to flood the server room with an inert gas such as carbon dioxide, argonite (IG-55), comprising argon (50%) and nitrogen (50%), or Inergen, a mixture of nitrogen (52%), argon (40%), and carbon dioxide (8%).

“These are high-pressure systems that flood the interior to a 60% concentration of the gas in question. The problem, of course, is that if you have human occupants still inside and they cannot escape quickly enough, they will succumb to asphyxiation,” van Niekerk warns.

Therefore a key element of any fire-suppression system for a server-room environment is that, in the event of a system discharge, any occupants receive sufficient warning to effect an escape, with a corresponding delay in the actual activation of the system itself.

Another issue that has to be taken into consideration is the potential damage that can be caused to such equipment itself by these high-pressure systems, which can operate at up to 300 bar. A related issue is damage due to thermal shock, as the equipment runs at a high temperature, and then cools down so rapidly it suffers damage in the presence of the much colder, high-pressure gas.

Van Niekerk highlights that such high-pressure systems are traditionally a third to double the price of low-pressure clean-gas systems. Here FM-200 is a popular option, a colourless, odourless gaseous halocarbon. These systems also operate at a much lower pressure of 20 to 25 bars. “Anything above 50 bar is considered to be a high-pressure system, and you actually need to be certified by the Southern Africa Compressed Gases Association (SACGA) in order to be able to work on these systems.”

FM-200 is deemed a ‘clean, safe’ gas as it leaves no residue. It is also much safer. “You can have a discharge in an occupied room, and still have five minutes to evacuate, without any ill-effects.” The main effect of the gas is that it reduces the oxygen level in the room to about 12%, from a normal 23%, which means it is too low for a fire to be sustained, while allowing humans to survive for 5 to minutes in the enclosure.

“The other benefits are that no high-pressure discharge is involved, the actual distribution of the gas in the room is far easier to achieve, and when connected with an electronic fire detection system, it eliminates false alarms,” van Niekerk elaborates.

The challenge posed by server rooms is that they often feature sunken floor voids, or a roof void with a suspended ceiling, in order to accommodate cabling. “Those volumes also need to be filled with gas, or the required concentration will not be achieved. Therefore the volume of space in a server room can be much larger than anticipated, which means that more careful planning needs to be carried out.”

One way to deal with this problem is to deploy an in-cabinet system instead, whereby the gas is simply discharged into a cabinet containing the server itself, as opposed to filling up the entire room. Here a common gas is Novec 1230, a low Global Warming Potential halon replacement. An alternative is Pyroshield, a mixture of nitrogen and argon. However, an in-cabinet system does not account for other potential ignition sources such as distribution boards or Uninterrupted Power Supply (UPS) units.

“The size of the server room in question will determine the type of solution opted for. How much equipment does it contain? Then we need to look at related issues such as whether or not the walls of the server room are fire-resistant, in order to prevent propagation of any fire to the rest of the building,” van Niekerk stresses.

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