Fire detection & suppression for emergency generator room

[vp1959]

Could you please advice the appropriate fire detection and suppression system for emergency generator room?
The generator room located in the basement is having 5x 1,700kVA emergency generators and engine room mounted emergency switchboard and control system arranged to start and load as per the power demand.
The room is provided with 10 supply fans, each rated for 40,000 CFM and protected with heat detectors rated for 57deg.C and automatic suppression system using form water sprinkler, reported to be approved by the local authorities.
As the generators are operated on 75% load before insulating the exhaust silencers, the detectors operated the suppression system arranged for total flooding. This spraying water above the running generators caused the generator to trip and inoperative as the winding/ panels became wet.
My questions are:
a) Is form sprinkler system suitable for generator room, especially total flooding on multiple emergency generator room?
b) Is 57Deg.C heat detector suitable, noting that summer ambient in this area cross above 50deg.C? In case the supply fans are stopped during the generators running on load or generators stopped without cooling down, the temperature will shoot above 57deg.C and activate the suppression system
c) What is the best suppression system and detections system as per IEC or BS?
Appreciate your feedback

 

[MikeHalloran]

Maybe it's time to insulate the silencers.


Mike Halloran
Pembroke Pines, FL, USA

 

[vp1959]

Already insulated

 

[wayne440]

57C = about 135F. I claim no expertise in fire sprinkler systems, but that seems pretty low for a generator room. To me, spraying water on a generator seems wrong, unless as a last resort to prevent loss of the entire facility.

The chance that a sudden shutdown of fans or the sets themselves could trigger the system is a disaster in the making. A situation like that is bad enough (say your fuel supply runs out) without adding a flood to the misery.

 

[MikeHalloran]

Depending on where you are, standards and local requirements of which we are not aware may govern.

Speaking just from what little common sense I have retained:

CO2 or other inert gas system might make more sense in a generator room. Water in any form doesn't usually get along with generators.

Having all of the generators in one room gives you a single point of failure, as you have already demonstrated. Is it possible that someone designed the system to operate properly with insulated silencers, so that your test was outside the prescribed envelope?

I can see a foam system making sense to protect the building from individual generator fires, but that sort of assumes partitions between the generators, and individual foam emitters, not just 'fill the room with foam'.

On the other hand, if we assume the building is on fire first, from causes other than a generator fire, or even so, I would want the generators to run, even while they burn. So I might not want a fire suppression system at all. I think NFPA makes a distinction between 'standby' generators and 'emergency' generators.

Perhaps the situation would become more clear if we knew the answer to this question: How did it come to be your problem?




Mike Halloran
Pembroke Pines, FL, USA

 

[vp1959]

I am the one supplied the generators and customer provided the room
Location is Kuwait

 

[SteveWag]

Get rid of the temperature operated heads. Go to a smoke detector operated system; use at least two detectors, maybe three before releasing any fire suppressant. Maybe use a dry pipe system. Use ODP style generators and supply shields or drip covers over all electrical equipment. You need to fight fire, not heat. If the cooling fans quit, spraying water is not the cure.
Steve

 

[ScottyUK]

Direct optical flame detection is another possible solution. Smoke detection in a 400,000 cfm airstream would permit a decent size fire to establish before the detector picked it up.

ODP machines are a maintenance nightmare in a location like Kuwait because of the dust. TEFC designs dominate the smaller sizes, and TEAAC or TEWAC dominate the medium-sized market.

 

[WTRVS]

Maybe you should consider the use of a "hi-fog" sprinkler system. This is a high pressure sprinkler system that does not flood the entire room with water but it creates a tight water mist. With a few liters of water under high pressure, you can put out a fire in no time. Even electrical components can survive this. In the link below you can find an example of an engine onboard a cruise ship that caught fire after a fuel leak. The fire was under control in 35 seconds and with a reasonable water quantity.

As Mike already told, there are also some inert gasses that can be used. There is a gas called "Halon" that was very good as extinguisher but then the use of this product was forbidden because "it can harm the ozone layer when released". I've heard that they now want to allow it again because it was the best gas to put out a fire. As a replacement for Halon there is also "Novec" wich is now used on ships for example. This contains argon and nitrogen and it allows personnel to escape when being exposed to this gas. When using Co2, it can be dangerous when somebody is still out there.


More details:

http://www.touchbriefings.com/pdf/1195/Marioff_tech.pdf

Hi-fog system in auxilary engine room:

http://www.youtube.com/watch?v=9O-wI7lLego

Kind regards,

WTRVS

 

[MikeHalloran]

More about Halon and replacements:

http://www.linkedin.com/groups/Clea..._most_recent_rich-0-b-ttl&goback=.gmr_3958425

Mike Halloran
Pembroke Pines, FL, USA

 

[EEJaime]

vp1959,

As others have already stated heat detectors in a generator room are a mis-application of technology. Even a higher temperature head, (210 degF here in the States), would not be recommended. Smoke detection also does not work well because with the heat and air movement and less than clean environment, the smoke sampling chambers become fouled quickly and the detectors become unreliable.

ScottyUK's suggestion of direct optical flame detectors has also worked for us in the past

The currently used replacement that we use in lieu of the Halon fire suppression system is FM-200 by Dupont.

http://www2.dupont.com/FE/en_US/products/FM200.html

It should be available in most areas. I think that's the same product that MikeHalloran referred you to. We often put these systems in as "pre-action" systems wherein they don't automatically release the agent until a certain time-delay-after-alarm, to allow personell to confirm that it is required as a discharge and re-charge of the agent is expensive. There is an "abort" push button in the control room in case of a false alarm.

The Hi-Fog systems are just starting to come into use here, and we have just had a few approved by our AHJ in the past few months.

Good Luck with your project.

EEJaime