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Posted By Raymond Rapp
As I am not familiar with this system could some enlightened sole explain the rudimentaries of the system. For example, in our vital equipment room we have C02 gas bottles, which in the event of a fire replace the oxygen in the room with CO2. However, I am concerned amongst other things that the CO2 could leak into other parts of the building undetected. Interested to find out more about this system.
Thanks.
Ray
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Posted By Ashley Wood
You do not say how many cylinders you have but my answer would be the same anyway. The system, as you rightly say, contains carbon dioxide gas and this will replace the oxygen available within the area once the system activates. If the fire has insufficient oxygen it will go out. The principle is simple but there are hazards with this type of system. Firstly, the system must be mechanically locked off at the cylinders, not just electrically isolated at the control panel. secondly, the room/area needs to have a reasonable amount of integrity otherwise the gas will escape and the concentration ratio of gas to air will not be sufficient to put the fire out.
Regarding your concern, Co2 can not be monitored by a gas sensor but oxygen depletion can. That may be a route to consider. Also, the maintenance regime should include the weighing of the cylinders as this will identify leakage.
Hope this helps.
Best regards
Ashley Wood
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Posted By Kevin Drew
Ashley,
I'm not quite sure why you think CO2 cannot be measured directly? There is an assortment of CO2 detecting equipment commercially available both portable and fixed.
Kevin Drew
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Posted By Ashley Wood
are you sure they are measuring Co2 or are they looking at oxygen reduction?
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Posted By Thomas Kennedy
Raymond
I'd speak to the manufacturer or installer. Invite them along and ask them to explain how the system works and to comment on your concerns. I'm sure they'll have had to cover these issues at the pre-sale stage.
Thomas
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Posted By Ashley Wood
Kevin, I have since looked at what you said and probably (not 100% admission)stand corrected. I was confusing N2 and Argon both of which can only be detected by oxygen reduction. However, I am not 100% convinced that it is Co2 being detected!
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Posted By Paul Oliver
Think about the fire trianlge.
reomve any one of the three meduims (Heat, Fuel, Oxygen) and you should extinguish the fire.
Co2 fills the room starving it of oxygen and so removes a fuel source.
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Posted By TBC
I think you've got the wrong end of the stick Paul - It's the possibility of the CO2 leaking into other areas that is of concern here.
A good system should not leak anyway. I've never heard of one losing enough CO2 to worry anyone. If a small amount did escape elsewhere, I don't think it would be of concern to the normal everyday levels which make up our atmosphere.
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Posted By Raymond Rapp
Thanks for your input guys. Just for the record I am pursuing other avenues with our maintenance dept. However, I am also interested in the views of my learned colleagues and you are much quicker at responding!
Incidentally, I am also concerned with not just an accidental leak of the CO2, which has been highlighted, but if the system should be operated. Above the vital equipment room is a manned control centre and I am aware that staff may be distracted by ensuring that operational exigency is maintained. Hence I need to know (amongst other things) in layman's terms how long it might take before the C02 depletes the air and becomes a human hazard? I love this job...
Cheers.
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Posted By Kevin Drew
Ray,
You probably already know this but CO2 is twice as dense as air at 2kg/m3 (at NTP). If your manned control centre is above the vital equipment room it will obviously depend on how leak tight your vital equipment room is, its dimensions, the volume of CO2 and whether or not its ventilated?
Kevin Drew
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Posted By John Donaldson
We took the opportunity a few years ago to fully discharge our 7, CO2 flooding systems which protect our HV switching and transformer bays. The CO2 bottles were all due for pressure testing.
After the discharge we monitored the atmosphere using oxygen deficiency and actual CO2 levels.
Much to our surprise we found that some of the areas took up to 45 min for the atmosphere to return to a breathable level.
Even the Fire Brigade Officers who attended some of the discharges where surprised that it took so long.
In terms of leakage we have not yet experienced any problems in the 20 or so years I have been here. (he says crossing fingers) We presently have 40 plus x 80lb bottles and at one time had over 100.
If there were to be a catastrophic leak, from the bottle, it is likely that this would active the bell and lights.
The most likely time that you might be at risk of a accidental discharge is when the pins and scotches are being put in to position when doing maintenance, as this has to be done with some care.
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Posted By David Bannister
Ray, I agree with the previous advices.
You don't say whether this is a manual system or an automatic one and what the environment is. If auto then there will be some form of fire detection equipment that then operates the release for the CO2, usually on a delay to allow controlled escape.
Surprised nobody has yet clearly said that it is ESSENTIAL that the system is locked off whilst any persons are in the protected area. CO2 in a confined space is a killer whilst being an effective fire extinguishing medium. Do not rely on the delay to get your people out.
I believe that in some marine/offshore environments this is however not practicable.
There are still thousands of these systems in use, typically in electrical switch rooms, plant rooms and the like although many have been replaced by other (safer) gaseous systems. If considering this please be aware that the existing system will become fully redundant as the pipework, nozzles etc are not compatible so expect high costs.
Maintenance is crucial, not only to ensure correct operation when needed but also to avoid incorrect, unwanted operation.
The installers/maintenance company will be able to provide you with system-specific info.
Hope this helps
David
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Posted By Colin Reeves
As a mariner I can advise that CO2 is the standard system throughout the worlds shipping (with a few other systems as well, either primary or secondary - such as hi-fog).
I have never come across automatic activation of the system owing to the high risk - it always has to be activated manually.
One other point - opening the cabinet door to release the CO2 activates the loudest alarm you will ever hear!
Colin
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Posted By Raymond Rapp
Once again many thanks for your advice.
For the record I have been deliberately vague with some facts for security reasons. Nevertheless, you have provided ample information for when I discuss the maintenance of this system with our mechanical and electrical manager. Boy, is he going to love me!
Ray
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