CO2 fire extinguisher pressure

[Guest guntherGre]

Is the CO2 gas in Co2 fire extinguishers at room temperature liquid or in gas form? We had a discussion in our company and had lots of different ideas (but no knowledge :) ). Anybody can help?

[Tom Sutton]

Since carbon dioxide is a gas at room temperature, in order for it to exist in liquid form, the gas must be stored at extremely high pressure. When the pressure is released from the extinguisher, the gas expands, cooling the air and shooting out a white cloud resembling snow. Because the gas is so pressurized, dry ice may stream from the extinguisher or form around the horn when in use. That is why you should never touch the horn it can take your skin off, nasty. :unsure:

Because it is in liquid form that is how you are able to test the contents by weight. You have the net weight stamped on the cylinder, (weight of cylinder empty) weight the cylinder with contents, the gross weight, deduct one from the other gives weight of contents. Maximum weight of contents is also stamped on the cylinder. More than 10% loss then replace or recharge, usually replace.

Read more: How Do Carbon Dioxide Fire Extinguishers Work? | eHow.com http://www.ehow.com/...l#ixzz1nrMjUx4Q

[Safelincs]

Hi

To my knowledge the CO2 extinguisher pressure at room temperature is about 55 bar, which is not enough to liquify the CO2.

But the gas has clearly got enough compression to do all the things Tom is describing with regards to cooling during expansion

Harry

[Tom Sutton]

Harry I must beg to differ check out http://en.wikibooks....ed_Correlations I accept it is a little more complicated but at NTP it is more liquid than gas.

[Safelincs]

Hi Tom

I used the CO2 phase chart

http://www.network54.com/Realm/pneuguy/co2.gif

which shows CO2 at room temperature and 55 bar to be in the gas state.

Harry

[Tom Sutton]

Cannot access the link harry

[Safelincs]

Hi Tom

Sorry, here we are (the first chart disappeared)

http://www.doomlabs.com/science/co2pv.gif

and

http://www.eng.ox.ac.uk/InvensysUTC/app2/CO2phasediagram.png/image_large

Harry

[Tom Sutton]

I will revise my first posting slightly I should have said mostly liquid in fact it is both. The bulk is liquid with a vapour layer in the ullage space providing pressure. Liquid fill is to 2/3 of the capacity of the cylinder, unless using tropical fill. The pressure will vary depending on the temperature the higher the temperature the higher the pressure and visa versa.

If you wish to research it on the internet try,

http://www.warpig.co...ynamics.shtml#2 although it is about paint balling the much of the CO2 Physics will apply to any co2 cylinder including fire extinguishers.

 

[Guest RodJack]

When a fire extinguisher valve opens the pressure inside drops and this causes instantaneous boiling in the liquid. The boiling speed is so fast that the contents as it approaches the valve is part liquid and part gas. By the time the contents is expelled out of the nozzle or horn you see a cloud of CO2 mixed with frozen water that was present in the air at the time of the discharge.

[Guest Criss]

Hi Tom

What is the standard pressure of different fire extinguisher.....??

[Tom Sutton]

As far as I am aware there is not one standard pressure for fire extinguishers, they vary depending on type, class, manufacturer and country. What I do know, when servicing, they should be treated with a great deal of respect.

[Guest neelesh]

from the link i understood it is in liquid and at top some gas phase, so what happens if the entire bottle is filled with gas???

 

[Tom Sutton]

When you are dealing with CO2 fire extinguishers the pressure is such that the gas turns to liquid and remains that way until the pressure is reduced. When it is released it turns back to a gas that is why you have a discharge horn to slow down the pace of extinguishing medium to allow it to change state and scatter the fire you are trying to extinguish.

[Guest sameer masood]

what is pressure at nozzle tip in co2 system

[Guest sameer masood]

from 55 bar it drops to what value

[Tom Sutton]

As far as I can see it depends on the temperature of the room, if you study the links above I am sure you will find the answer.