No pressure gauge on CO2 extinguishers

[Guest RobDur]

All our fire extinguishers are inspected and serviced annually. We carry out monthly in-house inspection and some of our Fire Wardens keep recording the missing gauge on CO2 Fire extinguishers. Must this pressure gauge be fitted on all of them please?
Thank you very much for your advice!

Kind regards
Robert

[Safelincs]

Hi Robet

CO2 extinguishers do not require gauges, so there is no point for the fire wardens to point this out.

Harry

[green-foam]

I would suggest that if your fire wardens record the fact that CO2 extinguishers have "missing" pressure gauges, you need new fire wardens. If they are getting  it worng about this, what else are they getting wrong?

[AnthonyB]

CO2 extinguishers don't have gauges as they self pressurise (by the boil off of liquid CO2 into CO2 gas in the ullage space) as oppose to being separately pressurised by a Nitrogen over gas and as a result remain at constant pressure until all the liquid CO2 has gone, so a gauge wouldn't tell you anything!

Also cartridge operated water, foam & powder extinguishers have no gauge as they are under no pressure until actuated.

[Guest Chetan Patle]

On 27/08/2015 at 10:01 PM, AnthonyB said:

CO2 extinguishers don't have gauges as they self pressurise (by the boil off of liquid CO2 into CO2 gas in the ullage space) as oppose to being separately pressurised by a Nitrogen over gas and as a result remain at constant pressure until all the liquid CO2 has gone, so a gauge wouldn't tell you anything!

Also cartridge operated water, foam & powder extinguishers have no gauge as they are under no pressure until actuated.

Hi Anthony, could you please explain this in simple terms.

I'll appreciate your response.

Thanks,

[green-foam]

My understanding is:

When a CO2 Extinguisher is initially filled, it is done so with a specific amount of CO2 (depending on size of extinguisher)

As the CO2 is under considerable pressure, most of it turns into a liquid inside the cylinder.

The amount of liquid is NOT enough to fill the whole cylinder (its not meant to)

As there is a "space" above the liquefied CO2 the CO2 "boils" turns into CO2 gas and fills this space at pressure.

If there was a gauge fitted on the extinguisher (Like other stored pressure extinguishers) it would always show "full" since any CO2 in the extinguisher will "boil off" and fill the space, so giving the appearance of being full when it isn't. The easiest way to check a CO2 extinguisher is to weigh it and compare these weights to what is stamped on the body of the extinguisher.

 

A "pressurised at use / cartridge" extinguisher (Like the one below)

has no gauge because there is no pressure until its release mechanism is operated, at which time a CO2 cartridge is punctured, releasing CO2  which in-turn forces out the contents of the extinguisher. (Water in the case of the one shown above)

[AnthonyB]

It's as the above states - If you want to eliminate the science what happens is a CO2 extinguisher maintains an almost constant pressure until there is no more liquid CO2 in the cylinder (when it's just about empty), so even if a pressure gauge was fitted it would still show full even if the extinguisher is almost empty.

[Guest Amber]

We have the foam & dry powder cartridge extinguisher which has a gauge however the gauge is always in the red zone. The service provider is saying that the gauge will show empty as it is cartridge operated. While I understand this however why would the manufacturer provide the pressure gauge if it is supposed to be in 0

[Guest guest 25]

Ok you need to get professionals in straight away, cartridge extinguishers don't have gauges & a gauge should never be in the red, you need a new service provider & new fire wardens.

[AnthonyB]

I'd second that, your service provider obviously has no clue about extinguishers and is ripping you off. Cartridge extinguishers are rare these days and have no gauge. Correct servicing of these each year involves (amongst other things) opening them up, replacing the O rings to the neck, removing and weighing the cartridge, examining the interior of the body (removing the contents as required to do so) checking the spindle and valve, blowing the diptube and hose to check for obstruction.

Stored pressure extinguishers have gauges and cannot be opened up for annual inspection and are check weighed and the gauge tested for free movement using a special tool and the hose removed and blown to check for obstruction and the o ring replaced (amongst other things).

If the gauges are in the red then, even if still full of foam or powder the pressuring nitrogen has leaked off (either due to partial use and even less than a second of discharge can lead to this; or through wear and tear of the spindle o-ring; or generally a faulty valve; or rust leading to pinhole rupture) and this THEY WILL NOT WORK!

Get them replaced along with the cowboys who are 'servicing' your equipment.