home-made anti-fire fogging system ?

If you really think you need an installed fire extinguisher system this style might be quite good. A large SCUBA tank half full of water and then compressed air (don't know what pressure you would need but probably less than a SCUBA fill) should do the job. I imagine it might be better to buy the heat sensitive spray heads to be sure of operating temp and spray pattern. Fit a pressure switch to the system to operate an alarm if you get an activation.
I suspect however that most people fit an installed fire extinguisher system to meet specific requirements like for commercial operation. The question then becomes is your home made system regarded as meeting the requirements. good luck olewill
 
sarabande said:
with a dive bottle and a can of ordinary water, would it be possible to make up for a small boat a small scale system similar to the commercial ones ?, e.g.

http://www.marioff.com/water-mist/why-hi-fog


Needed ?

well-designed spray head, wax (?) activated sensor, dive bottle, fresh water, some pipework....
Click to expand...

Hello sarabande, I think anything suitable would work to force the water along, but the trick is in the spray head. The holes are incredibly fine, to discharge water in such small size droplets that they don't fall, but float around like a very dense fog.
I did a fire fighting course about 10 yrs ago, I am pretty sure the fog nozzle just fitted on the end of an ordinary fire hose. edit, yes, a couple of pictures on wiki.
 
Last edited:
OK, some follow-up questions...

How good are dive bottles at retaining their pressure, and what pressure do they store ?

If you fill it at the beginning of the season, will it retain full pressure till the end ?

If the compressed air is released - say -over a minute or two, are there likely to be any icing problems (as on my normal compressor tank ?




I can see the DIY approach working if people can order easily variable lengths of standard pressure hoses and couplings from e.g. garage suppliers or hydraulic pipe firms.

Leaving aside the design of the misting head, what sort of initiating system do people want ? Automatic via sensor/wax, or a manual system relying on an alarm ?
 
sarabande said:
with a dive bottle and a can of ordinary water, would it be possible to make up for a small boat a small scale system similar to the commercial ones ?, e.g.

http://www.marioff.com/water-mist/why-hi-fog


Needed ?

well-designed spray head, wax (?) activated sensor, dive bottle, fresh water, some pipework....
Click to expand...
Marioff is renowned for its unyielding commitment to innovation, with every new improvement grounded in full-scale fire tests. As the pioneer of water mist fire suppression technology, Marioff has helped establish industry standards while continuing to develop leading solutions in close cooperation with local and international regulatory authorities. Since its launch in 1991, HI-FOG® has received more than 100 type approvals as a result of thousands of full-scale fire tests. Each new installation benefits from Marioff’s deep understanding of how fire behaves and therefore offers customers the world over peace of mind.
Click to expand...
Hmmm, 'nuff said. Back to other questions:
How good are dive bottles at retaining their pressure, and what pressure do they store ? Exceptionally good 3000+ psi

If you fill it at the beginning of the season, will it retain full pressure till the end ? Oh yes

If the compressed air is released - say -over a minute or two, are there likely to be any icing problems (as on my normal compressor tank ? Not if the cylinder was filled with dry air as it should be from a properly maintained diving air compressor


As others have said the problem is not the driving mechanism rather a source for the fogging nozzles added to purity of feed water and filtering there off - even a piece of dust could block a nozzle. Commissioning of the system could present problems insofar as it would need to be spotlessly clean internally
 
sarabande said:
OK, some follow-up questions...

How good are dive bottles at retaining their pressure, and what pressure do they store ?

If you fill it at the beginning of the season, will it retain full pressure till the end ?

If the compressed air is released - say -over a minute or two, are there likely to be any icing problems (as on my normal compressor tank ?




I can see the DIY approach working if people can order easily variable lengths of standard pressure hoses and couplings from e.g. garage suppliers or hydraulic pipe firms.

Leaving aside the design of the misting head, what sort of initiating system do people want ? Automatic via sensor/wax, or a manual system relying on an alarm ?
Click to expand...

Dive cylinders are very good at retaining pressure, my cylinders are filled to 207 bar but you can get up to 300 bar cylinders now I believe.

It will retain pressure so long as your valve is in good condition.

It will probably cause icing as with releasing any high pressure air fast.

To get it filled it will also have to be in test.

:D We try to avoid water in the cylinders like the plague by filling them slowly, to prevent internal corrosion.

pete
 
pete said:
Dive cylinders are very good at retaining pressure, my cylinders are filled to 207 bar but you can get up to 300 bar cylinders now I believe.

It will retain pressure so long as your valve is in good condition.

It will probably cause icing as with releasing any high pressure air fast. it won't cause interal icing, as the air is dry. However, ice will form on the outside of the valve and associated pipe work by condensing moisture from the surrounding air. This is not going to affect the working of your proposed system.

To get it filled it will also have to be in test.

:D We try to avoid water in the cylinders like the plague by filling them slowly, to prevent internal corrosion. Breathing air compressors will fill a cylinder as fast as they can pump the air into them. The air is dried in the process of compression by going through condensers which remove virtually all the moisture from the compressed air. The condensers have to be drained periodically whilst the compressor is working: it's interesting to see how much water comes out of them, along with oil from the compressor.

pete
Click to expand...

Minor points, I know.
 
Last edited:
A dive bottle should really be kept dry. Dive compressors have multiple water traps to ensure they deliver dry air, so on an amateur, DIY basis it may be better to consider charging with CO2 or N2 - both may be available from a friendly publican as they're used to pump beer, otherwise you need to get to know some divers with access to a dive compressor to charge with dry air. CO2 is, in fact, used as extinguishers both gases being asphyxiants. To avoid corrosion in the bottle, the water would have to be stored in a seperate container, although that would not have to withstand such a high pressure. Of course, the down side of condsidering another propellant gas is that within a confined space there is a real risk of asphyxiation... just as with a commercial CO2 extinguisher. I would have thought a melting line releasing a spring to open the valve would be the easiest to manufacture.

Rob.
 
The diving cylinder will hold more than enough pressure for a very long time. The end will get sub zero C very quickly if releasing large volumes of air. As a propellant for water this would need to be carefully designed. I would not use CO2 or N2 as both would be problematic for any crew on an enclosed boat. They would certainly suppress the fire but in a large volume like that it would only take one breath to cause loss of conciousness. Air is a good bet simply to vaporise the water.
 
Water mist systems such as Marioff, sit at circa 80 bar and discharge at circa 200 bar when the pumps are running. They only pump water from a storage tanks through an atomising head. A dive bottle would provide adequate pressure but you don't want to be forcing air from a dive bottle into a fire unless you want a really big fire! You would be better not using a water mist system at all but discharging an inert gas into the fire such as Inergen, FM200 or Novec 1230. This would drop the oxygen content of the engine room or the whole boat if the system was bigger enough but it wouldn't kill you.
 
thanks geem, but the purpose is to avoid expensive, inert, non-life supporting gases or aggressive powders, in a small enclosed hull.

As I read it, the mist system reduces the temp dramatically, thus taking out one leg of the fire triangle.

I can see your concern at blasting a fire with compressed air (c20% oxygen) but misting does not seem to need rushing mighty winds to quench.

At the very early stages collecting videos and other info at present.
 
I'd say a high pressure pump would be take up less room than a dive bottle and be less of a hazard or maintenance overhead, although finding a 12 or 24vdc pump may not be straightforward; perhaps RO pumps may be of use? As mentioned, the critical part is arranging a large enough supply of clean water to squirt through it and have the system clean enough not to block itself up.
 
cliff said:
If the compressed air is released - say -over a minute or two, are there likely to be any icing problems (as on my normal compressor tank ? Not if the cylinder was filled with dry air as it should be from a properly maintained diving air compressor
Click to expand...

Yes that may well deal with internal icing but what about external icing, I have seen some pretty thick icing on 3000 psi control valves in the marine environment, enough to hinder proper operation.

Having said that I do think the idea has potential especially for engine room fires.
 
Why all the talk of eleventy-trillion bars when a fog nozzle works off normal fire hose pressure? I must be missing something as usual.
 
jerrytug said:
Why all the talk of eleventy-trillion bars when a fog nozzle works off normal fire hose pressure? I must be missing something as usual.
Click to expand...

I agree that it would at least be worth experimenting with a low pressure system. In (plant) nursery irrigation systems there are "mist" nozzles which work at 2 or 3 bar (tap pressure at very low flows) and low pressure fog (probably technically mist) nozzles which run at 4 bar and produce in the order of 100 micron droplets. These droplets won't hang in the air for very long like a true fog but it is a much much easier system to construct than "proper" high pressure fog systems. A nozzle cluster has an output of 28 litres per hour, call it 0.5 litre per minute. Let's say that you fit them on a grid of 1 m square, how many would you need in your cabin? 4 across and 5 along would be 20 = 10 lpm flow rate required at 4.0 bar. There are a few little diaphragm pumps which would do that no problem or you could maybe use a pre-charged pressure vessel. (where the water is contained in a bladder and only the air is in contact with the inside metal of the vessel. You would need a clean water supply and very fine filter. The trouble with irrigation kit is that it all is plastic so nbg as far as fire is concerned. Pipes could be very small as the flow rates are so low so copper maybe? Making your own nozzles would be an interesting challenge though there might be something suitable out there. Actually you are probably going to need more nozzles - more water -more flow than that but I reckon it would be do-able as long as you have space in your boat somewhere to put a few bits and pieces.
These are the ones I am familiar with: http://www.naandanjain.com/uploads/...ges from NDJ_micro_eng_121113_F-11_Fogger.pdf

You do have to have pipe and nozzles everywhere! I couldn't do it in my boat as the nozzles would have to be made in teak or monogamy to be in keeping :) bit of a shame really given the flaring Taylors cooker, oil lamps and well seasoned oil soaked kindling everywhere you look.
 
I imagined that a SCUBA tank half filled with water and then pressurised to 3000psi would be used. You would need to use an Ali tank to avoid rust.
This would be piped at 3000PSI to a spray head with a wax seal that would melt wiith heat. Or use a manual valve. I would imagine the water would be expelled over perhaps 1 minute. No air would be expelled until the water was emptied. There would be a pressure drop of half or a doubling of the air volume over 1 minute which I don't think would cause significant cooling as to ice the system. anyway just a thought olewill
 
William_H said:
I imagined that a SCUBA tank half filled with water and then pressurised to 3000psi would be used. You would need to use an Ali tank to avoid rust.
This would be piped at 3000PSI to a spray head with a wax seal that would melt wiith heat. Or use a manual valve. I would imagine the water would be expelled over perhaps 1 minute. No air would be expelled until the water was emptied. There would be a pressure drop of half or a doubling of the air volume over 1 minute which I don't think would cause significant cooling as to ice the system. anyway just a thought olewill
Click to expand...

It would be interesting to know how much more effective a super fine high pressure fog would be compared with a low pressure fog. The droplets would be smaller so evaporate more quickly but conversley there would be less water. Reliability would be more of an issue with the (even) smaller nozzles needed on a very high pressure system.
 
The water mist systems installed commercially use typically 12mm s/s pipework with a system pressure when pumps are running of over 200 bar. The pumps are identical to watermaker pumps (triple piston pumps). The pressure is this high to create the water mist. it isn't a spray. The mist is so fine you can discharge into a running engine room and not damage electrical equipment. It is widely used in data centres as the discharge will not trash expensive computer servers. unless you operate at these kind of pressures you will not create a mist, you will have a sprinkler system where you need lots more water and you will damage your electrical equipment, possibly. The manufacturers of water mist do not run at these pressures accidentally. it is done for good reason. Having installed these systems in data centres I would say that unless you have a very large yacht these systems will not be viable. You would be better off with a bottled gas system which work very well in small confined engine rooms typically found on yachts.
 
You must log in or register to reply here.

Share this page

Top