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Fire Extinguishers and Co2 and solenoids.


Fish Fanatic
Aug 4, 2023
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East Yorkshire
Sorry mods. Posted this in the wrong thread... new and just finding my way around.
Kia Ora.
Hi all. I'm a marine electrical engineer, and certificated Marine Engineer, with 40 years of experience.
I've read through threads about FE (Fire Extinguisher) as a source of Co2. There are some failures out there so I wanted to share my experiences with pneumatics and solenoids which I have probably worked on hundreds of.

"Carbon dioxide is obtained as a by-product during the industrial manufacture of ammonia, alcohol and fertilizers. The gas is captured, purified and compressed in a multi-step process, and finally liquefied. Liquid carbon dioxide is stored and transported in pressurised tanks at a low temperature."

There is also food grade Co2. This is refined to a greater extent. But most of us I'm sure will be using industrial Co2. As found in FE's and bottles from Co2 suppliers, unless you go out of your way to find food grade Co2. Quite difficult but not impossible as pubs and bars use it in their beers. This is the best if you can get it.... "food grade".
A solenoid is basically a electro magnet which when energised generates a magnetic field to pull the plunger (or armature) up. This pushes against what is typically a rubber seal against the pressure of a spring. This opens the solenoid. When the power is switched off the de-energised armature (plunger) is pushed back down by the spring to close the rubber diaphragm.

Tip;- Over a long period of time the spring gets tired and can no longer generate the pressure to close the valve or seal. The springs are finely tuned to provide just enough pressure but not so much the electromagnet has to work too hard to open the solenoid. This would cause the solenoid coil to overheat and fail, burn out.

Now industrial Co2 tanks are not coated as well as food grade tanks, and there are some acidic properties in industrial grade Co2, which will over time work away at the inside coating and produce minute flakes of material (solids) to enter the tank. These will settle with no problem at the bottom of the tank. Undisturbed they will present no problem, but it will only take a very minor piece of solid to get under the diaphragm or rubber to stop the spring closing it. If that happens you will still get a flow of Co2 when the solenoid is "off". Springs can be bought but finding the right one is problematic.

The acids and surfactants in FE's and industrial tanks can rot through none Co2 piping, so don't listen to people who say "I've used air line and never had a problem"! Well done you.... but just saying.

Tip; Always stow your Co2 vertically, never on it's side, never especially try using the cylinder on anything but the vertical! I'f your using an FE it's a good policy to operate the trigger ie close it from time to time or even when you switch it off, the seals in the handle valve are not designed for continued use in the open position. Unlike knobs used in commercial bottles.

If you try to use Co2 in any other position then vertical you run the risk of pushing liquid Co2 through the valve. I saw a post where someone recommended tipping the bottle upside down in water to check for leaks!!! NO. This is putting liquid Co2 into your manifold and you are asking for trouble, also this will allow any sediment in the bottom of the bottle to come up and enter the manifold, jamming the solenoid as above!

Tip; When you connect up your manifold, just put a little bit of washing up liquid in water and brush it over the joints. If there is a leak you'll see bubbles. Also there should be no need to use PTFE tape on the manifold thread, although if you do and can still tighten it against the seal on the bottle then fine, but its the nitrite rubber seal which seals the manifold to the tank.

Final tip;- after the bottle has been standing upright for about twentyfour hours, crack the handle without the manifold connected, you'll hear and feel a very powerful flow of gas but don't worry, just for a second, this will clear any detritus from the valve itself that may find it's way into your solenoid.

Final, final tip. Connect your manifold and let the bottle stand unmoved for twenty four hours, I know this sounds a little OTT but it's belt and braces to protect your solenoid. Also strap or tie your bottle in place so nothing or no one can accidentally knock it over, dogs, small children etc...

Connect it up and enjoy, get good equipment, cheaper manifolds have very dodgy valves to control the drops of Co2. You may find your bubble count varying. Never leave the Co2 on over night, the plants need to sleep and also take up nutrients and they don't photosynthesise in the dark so can't use Co2. I run a smart home and have my Co2 on a timer to come on an hour before the plant lights and switch off an hour before they go off, but you can vary that to whatever makes you comfortable, just know there is no gain to running Co2 over night, it could damage plants, and heaven forbid if there is a catastrophic manifold failure causing a Co2 "dump" into your tank and killing everything at least you'll be awake to catch it. Apart from that your wasting all your Co2 running it 24 hours.

If you get problems, solenoids can be stripped down, and invest in a small bottle of compressed air and blow everything through, never poke at the rubber or stick anything metallic in there. use cotton buds or something to clean the armature and the pocket it sits in.

Sorry for the long post, hope it helps and prevents some manifold failures.

Kia Kaha, Phil.

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