How safe are pressurized cylinders? How much to fill? - The Planted Tank Forum
Old 08-06-2009, 12:35 AM Thread Starter
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How safe are pressurized cylinders? How much to fill?

Now that I am getting a co2 cylinder (5lbs), my parents are worried how safe they are. I heard that the valve's can blow off the cylinder and it can be very scary. Can a 5lbs cylinder cause injury in anyway? How much should I get the cylinder filled to? Should I tell the place to fill it or to under fill it just a little bit? What is usually the safe range of pressure before the tank blows? My parents are worried it can explode or something in my room. I was curious myself. Share any input on this please.

Thanks,
Bryan

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Old 08-06-2009, 12:49 AM
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Less danger then the gas bottle for the grill.
Handle it correctly no issues (don't beat on it with a hammer LOL).
Welding supply for the fill is what I use.

Sorry you asked questions. The cylinders are certified. 5lb can gets 5lbs of liquid. Pressure depends on temp.
When a CO2 tank is reasonably full it will contain a mixture
of both CO2 liquid and vapor.

As long as both liquid and vapor are present,
the pressure in the (CO2) tank will depend only on the (ambient) room temperature (not "fullness")
as shown in the table below:

Tank Temperature Cylinder Pressure
(F) (PSIA)
@69° 837
@71° 859
@75° 905
@77° 928
@79° 952
@81° 976
@89° 1080

The gauge pressure (PSIG) is approximately 14.7 psi less than the values in the table above. The temperature to pressure relationship is logarithmic. Thats why its not a good idea to leave a full cylinder in your trunk on a hot day.

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Old 08-06-2009, 12:51 AM

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Location: Elkhart, IN
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Around here, it costs me about \$15 to fill a 10lb cylinder. I don't know if prices vary throughout the country or not, though.

Just as long as you don't try to break the cylinder, you should be fine. I wouldn't go around dropping a full cylinder off a roof or anything

Got Plants?-6 CO2 + 12 H2O → C6H12O6 + 6 O2 + 6 H2O

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Old 08-06-2009, 12:59 AM Thread Starter
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So I should keep it very cool i suppose? Assuming that heat would cause the co2 molecules to move faster and expand due to the heat and build excess pressure causing a possible valve to blow correct? So when I put the regulator on, what will the tank pressure be at about and I'm guessing when the pressure reads really low like 100 psi, I should go for a refill?

Thanks for answering my questions guys

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Old 08-06-2009, 01:04 AM
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Be very careful not to do something to knock the top of it off (like hitting it with a hammer, as mentioned above). That would turn it into a missile. Other than that, it's as safe as standing in front of a fountain coke machine. If you open up the cabinet underneath it, you should find the tank there chained so that it can't fall over and bust the top.

While you should be aware of the hazard, they're not fragile.

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kid creole is offline
Old 08-06-2009, 01:05 AM
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Quote:
Originally Posted by PRSRocker3390 View Post
So I should keep it very cool i suppose? Assuming that heat would cause the co2 molecules to move faster and expand due to the heat and build excess pressure causing a possible valve to blow correct? So when I put the regulator on, what will the tank pressure be at about and I'm guessing when the pressure reads really low like 100 psi, I should go for a refill?

Thanks for answering my questions guys
No, you don't need to do a thing, except not leaving it in a car parked in the sun.

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kid creole is offline
Old 08-06-2009, 01:09 AM

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Location: Elkhart, IN
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When I got my tank, I warned a lady I work with (the tank's at my work at a LFS) to not knock the cylinder over because it could turn into a torpedo if the seal broke. Now she's all paranoid, and seems to think that it'll explode if she looks at it the wrong way

According to Rex Grigg's site, the low side gauge should read between 10-15 psi, and the high side around 750. When the high side drops well below 500, you should go for a refill.

http://www.rexgrigg.com/regset.html

Got Plants?-6 CO2 + 12 H2O → C6H12O6 + 6 O2 + 6 H2O

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legomaniac89 is offline
Old 08-06-2009, 01:10 AM
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CO2 tanks require a hydro test every 5 years to make sure they are still able to handle the pressure of the gas. If the tank is out of date you can't get it filled until it has passed the test. So... CO2 tanks do not suddenly wear out and explode. There is no need to ask for a partially filled tank. You don't have to worry about keeping the tank cool either your house would never get hot enough to cause a problem. It is advisable though to always secure the tank to a wall or the aquarium stand so that it can't accidentally get knocked over. I use a bungee cord to secure mine to the center back panel of my stand. The one danger with CO2 tanks is if the tank gets knocked over and the stem breaks off it can become a rocket as the pressurized gas rushes out. That is why they should be secured with some kind of strap. If you handle it carefully and secure it under your stand the danger is non-existent unless you do something silly.

Make sure that you read any instructions that come with your regulator. They need to be connected and disconnected properly to avoid damaging the regulator. If you take your time and make sure to learn how to use your CO2 rig you should have no safety issues.

When you get it filled the pressure will look low until the tank warms up. Mine sometimes takes 24 hours to get up to pressure. There is no correct high pressure number to look for since as pointed out already the pressure varies with the temperature. The high pressure gauge will stay at the same reading until the liquid gas is used up. Then it starts to drop fairly quickly.
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Old 08-06-2009, 01:11 AM Thread Starter
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I dont have a cabinet under my tank, my 20 is just on an iron stand. I guess I'll just leave it on the floor next to the tank but should I secure it down somehow? Or just leave it? It is going to be on carpet.

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Old 08-06-2009, 01:15 AM

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If you can, I'd build some kind of a base for the cylinder. Something you can set it in that has a flat bottom and is really stable.

Got Plants?-6 CO2 + 12 H2O → C6H12O6 + 6 O2 + 6 H2O

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Old 08-06-2009, 01:16 AM
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Quote:
Originally Posted by PRSRocker3390 View Post
Now that I am getting a co2 cylinder (5lbs), my parents are worried how safe they are. I heard that the valve's can blow off the cylinder and it can be very scary. Can a 5lbs cylinder cause injury in anyway? How much should I get the cylinder filled to? Should I tell the place to fill it or to under fill it just a little bit? What is usually the safe range of pressure before the tank blows? My parents are worried it can explode or something in my room. I was curious myself. Share any input on this please.

Thanks,
Bryan
I had the same problem, hell I still do somewhat. So I can completely relate. Yes they are safe, a fellow TPT member actually had one bust while he was sitting in class (a bit of a long story) and nothing too bad happened.

The next argument to be made will be how you're going to refil it, and if you really need it. Or at least it was in my case.

You already ordered it so I think you can probably just buy some straps or something to hold it in place to keep the parents happy. Personally I just decided it wasn't that big a deal, Once and a while when I'm careless I have algae attacks, or GW (but thats not too bad over vacations and stuff).

On the flip side I've done some other stuff and do some other stuff in the hobby that few people do. I started when I was going into freshman year of HS and I'll be a Senior this coming year. So most of the hobby woes are been there done that for me, and If I can help out feel free to PM me.

-Andrew
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Old 08-06-2009, 01:22 AM Thread Starter
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Ok, so i'll get some bungee cords i guess and strap it to one of the stand legs.

But new problem is, I need the nylon washer things for the regulator. I got the regulator from the swap and shop and I am going to need those washers. Where can I get them that fit the milwaukee regulator? Any place online I can order them from?

Edit: Thanks Hill, but unfortunately for me I can be a little lazy and being a freshman in college and working 30 hours a week, I constantly get lazy and don't want to change my diy and it fluctuates to much and I am constantly battling hair and staghorn algae, even as we speak. I have to use three 2 liter bottles at the moment and change one every week to keep a decent constant level. So for me, I know it is a good investment but like I said, I can be lazy with my diy. I don't mind other things but I just hate making new bottles of yeast for some reason lol. Thanks for the advice man and its good that you can relate to my situation lol.

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Old 08-06-2009, 01:55 AM
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I get my 20 lb at a local welding supplier. When I took my tank in, they exchanged the whole tank.

It's pretty safe but it doesn't hurt to be careful when putting on and taking off the regulator. Treat it like a loaded weapon. Don't point it where it'll do harm. Check the hardware store or where you get your tank filled for washers.

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mistergreen is offline
Old 08-06-2009, 01:57 AM
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You can probably get the washers from the same place that fills the tank. The plastic ones are not supposed to be re-used, but there are others called perma-seal (I think) that shoudn't wear out. I think Rex sells those, but you should be able to get them most places that sell regulators and tanks.
On securing the tank I would also suggest a couple of bungee cords.
On a flat surface you would really only need a chain in the upper third of the tank (yes there are rules and regulations about this sort of stuff), but on carpet I would anchor it top and bottom. I have also operated a bottle lying down before. It just looks funny when you're not hiding it in a stand

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Old 08-06-2009, 02:00 AM
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All the cylinders have the same size valve connection. Again a welding supply is a great source for the washers too.

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RubberSideDownOnTheLanding,
2-75g planted, 3-55g planted, 110g w/30g sump, 2018 update returning to sanity (Nutz)
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