What makes a CO2 tank burst?

[Leper]

I dont know if this should really go in Air Systems, but I'd like as many people as possible to see it.

Ok, I'll try and make this long story as short as I can, because quite alot happened.

Today I played my first game with my new gun, and at the very end I asked for a CO2 (my tank is 12oz) fill so I could use it at home. I noticed that the guy didn't seem to be weighing the tank (more on that later). I get the tank back, he asks how my day was and I tell him "Pretty good, thanks".

Later on, on about 25-35mins into the drive home (maybe 45 mins after the fill) the gas tank seemed to just explode with CO2 spewing everywhere. There was absolutely no warning and scared the sh*t out of me. I immediately wound down the window and stuck it out to let the gas into the open.

Fortunately, my friends mum is a nurse and managed to help out with the cold burns on my hands and once the inital shock went past, my friends parents were pretty cool about the whole issue (I was expecting them to go ape sh*t at me :( )



Ok, here's the important part:
I assume that what happened was that the burst disc kicked in, but what will make that happen. My dad phoned up the field and the owner said that this "happens quite often when the tank is taken into a warm car". Is this BS, or what? I have no experience with this sorta thing whatsover so I'll appreciate any examples / info that you guys know of.

Oh yeah, the owner said that they weigh the tanks, but from what I saw the guy never hung it up on some scales or anything, and that's what makes me suspicious about the warm car thing.

Thanks for any help!

[Magnus55]

From what I know, I'm pretty sure they're supposed to weigh the tanks so they can release excess CO2 or pump more in accordingly, so your tank comes back to you full and not over or under filled. If he didn't weigh it, then there was no real way for him to tell if he was overfilling your tank. I think you have a legitimate arguement. On a side note: you get them to replace your tank? If you really wanted to, you could pressure them into giving you a larger tank or a whole bunch of free stuff, seeing as you suffered injury to yourself due to the incompetence of one of their employees, and might have even crashed the car from the sudden explosion. *hint hint* grounds for lawsuit. :wink2:

[Leper]

I've already talked to my parents about lawsuits :)

The problems are:
1) It's my word against theirs on the weighing thing. It was the end of the day so there were no other players around to witness it.
2) My hands recovered really nicely (a good thing) and there doesn't seem to be any damage or blistering.
3) Not meaning to cause any contoversy or anything, but I don't think that the British laws would work as well in this situation as the American ones.

That's a really good point you have about a "potential car crash" :)
If it was a result of them over-filling, from what I've read, that would have weakened the tank so I'll definately try to get a new one off them. I'll see what happens.

[_DeaTh_]

the same thing happened to a friend of mine ,except his grandparents were in the car and almost had a heart attack........

it is true when u'r tank gets to room temperture or hotter the seal inside will let out the air instead of letting it just explode .......
next time put it in a cooler or some kinda insulated carry case or if u don't got one then wrap it in a shirt or somethin and turn the air condition all the way up........

as for the law suit thing i can't really help u there....
:eyes:

[Codestar20]

How hot did the car get? I am guessing the guy was being lazy and overfilled it. With the right amount of co2 in the tank that is supposed to be in the tank (i.e. 12 oz should have no more than 12 oz in it) the burst disk shouldn't go off unless it is overheated (about 120 or hotter). Burst disks are rated 1800 psi at the least. And the hotter it gets or the more over filled it is the higher the psi which is definately not good. I'd go have a talk with the field owner/manager to tell him about it.

[NICKYB]

ahhhhh the joys of nitro....

i think they are the result of overfilling a lot more then they are the result of heat.... my friend got his filled in the mall once and like 20 feet out of the store it exploded and he dropped it and it was spinning in circles on the ground at like 1500 miles an hour for a minute or two...

[elTwitcho]

A combination of being filled too much and heat. When the tank was being filled it was cold so there was less pressure and it didn't burst right away. As the pressure increased from heat, the burst disk went. It's definately the fault of the fool who filled your tank

[KOTOWA]

Go to court, and win the case, and get a Nitro Tank!!!

[Leper]

Thanks for all the info so far guys.

From the look of things, I'll have a hard time to get anything back from the field. It seems that it was the owner who was filling the tanks that day, so it's not helping my case at all. The only witnesses I have are the guys in the car, who can say that the tank was just in between my feet and not being bashed about when it blew.

[Ebonclaw]

Well, the owner's right that it could happen from suddenly going to a warm environment. When the CO2 suddenly warms up, it becomes a gas too fast for the tank to accomodate it. It's like the principle that if you blow up a balloon slowly, you'll get it much fuller before it burts than if you hooked it up to an air compressor and suddenly started pumping air into it. The CO2 expanded too fast for the tank to accomodate and so the burst disk blew......as opposed to the tank rupturing which would have been far worse (think grenade.) However, it could be a combination of overfilling and quick expansion of a liquid to a gas. Things expanding form heat can do all sorts of things, crack asphalt, warp metal....the list goes on. Just glad I use nitro.

[Head Hunter]

I've played 7 years and work part time is a paintball store. It does happen quite often.

The good news is that the burst disk is a SAFETY FEATURE.

In your case, it WORKED PROPERLY!

Hard to sue when the safety equipments works like it was designed to do.

Next time, and there will be a next time.... it won't be so scary. You will recognize what is going on. Hopefully, the person driving won't wreck the car. The trunk is better than your lap.

NOW. WHAT HAPPENED, WEIGHING TANKS, ETC.

When you fill a CO2 tank there is a siphon inside the supply tank that takes liquid CO2 only and sends it to your tank. As the supply tank empties the gas CO2 in it fills the top of the tank and the liquid remains in the bottom until the last of it expands into gas. This gas in the supply tank also pressurizes the supply tank to push the liquid into your marker tank.

Now some Boyles Law Gas Physics:

Gas - not liquid-, in a confined space (a sealed tank)is at some pressure. If you heat the gas, pressure increases. If you cool the gas, the pressure drops.

Liquid CO2 is just a liquid. Like water. These liquids will turn into a gas state when they are heated enough.

The 'boiling point' is determined by it's temperature and its PRESSURE. Water goes boils at 100 degrees centigrade at sea level and at 95 C at 12,000 feet (lower pressure).

Raise the PRESSURE, You raise the boiling point.
(Your car radiator would boil off all the water in it unless it was pressurized.)

Lower the PRESSURE, you lower the boiling point.(You put enough vacume on water and it will boil at room temperature).

When you fill a CO2 tank you open the valve.. The supply tank equalizes to the SAME PRESSURE as the fill tank while pushing liquid CO2 into the fill tank.

There is no adjusting it. That pressure is determined by the temperature of the tanks. You get more pressure on a hot day than on a cold day.

They only question is HOW much liquid CO2 did you get into the fill tank? Did you give the customer a proper fill? How do you know when your supply tank is empty? If it was empty you just pressurized his fill tank with gas CO2 and he will get about 6 shots out of it.

This is where the scales come in. It will be a lot lighter if it was filled with gas and not liquid. The use of the scales is the most common way to determine when you reached the bottom of your supply tank and need to switch tanks.

If the fill tank doesn't reach a certain weight, then you have a partial or no liquid fill and need to switch tanks or you have a pissed off customer.

But you have to know what each different CO2 tank weighs empty. Some are steel, others aluminum. 9 0z, 12 oz, 16 oz, & 20 oz. Different manufacturer use different amounts of tank material. etc. etc. Very time consuming to reset the scale for each tank.

An experienced filler can hold it in his/her hand and determine if it is full or not. You can feel it slosh inside.

It sounds different when liquid is running through the hose than when gas is running through it (when it is empty)

You will notice a lot of ears being held to a CO2 tank during a fill.

If you just switched tanks this morning you don't have to worry about it at all until you've fill 50 + 20 oz CO2.

We built a teeter totter 'scale' to set our big supply tanks on. With a little trial and error with the amount of weight we use to counterbalance the big supply tank with, we finnally determined what a 90% empty tank weighs.

When it gets below 90%, the teeter totter tips from one side to the other (1/2" total vertical movement)and lets us know we need to change our supply tank. We put a mark on the wall to match the top of the CO2 tank. Easy to see. We don't care how much it weighs, just when it is almost empty.

So the use of scales are not a factor in the proper and safe fill procedure. Scales are used just to monitor when you need to change your supply tank and keep your customer happy.

SO WHY DID THE BURST DISK BLOW?

SIMPLY, TOO MUCH PRESSURE.

Only one thing can increase the pressure of a gas in a sealed container. HEAT.

Several things contributed to this:

Most obvious was the ambient temperature inside the car. Your hot little hands holding it between your warm little legs. Right?

The TEMPERATURE of the SUPPLY tank.

The TEMPERATURE of the FILL tank.


NOW SOME MORE BOYLE'S LAW AND GAS PHYSICS.

You have a sealed container of a known volume full of gas. Double the temperature, you double the pressure (in centigrade).

You have a sealed container of a known volume full of gas. Compress the gas to half its original volume and you double the pressure.

While you compress the gas to half its original volume, the temperature of the gas doubles.

Do all that at the same time and you get a lot of pressure increase. Enough to pop a burst disk.

That is EXACTLY what happens inside a fill tank. The liquid CO2 takes up space and literally compresses the gas CO2 in the bottle until the pressure is equal to the supply tank.

To get a properly filled CO2 bottle, the store alway vents all the liquid and gas CO2 out of the bottle. This simply chills the bottle. It gets COLD. If it was flat empty, they do a partial fill and then vent that to CHILL the fill bottle.

It lowers the temperature of the gas inside the fill tank. When the liquid CO2 starts to enter the bottle it turns to gas until it builds up enough pressure for the liquid CO2 to stay liquid.
If the gas is COLD, you have less volume of gas in the bottle as you pressurize it with the supply tank while the liquid CO2 is running into it.

This can amount to 2-3 oz of extra CO2 (100 rounds worth) in a 20 oz bottle. 1-2 oz of CO2 in a
9 - 12 oz bottle. A noticeable amount for a customer that expects 400 rounds out of his tank and gets 300 instead.

You can "super charge" a CO2 tanks by super chilling it. Fill it completely, vent it completely. Fill it completely, vent it completely. At this point, you'd better be wearing gloves or you have severe frostbite.
Then fill it again.

The pressure is still within SAFE pressures because of the cold.

You'd better go play with it right away cause your burst disk is going to self destruct in about 5 minutes as that little bitty pocket of gas inside the tank warms up from -150 degrees centigrade (I'm not exaggerating here) to 50 degrees centigrade. That is a 400% increase of temperature AND and 400% increase PRESSURE as well. It will blow every time. Some of the idiots I work with do this for fun and set the bottle under someones desk to go off in about 5 minutes.

They think it is funny. Its not!

At this point you better PRAY that your burst disk works properly cause you will be 400% of the "normal operating pressure" of a standard fill at room temerature which is 900-1200 psi. That is 3600 - 4800 psi potentially. Your burst disk is rated (more or less) at 1500 psi and your standard CO2 tank is certified (New) at 1800 psi.

If the burst disk doesn't work or some IDIOT replaced it with a 3000 or 4500 burst disk for an air bottle by mistake, then you literally have a hand grenade in your hand with the pin pulled and the timer running.

When I have someone else change a burst disk, I READ the rating on the disk MYSELF and watch it go into my tank. Cause there ARE IDIOTS out there!

SO WHAT HAPPENED TO YOU?

It was the end of the day. You wanted a refill the tank to use at home. If the weather was cold, the supply tank might have been cold too. That would give you a little extra liquid in your fill tank.

You probably had a half full tank or better left in your fill tank. He vented it per procedure.

The bottle got a little 'frosty' maybe -50 F. You got a little extra liquid CO2 than you normally get. A mild 'super charge'. Was it cold when he handed it to you?? Really cold?

You put it in a warm car and wrapped it in your warm hands and set it between you warm legs.

Aren'y you glad the burst disk worked now?

Otherwise you might have set off a hand grenade in your crotch!

AND all burst disks ARE NOT CREATED EQUAL.
They are just guaranteed to blow at 1500 psi OR LESS.

You might have gotton one of the LESS ones, too.

I always carry a spare burst disks for my CO2 and Air tanks. Haven't needed one for my air yet but use up the CO2 disks in the hot summer time. The killer is my kid laying the black tank in the hot summer sun between games. It will go to 150 F. and blow. Put it in the shade!!!

The CO2 bottles will blow from time to time just because of the big pressure jumps because of the liquid to gas interactions with temperature.

Compressed air is regulated to about 900 psi and stays at 900 psi regardless of ambient temperature.

The burst disk for the High Pressure side is rarely affected because:

1. There is no liquid. It is all gas. Double the temperature from the fill. (say 90 F to 180 F in the trunk of a car) and it doubles the pressure not 4+ times the pressure like CO2 does.

AND

2. Remember when you compress a gas, it gets hotter? Well when you fill an air bottle to 3000 psi it gets really toasty warm - like 150 degrees warm.

10 minutes later it has cooled down and the pressure guage reads 2700 psi. So it has "room" to heat back up to 150 degrees in your trunk on a hot summers day without blowing a disk.

Nitro is the way to play paintball anyway. Each time you fire, a little CO2 evaporates and chills your tank. The operating pressure drops a little bit. Again and again in a fire fight and you notice they aren't doing 300 fps anymore. Maybe 250 fps. Can't get a ball break on anybody. slower. No consistency shot to shot.

Maybe raise hell and threaten to sue them and they will let you trade your CO2 tank and $30 bucks in for a 48 ci -3000 psi air tank worth $100 retail.

[ry_goody]

Something like this happened to me before. I was sitting in the garage and then all of sudden the pressure disk on my tank just blew. I figured it was because the gas was gradually getting warmer from when it was filled. So now whenever I intend on storing some co2 I always shoot out about 50 shots so I know there plenty of room for the gas to expand.

Also, you don't have any lawsuit on the field. Theres not much you can do wrong with filling co2 thats wrong except ripping people off, which apparantly he didn't do to you. Just remember not to store a full, freshly filled co2 tank next time, screw it on your gun and shoot off some shots.

[Leper]

Thanks alot guys, especially Head Hunter: that was really helpfull info.

I didn't really want to have to sue the field, I was just curious as to whether it was caused by guy over-filling it as he didn't seem to be using any method to weigh the tank, and I'll remember to fire off some shots next time also.

BTW, after the initial shock of what happened had gone past, we figured out that it was the disc that had burst, and what might've happened if it didn't :( .