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-   -   3.5 oz. vs. 4 oz. (http://www.mcarterbrown.com/forums/ask-experts/47554-3-5-oz-vs-4-oz.html)

LagShock 08-07-2008 01:06 PM

3.5 oz. vs. 4 oz.
 
Ive seen tanks labeled as 3.5 oz and 4 oz. Is there any difference between them besides the label?

TrojanMan 08-07-2008 01:23 PM

The 4 oz. tanks are older and most of them were sold through Brass Eagle.

Generally, the 4 oz. tanks are steel (versus Al-Mo alloy for the 3.5) and they are significantly heavier.

The shape is different and the 4 oz. tanks are slightly larger in diameter. I'm not sure if they exceed the 2" rule and since I sold my old 4 oz. I can't just caliper it but I know they're very close.

The 3.5s are under 2" in diameter and thus never need re-hydro.


Don't worry about getting a 4 oz. tank, if that's what you're wondering. They're heavier, older and are prone to corrosion. The 3.5 is a better choice if you're looking to buy, plus it's easily available.

LagShock 08-07-2008 01:30 PM

Thanks for the quick reply.

If one were to put 4 oz of co2 in a 3.5 oz tank, would anything terrible happen? It doesn't seem like the pressure inside the tank would increase any, unless the tank was completely full of liquid at 3.5, in which case terrible things would happen. Then again, I haven't taken fluids yet.

Any thoughts?

russc 08-07-2008 01:36 PM

It would blow your burst disc, most likely. I believe co2 tanks are rated to hold co2 at 2/3 liquid or something, so yes you could fit more in but it wouldn't leave room for expansion and would result in a pressure spike and blowoff given heat and time.

tymcneer 08-07-2008 01:37 PM

On a hot day, you risk popping the safety burst disk.

More information is here. The folks at Warpig explain it pretty throughly.

Ty

ScrapIron 08-07-2008 02:13 PM

as mentioned earlier, if you get a 3.5 oz tank make sure it only gets 3.5oz fills.

I was playing a scenario in Illinois and went to get CO2 fills on my tanks and I didn't say anything other than "fill these up for me" and "please"
About an hour later the game is started and while walking to the HQ the burst disk blew out on the 3.5 that I had on my MKX launcher. So I turn around and head off field to get it fixed. When I take it to the fill station I asked the guy for a fresh fill after just having replaced the burst disc. Sure enough, I get back out to the base, set my MKX down to start filling out a mission card and i hear its burst disc pop again and vent again.
Now i'm ticked, I go back to the fill station and find out that the guy had been giving it 4oz fills the whole time. Since I was out of burst discs the air jockey that had been over filling it scavenged a new burst disc from a rental tank of theirs. He was really apologetic, but now I just know that unless I'm filling it myself I always clearly state to the fill station personnel the exact amount that the tank can hold as i hand it to them.

HP_Lovecraft 08-07-2008 03:00 PM

I've made it a habit to always watch the scale, if possible.
Under and overfilling are very common.

I had one guy only put 12oz into my 20oz tank. When I questioned, he told me the tank does not say 20oz. It says 1.25lbs, and he doesnt have time to do the math, so put in 12oz "just to be safe".

Lots of fields PURPOSELY underfill all there tanks for the stated reason "to prevent burst discs", but thats garbage. They are ripping off customers, since a properly filled tank should not burst its copper.

That said, I've also seen fields that OVERFILL. They tech gets into a chill/fill rythym, and stops paying attention to the scale.

Anyway, avoid the 4oz tanks. They are not exempt from hydro because they are steel, and since they have not been on the market for almost 10 years, none would be legal to use. Also, you can not annodize them (if that interests you).

Uranus 08-07-2008 03:15 PM

I hardly ever see any one weighing c02 tanks. they just fill them until they don't tank any more. I like to fill mine at home.

ThePixelGuru 08-07-2008 08:31 PM

Quote:

Originally Posted by LagShock (Post 478862)
If one were to put 4 oz of co2 in a 3.5 oz tank, would anything terrible happen? It doesn't seem like the pressure inside the tank would increase any, unless the tank was completely full of liquid at 3.5, in which case terrible things would happen. Then again, I haven't taken fluids yet.

No. No, no, no, no, no, no. I don't put 12oz in my 9oz tank, I don't put 16oz in my 12oz tank, I don't put 4500psi into my 3000psi tank... Would it work? Most likely. Would anything bad happen? Probably not.

Should I do it? Absolutely not. It's rated at what it is for a reason.

Yomama101 08-07-2008 10:25 PM

Quote:

Originally Posted by HP_Lovecraft (Post 478970)
Anyway, avoid the 4oz tanks. They are not exempt from hydro because they are steel, and since they have not been on the market for almost 10 years, none would be legal to use. Also, you can not annodize them (if that interests you).


Bottles 2 inches in diameter or less, and less than 2 feet long DO NOT have to be tested.
"The 2 and 2 rule."

Requalification (HYDROTESTING) not required per the note under table 1 in 49CFR part 180.205. The note reads, "Any cylinder not exceeding two (2) inches in outside diameter and less than two (2) feet in length is exempt from volumetric expansion testing."


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