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Thread: Oxygen tank full pressure?
12-18-2007, 12:40 AM #1
Oxygen tank full pressure?
At work I use oxygen tanks from different suppliers. They seen to have from 1500 to 2000 psi when cracked for the first time after a refill. Whats considered full? Seems like a wide range of refilled pressures at work here. If 2000 psi is full pressure I want 2000.
Also why can scuba tanks go to 3000psi ?
12-18-2007, 06:04 AM #2
I've always considered 1900 to be full till I switched suppliers about 11 years ago, now oxy's run 2300 to 2400.
Makes me mad getting screwed by the other supplier for 20 years prior to the switch.
Same way with Argon.
12-18-2007, 08:17 AM #3
I've always considered 2500 PSI full!!!
Wow, 1900 full, 2400 is a disappointment! I've been getting oxygen tanks of 2500 PSI on average. I've gotten tanks half full, or less than full before and I ALWAYS complain. They pull this kind of BS all the time. If you want to know for sure, ask a few places what full pressure is. They've REALLY been pulling BS with accetylene lately. :mad:
12-18-2007, 02:44 PM #4
All depends on the last inspection of the cylinder, new tanks are 22-2500 psi as they have a + sign on the Hydro test, older tanks may have their pressure lowered because of age and a hydro or visual inspection that has detected some degridation in the tank material. I used to know all the codes on the neck of the cylinders, but it has been 10-15 years .....and my memory is not as good now....maybe someone else will chime in that knows...Shawn
12-18-2007, 05:09 PM #5
Tanks are only filled to above about 2200 to 2400 on special order. We had some 6000PSI tanks come in special ordered for a tire shop. Weighed a ton!
Tanks are normally filled and sold by volume not pressure.
12-18-2007, 09:12 PM #6
12-18-2007, 10:19 PM #7
You cannot tell from the pressure of the acetylene if it is full. The pressure will vary with temperature. Acetylene is dissolved in acetone in the tank and evaporates as you use it. I'm sure you could weigh the tank and tell how much is in it but would only be accurate if you knew the empty wt of that tank.
12-19-2007, 12:04 AM #8
Shawnspeed is right. Look at the cylinder(not "tank"). There will be the hydrotest stamp which will tell you what the fill pressure should be. If there is a "+" shape after it it can be filled to 10% over ~2200 + 10%=2420. Also the pressure rating is at a 70º reading - if your tank is colder- it will read less(but fill volume is correct). Same for acetylene colder=less pressure (but fill volume is correct)
12-19-2007, 12:50 AM #9
What's stamped on the cylinder means very little. One of our distributers will couple a dozen or so full cylinders and several empty cylinders into a manifold bank and equalize the pressure by filling the empties from the full ones.
12-19-2007, 02:55 AM #10
Acetylene is filled by cuft. There should be writing on the bottle that says how much is in there. Check your store. If they are charging one price for all the same size cylinder and the invoice is marked per cu-ft then start bitching because thats a no-no...
12-19-2007, 08:01 AM #11
Well, you're not going to get 1/2 pressure with a 10f variance.
My barn (small pole barn with living space above) is heated because the water to the house comes up in there. So, I keep the temperature about 50f for working, and so the pipes don't freeze. I know the pressure varies with temperature, but it only varies by about 10 degrees down there in the winter. I'll go and get the exact same shape style and size accetylene tank, and it used to vary by 50%. The temperature didn't vary by 50%. They tried telling me about the temperature thing @ the welding supply store, and I told them it's heated to a consistant temperature. I guess it works for all the other people that use them at home without a heated shop. I went back up and got a full tank. Hooked it up, cracked the valve, and COLD it had more pressure in it than the other tank! I think they pull that on anybody they think they can. I noticed they had the tanks grouped by size, with 2 groups of the smaller sizes. The second tank came from the other group. Now I'll make sure I tell them which group of tanks I want my tank from. I wish they had some competition, but I don't exactly like driving around with welding tanks in my truck. The closest competition is over 30 miles away, down the craziest stretch of express way in the state!
12-19-2007, 10:00 PM #12
My Ox when first cracked typically reads about 23 to 2400. BTW the plus on the neck means the cylinder certification expires 10 years from the last date stamped on the neck. The star has a similar meaning but for only 5 years. I haven't heard of it ever having anything to do with the pressure rating of the cylinders.
12-19-2007, 10:41 PM #13
Nope + means you can overfill by 10%. A star extends the retest date to every 10 years.
These are DOT approved marking for all cylinders except for CO2 and to qualify they must have been water jacket hydrotested.
12-19-2007, 10:46 PM #14
Ok, I stand corrected. I based my previous post on what I was told by my gas supplier when I took in a cylinder I purchased at an auction to have refilled.
If the plus means they can be overfilled by 10% then there must be a pressure rating for Ox cylinders (I would imagine it varies by size?). What would the ratings be?
edit: Nevermind, I took a look at a couple of cylinders here in the shop and found it. I just never took to the time to get up to speed on the markings- which probably isn't a good thing to admit..
12-19-2007, 11:32 PM #15
So if I crack a newly refilled cylinder and its sitting at 1500, I'm getting screwed!
oldbikerdude37 liked this post
12-20-2007, 03:29 PM #16
Yep. The store should have a gauge with a hand tight fitting to check the bottle when you pick it up. If not make your own or use a regulator and check it there in front of them.
12-22-2007, 12:29 AM #17What's stamped on the cylinder means very little. One of our distributers will couple a dozen or so full cylinders and several empty cylinders into a manifold bank and equalize the pressure by filling the empties from the full ones.
Hers is the fill procedure for oxygen:
Check for contamination (dirt and oil on cylinder)
Odor test (crack valve and check for positive pressure and smell content for traces of acetylene, - if no pressure inject nitrogen and repeat)
hook to manifold (most tandem fill 10 to 30 cylinders per bank)
open all cylinders and blow down contents
vacuum pump to -20in mercury(?)
start Oxygen fill
at 1800 read cylinder temp and consult chart for finish fill pressure.
shut off at finish pressure
remove from bank
That was the "official" Linde/Praxair/Airgas methode
IF your distributor is "coupling a dozen or so full cylinders and several empty cylinders into a manifold bank and equalize the pressure by filling the empties from the full ones"
Then they are "cascade filling". This is often done by fire departments and ambulances to keep their equipment full.
Consider this: IF 5- 2400psi 100% filled cylinders are couple to 5- 0% full cylinders and "balanced" - the best you will get is 10 50% full cylinders at around 1200psi. So they took 5 full cylinders at their cost of say $5 each ($25 investment), transfilled them into 5 empties, balanced them to wind up with 10 "full" 1200psi (cough, cough) and sold each one for $25 ($250 gross), And they probably broke several federal laws to boot!
If your distributor is selling you a cylinder filled to anything less than stamped rated pressure, they are doing you a disservice and potential putting you in danger with improperly serviced cylinders(rupture hazard). You can cascade and fill a cylinder to full but that method is way more wastefully than productive. You are paying for waste ,laziness and profit gouging.
If you can't tell, I was in this business for a few years.