how much pressure

[david_r]

I think I got shorted on my Oxy tank. Fresh from the shop it's 1500 psi. I was thinking it should be closer to 2500 psi.

Did I get shorted or am I having a brain fart? To tell the truth, I never paid much attention to the high side but had occasion to hook my regulator up to someone elses tank to check my gauge and I seem to recall it reading alot more than 1500 on a new tank.

david

[7018]

The one's i get run about 22 00 to about 2500 never had one that low!!

[John C]

Take it back & get one that is full. The supplier ought to swap it out unless you've had it for a couple of days.

[Shade Tree Welder]

Plain and simple you got screwed!

[Banzaitoyota]

avg reading full is 2200

[Franz]

An O2 tank that is properly filled should show 2200psi at 70 degrees temperature. Readings slightly higher or lower are normal at temperatures above or below 70 degrees.

One of 2 things has occurred; Either the valve on that cylinder is leaking, or it's an old cylinder that has been derated and was only filled to 1500psi. Some gas distributors are, shall we say, sneaky basturds who run a lot of 1500 psi loads out the door to customers they figure won't check.

[david_r]

Interesting point Franz. What determines if it's derated? It's about as old as you :D but has a very recent hydro date on it. I think the original date on it was 1953. I don't think the welding shop is screwing me, but their supplier may be.

I think I'll be buying a CGA 540 nipple, nut and oxy gauge for the next trip to the supplier.

[Franz]

Honestly, I don't know when a cylinder has to be "derated" and quite frankly, I think the derating of cylinders for welding gasses is a crock of HORSESH!T that some suppliers are using to screw the customer.
There are 2 plants here that refill cylinders, and I've seen with my own eyes that one of them fills a compeditor's cylinders for them, and oddly, the ones with the refill capability are the used oat merchants telling their customers the derated cylinder story.
I probably own in the neighborhood of 20 cylinders, and have never had one that was "derated". I have had cylinders that came to me with bad valves, and they were definitely underfull when they slid across the dock. The guy who unhooks the cylinder from the manifold at the fill plant is supposed to check the valve after unhooking and before screwing the bell on, but I doubt they do.
One thing that has interested me for a while is that Co2 cylinders have a brass cap for the valve, but the caps don't seem to be available for oxygen cylinders.

[Paychk]

From what I understand the cylinders get de-rated when the hydro test is done. I guess the cylinder isn't safe at the higher pressure so down it goes. In stead of shafting customers they aught to de-rate them for CO2 cylinders and make use of them that way.

[Shade Tree Welder]

Don't believe the derated horse**** you are being fed. A cylinder that does not pass hydro that means it split/exploded and has a f***ing hole in it or is in peices. Oxygen, argon, nitrogen etc. are hydrotested at 4500 psig. If they fail they blow. Seen two do it. The first time I needed new underwear.

Acetylene due to that they are low pressure tanks and filled with diatomeaous earth and acetone are never hydro'd. SCUBA and SCBA tanks witch have a working pressure of 4500 psig are tested at 9000 psig.

Hydro testing cylinders involves removing the valve filling the cylinder with water. Then the testing valve and hose are attached. During the test the cylinder is submerged in a tank filled with water. Our tank was 1" HY100 steel and acted as a scatter sheild. When they are test the pressure is brought up to and maintained at 4500 psi for 30 minutes (USN procedure).

[bikeitswift]

After lugging an actelyne tank home, dragging it to the back of my shop and hooking it up to find it empty (I noticed that they were not astounded to see this, but rather, "Oh, another one??"), I now ask the shop to put a gauge on it and let me see how full it is. They seem to understand, and I notice they have a number of gauges lying there to do just that. I wouldn't bother hauling the tank back, but I'd tell the shop. and say when you do bring it back they owe you a freebie- a good shop will.

[SDean]

I don't know when a cylinder has to be "derated"

"Derated" may not be the proper way to express this. Most of the cylinders that we use in welding are "plus" rated over their base service pressure. (Except CO2) This "plus" rating allows the filler to overpressure the cylinder by 10%. Thus a 2015 cylinder (92/125/155sz) can be filled to 2216psi at 70 degrees F., a 2265 (281sz) becomes 2491psi and the 2400 (336sz) is filled to 2640 psi.(there are some older 1800psi cylinders in service, but none that I know are ever allowed to have a "plus" rating, and are mostly used for CO2 service)

So a cylinder can be "derated" back to it's basic pressure and still be in service, but make sure that they don't charge you for product that you didn't receive.

The sizes we know the cylinders as, like a 155cf Oxygen, is that size cylinder filled to 110% (2216psi). That same cylinder filled at 100% (2015) would be a 140cf Oxygen.

DavidR said:
I think I got shorted on my Oxy tank. Fresh from the shop it's 1500 psi. I was thinking it should be closer to 2500 psi

It should only be near 1500psi if it was very cold! You probably were shorted. Have them put a gauge on it before you load it.


Shade Tree Welder said:
A cylinder that does not pass hydro that means it split/exploded and has a f***ing hole in it or is in peices.
A cylinder can also fail hydrotest if fails it's elasticity parameters.


Are we less confused now? Well, at least now our confusion has meaning and direction.:D

[david_r]

Thanks for all the info guys. Very informative.

I'll probably mention it to the welding shop so they know they may have a problem with their supplier. I don't think I'll be asking for anything as I feel like they gave me a pretty good deal when I upgraded my little tanks to 125s.

[MAC702]

Is the +10% for filling them without cooling? And then when they cool, they would drop back down to normal full pressure?

Or is it for being 10% overfull for delivery to customer?

[SDean]

Is the +10% for filling them without cooling? And then when they cool, they would drop back down to normal full pressure?

The fill plant will monitor the temp of the cylinder and overpressure them so that when they cool back down (to 70 degrees F) they will be at the proper pressure. Either 100% or 110% if it qualifies for the "plus" filling. Most 2015/2265/2400 cyls are filled at 110%, unless they are really old, say pre-1955'ish.

[Snidley]

Around here anyway - if your cylinder fails hydro - its returned with either a hole drilled in it or the valve is removed and the threads have received the chisel treatment.

Those are the only options.

[david_r]

Snidley,
Most places I've seen here (Southern California) have an understanding with the customer. We buy the tanks from them and COULD exchange them anywhere we damn well please but take them back to the seller for refill (actually exchange). In consideration for this business, they assume responsibility for the costs of hydro testing.