Bottle refill problem

When i recently refilled an 80 cubic foot bottle with argon-25 (argon-co2 mix), i noted that the pressure (on the full bottle) was 1500psi. I had thought a full bottle would read 2000 psi. My conclusion is either:

a. regulator is damaged. regulator is harris, 10 years old. Is it common to have these service every 10 years (with little use)? How do i determine if regulator is damaged?

b. temperature has affected reading on tank. ambient air temperature is 70 degrees f.

c. distributor filled 75% of tanks capacity, i.e. 60 cubic feet (& charged me for 80 cf).

should i bring a regulator when i refill, to check tanks capacity before i leave distributor?

TIA
regards.


this is the newly filled tanks regulator w/guage:


this should be 2000 psi on a full tank?

check the valve on the tank maybe it has a slow leak and lost gas after filling

yea i would ask the shop that did the fill. i just recived a full tank (150 cf) and it reads ~2300 with a 60 F ambient temp

A little late, but here's a link over at the hobart forum that discusses the likely cause:

Tank Pressures

The gist of it is that your bottles were probably filled to about 2000 psi on the spot (during which time they got hot) - i.e. the place was probably in a hurry to fill your bottles in 10 minutes or less and didn't keep the bottle cool during the process. On the way home, the bottle cooled and the pressure dropped. Probably the most likely reason, but still good to check your equipment for leaks. I doubt they intentionally short-changed you.

I suspect exchanged bottles are less likely to have lower pressure when you receive them, as they are probably either filled in an automated and controlled environment, or they are filled more slowly and/or cooled during filling.

Chad

Couple things...if you close the bottle valve and remove the gage entirely, does the high-pressure needle go back to zero? If so the gage may be OK.

Also...what prompted you to refill at that point? Normally I start making a mental note about the time it drops below 500 psig and then self-inflicted dope-slaps start when the puddle goes funky at *the end* and I still hadn't exchanged

I exchanged a 60 cu ft bottle. My regulator registered 1800 psi.

Mark

chad: thank you for that link, it was informative. since the tank has a plus sign at the last test, it is rated for 10 % over, 2200 psi. the shop (i believe) should have charged it to 2200, to compensate for the heat (i recieved it quite warm), so when it cools to ambient temperature (60 deg f), it will be 80 c.f.. This raises the question about temperature conversions, when a tanker truck delivers fuel to a gas station, the fuel is sampled for specific gravity and temperature, looked up in a table that corrects to 60 deg f., and only then is the correct volume of gasoline determined (API conversion to 60 deg f., IIRC). So, should'nt the distributor do the same thing (more or less) for compressed gas? If not, then you don't know how much gas you are receiving (if tank is hot), however if tank is swapped out & cool, it should be 2000 psi (-or- the distributor could say -i filled it to 2000 psi, but it cooled off now- & you get less than a full tank.) there are regulations about weights & measures, but i don't think they apply to compressed gasses (AFAIK).

matt;
i refilled an empty bottle, when i got back from the filling i connected the hoses, & found 1500psi, and was surprised, i expected to see 2000 psi.
i tried your guage test, when i loosened the nut, the needle immediatly dropped to zero. i need further testing of the guage somehow, (new guage is about $100 or so). the odd thing is that this is a reputable distributor, unfortunately it is not cost effective for me to fix this problem, unless it gets much worse (refill of bottle: $28, cost to get to dealer @ 9 miles per gallon, round trip $7).

i was thinking of an alternate procedure to identify if tank is full, by weighing the bottle while empty & when full to determine if it is full. this should be definitive (although my scale is not very accurate).
maybe i need a larger bottle.

I think weighing it will correlate nicely with the fill left.

However, should you decide to "bleed" off a tank to zero to establish that data point please do this outside the shop in the great outdoors!

Aside, I have always had "new" tanks come in north of 2000 psig also.

9mpg? That's gotta be a dually.....

matt:

9 mpg, is for a 1999 chevrolet 3500 cargo van tare weight 6,000 (with a fixed load of 2,000 lbs of tools & supplies = 8,000 lbs), 5.7 ltr engine, 4.11 rear axle, city driving with air conditioning off. if air cond. is on, i lose apx 2 mpg. thank you GM

i had considered a diesel engine at the time, but felt that it would not put off enough heat in the winter-time (diesel engines run at a cooler temp 180 deg, than gas 210 deg, or so). i should have ordered the diesel(i am sure i would get at least 14 mpg), in retrospect.

My last repair shop was in a warehouse with a fill plant. They fill 20 AR bottles at a time measuring temp as they go. Even if tank is rated 10% over they never fill past 1700 or so. They have a chart of temp vs pressure and thatswhat they stick to.

macona,
that is what i am getting at,
if they fill the bottle at a specific pressure, and temperature, then the volume can be calculated.

a bottle must be filled to max capacity, to get a full charge. for example, if an 80 cf bottle is charged quickly to 2000 psi (& gets hot), when you bring the bottle back to the shop, you will find less (ex, 1500 psi). therefore although you have paid for 80 cf, you got 60 cf.

i assume that the distributor is an expert, and therefore knows exactly how much gas i am getting. that is why it is an issue to me.

regards.

"if they fill the bottle at a specific pressure, and temperature, then the volume can be calculated."

The so-called "Ideal Gas Law":

PV = nRT, where

P = pressure
V = volume
n = Avogadro's Number
R = the universal gas constant
T = temperature

Given any two, solve for the third.

n and R are constants.

Actually they never fill to 2000 psi at all. The tanks never get hot enough to bring the pressure up to that pressure. Next time I see one of the guys from the fill plant I will ask them exactly wht the procedure is on determining fill.

Go back and query the fill pressure with your agent. While you`re at it take your regulator and gauges along and test on one of their filled bottles; if it reads low then try with a new gauge from their shop - a cheap test option and might reveal a lot more?
Ken

To PETERH 5322 or anyone else, do you have the Avogadros and universal gas numbers for CO2 and Argon? Or better yet a link to all of them?
Thank You For Your Time, Mike

Hi, Petreh 5322. I found the information that I asked you for. Thank You for putting me on to the gas math.
Thanks again, Mike

You are definitely getting shorted if they aren't filling you to at least 2000psi, and with a plus should be 2200psi. As far as welding gas I swap tanks and they are usually 2100psi.

You really have to trickle fill them to keep the temperatures in check. But 80 cuft isn't a large volume to fill properly within a reasonable amount of time.

I do quite a bit of diving and usually use either my 3441psi 120 cuft or my 2400+ (2640)psi 108 cuft tanks. If they are going to hot-fill them (fast under 10 mins.) they usually fill them around 4100 and 3200 psi respectively. By time I am ready to hit the water they are right close to max operating pressure. All DOT tanks can handle double max operating pressure, so there isn't really any risk of the temporary high pressure.

I find it quite unexcusable to short you that bad, considering they are certified gas mixers, I would go back and tell them to fill it to 2200 or learn a lesson and find a better supplier. 30% is a lot of gas and at current prices they better give every last molecule.

how can i get my hands on a bottle of 75/25 ?