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View Full Version : How long will a tank last?



Poppy360
08-30-2007, 02:04 PM
I recently purchased a 3200HD and would like to purchase a 75/25 tank for it. The only two feasible options are a 20lb tank for $106 or a 60lb tank for $182. How long will each tank last? I know a definite number can't be given but I'm looking for a guess-timate.

Thanks!

TSOR
08-30-2007, 02:20 PM
Divide your flow rate into the tank volume.


example: a 20cu/ft tank wil last for 1 hour at a flow rate of 20cu/ft per hour (CFH)

jjsjeff
08-30-2007, 03:11 PM
I recently purchased a 3200HD and would like to purchase a 75/25 tank for it. The only two feasible options are a 20lb tank for $106 or a 60lb tank for $182. How long will each tank last? I know a definite number can't be given but I'm looking for a guess-timate.

Thanks!

I can't really recommend a size of tank for you. It kind of depends how much weight you want to lift. One of my coworkers said to refill his little tank is barely cheaper (if at all) than refilling his larger tank.

P.S. I bought the same welder, but I run flux core on everything. Waiting for gas until I build a cart to hold my welder and plasma cutter + future gas bottle.

KTI
08-30-2007, 03:22 PM
One of my coworkers said to refill his little tank is barely cheaper (if at all) than refilling his larger tank.
in cost of filling a bottle 95% is a cost of labor and 5% is actual cost of gas. That's why (at least here in IA) filling 20lbs CO2 bottle cost only $2 less than filling the huge one (I don't remember - about 50/80lbs). Thats why you should get the biggest one you can afford.

WelderBoy
08-30-2007, 03:28 PM
in cost of filling a bottle 95% is a cost of labor and 5% is actual cost of gas. That's why (at least here in IA) filling 20lbs CO2 bottle cost only $2 less than filling the huge one (I don't remember - about 50/80lbs). Thats why you should get the biggest one you can afford.

Yup, I found this to be true at my LWS as well.

Poppy360
08-30-2007, 05:07 PM
Welp, it's definitely an issue of cost so the 20# tank it is.

I just got done doing my first welds ever! :cool2:

I used the flux core on some 1/8" and 3/16" plates. Not too shabby but I definitely need a lot more practice. Once my fiance gets home with the camera I'll post some pics.

The 1/8" was easier initially but I think I was running it too hot. The end of the welds were concave as compared to the plate.

The 3/16" took more adjusting with the speed of the wire. At first the welds were porous so I re-wire brushed the metal and tried again. Same results. I upped the speed a little and that helped greatly. The welds actually looked pretty good. :)

My first project is making a welding table so that I can get off the ground. :p

gnm109
08-30-2007, 06:57 PM
I recently purchased a 3200HD and would like to purchase a 75/25 tank for it. The only two feasible options are a 20lb tank for $106 or a 60lb tank for $182. How long will each tank last? I know a definite number can't be given but I'm looking for a guess-timate.

Thanks!


If you are getting a bottle of 75/25, you are buying cubic feet rather than pounds. A 20 cubic foot bottle would last one hour if you were set at 20 cu. ft per hour flow.

CO2 on the other hand is sold by the pound. one pound of C02 equals approximately 8 cubic feet of gas since .1234 pounds of liquid compressed CO2 yields one cubic foot of gas. I use C02 from a 20 pound bottle with my MIG welder. A little more splatter but the bottle is compact and yields about 8 hours of welding since it is equivalent to 160 c.f. of gas.

737mechanic
08-30-2007, 07:32 PM
You can get a 80 Cubic foot tank brand new on ebay for $137 shipped to your door. You have to fill it at your local gas supplier but it only cost me 18 bucks to fill at Gasco.

They also have the 20 and 60 Cubic feet tanks on there and they are a bit cheaper.

I went with the 80 because it would cost me $15 to have a 20 cubic foot tank filled so for another 3 bucks I get 60 cubic feet more gas. It is a little more money up front but over the long run it will save you money and trips to the gas store.

Poppy360
08-30-2007, 08:41 PM
So, you can use straight CO2 instead of the 75/25 mix? What are the advantages/disadvantages of each?

TozziWelding
08-31-2007, 11:00 AM
Straight CO2 is cheap as dirt and lasts for ever, just a little more splatter. Heavy equipment buckets cant tell the difference.

Poppy360
08-31-2007, 11:42 AM
I have a LOT of CO2 that I use for my home brewing and for my jeep. Maybe I'll stick with that...

TozziWelding
08-31-2007, 11:44 AM
You are gonna need this adapter http://store.weldingdepot.com/cgi/weldingdepot/A809.html
to use on beer tanks.

MoonRise
08-31-2007, 12:33 PM
Straight CO2 - a little more spatter and a little deeper penetration. The penetration is helpful if you are working on thick(er) steel, not so good if you are working on thinner sheet metal. Cheaper. You are supposed to use a slightly different regulator with straight CO2, at the very least you'll probably have to get a fitting adapter to connect your regulator to the CO2 tank (different threads). CO2 is compressed liquid, you have to use the tank upright and be aware of the cold from the boiling liquid (don't get/let the liquid CO2 in your regulator or on your skin, etc)

75/25 Ar-CO2 - cleaner and neater welds, better than CO2 on sheet metal. More expensive than straight CO2, but uses the regulator your equipment most likely came with.

A 20 cu ft tank is relatively tiny. About the only reason to get one is if you -need- the portability. It will cost almost as much to fill a 20 ft3 tank as it does to fill a 40, 60, or 80 ft3 tank. Each is within literally a few dollars price difference on the refill for 2x or 3x or 4x the amount of gas.

At a gas flow rate of 20 ft3/hr (standard small MIG gas flow rate, give or take a little bit), a 20 ft3 tank will last one hour. The 80 ft3 tank will last 4 hours.

20 ft3 tank = $106 + 3x$28 = $190 for 80 ft3 of gas (4 hours arc time at 20 ft3/hr flow rate)

To get 8 hours of arc time from that 20 ft3 tank, you'll have to refill it -another- 4 times. Drive back to the LWS, refill/exchange the tank, drive home. Cost for that 8 hours of gas is now $190 + 4x$28= $302.

80 ft3 tank = $198 for 80 ft3 of gas (4 hours of arc time), next refill would be ~$35. Cost for 8 hours of arc time = $198 + one refill at $35 = $223

Prices from Cyberweld. Also check IOC. See if you LWS will price match or do a little better on their original pricing on the tank.

Generally, get the biggest tank you can afford and handle weight/size-wise. It's less expensive that way.

Poppy360
08-31-2007, 12:39 PM
Thanks for all the info!

smithboy
08-31-2007, 12:56 PM
Moonrise mentions that striaght co2 is liquid. One problem I have seen is frozen regulators...but, that usually is because of a tank leaning or flowing too fast. If you are just learning, mig, co2 will give you a lot of practice for the $...

gnm109
08-31-2007, 03:08 PM
I have a LOT of CO2 that I use for my home brewing and for my jeep. Maybe I'll stick with that...


I really like C02 due to the lower cost and the excellent penetration. Generally the 20 pound bottle will read 900 psi when full. This is temperature dependent, of course. The tank will go until it's almost empty and then the pressure will drop almost immediately. I'm a hobby welder myself so a tank lasts me about three months at 8 hours of welding.

I control the splatter quite nicely by keeping the tip extremely clean and well-coated with nozzle gel available at the local LWS. I also clean the tip with a rag and dip it in gel when I put it away so it's ready for next time.

I haven't welded with 75/25 but I've been very pleased with the penetration of the C02 with my 220VAC SP175 plus Lincoln. It will easily do a nice fillet on 1/4 inch steel at a little below full power. What's not to like about that ?