Selecting a gas bottle size and refilling options
You are still not done once you have the welder and your personal protection equipment. You need a controlled flow of argon gas to protect the molten metal pool from the air when making the weld with the tungsten electrode and filler rod. Your regulator / flow meter will connect to a standard valve on a portable gas cylinder, which usually rests behind the welder on the welding cart.
Several questions must be answered before you can acquire a cylinder of gas:
- How big should the tank be?
- Should I lease or purchase a tank?
- If I purchase a tank, should I have it refilled or exchange it for a full one?
Answering these questions requires you to consider your goals and capabilities, such as how much welding you plan to do, how physically able you are, and how sensitive you are to value vs convenience.
The size of a compressed gas cylinder will depend upon your cart capacity, your lifting ability, and your projected usage rate. Clearly, the larger scf tanks weigh more empty and full. If you weld only occasionally and cannot lift more than 80 pounds, you probably want a small to mid-sized tank, say a 125 scf. If you plan to weld often and can handle a tank in excess of 100 pounds, then the next size up, a 250 scf, would be a better choice.
Purchasing a tank could be attractive, especially if you can find one used that is still within its tested time period. If that isn't an option, several sources sell them online, usually shipped empty. You will have to pay for shipping, but it will still be cheaper than buying one from a welding supplier, if they even sell tanks outright. Welding suppliers make their money from leasing tanks, so that is their preferred offering.
Leasing may seem a simple solution. After all, you pay the lease yearly and pay for the gas when you exchange the empty cylinder for a fully charged one. That may make sense if you don't want the hassle of keeping cylinders tested and can pass on the cost of leasing to your customers, but for a hobbyist it might be best to own rather than lease. The lease costs could pay for a new cylinder within a few years.
That said, if you buy a new cylinder and exchange it for a full one, you will essentially be giving away your new one for a used one. You could request that your new cylinder be filled and returned to you, though, if you are willing to wait a few weeks for the transportation and filling turnaround. That might be a problem if you only have one cylinder and are in the middle of a project when your cylinder goes dry.
Purchasing two new cylinders might make economic sense in the long run, as well as give you the convenience of an immediate auxiliary gas source. You could run on the second cylinder while the empty one is being returned for filling. When you get it back it can become the backup cylinder and you can rotate them indefinitely without any downtime, and with more flexibility on when you take the empty to town if you live in a rural setting.
It might be tempting to purchase two 125 scf tanks due to their lighter weight, but the best value in filling would rest with the larger tanks, say the 250 scf one. Most welding gas suppliers provide substantial discounts for filling larger bottles, simply because it takes just as much time and effort to fill a small one as a large one. You will save money by going larger, both in filling costs and initial tank cost. The 250 scf tank is only 15% higher in price vs the 125 scf tank, and you get a 100% increase in capacity.
Handling the larger tank might be challenging, especially if you are doing it by yourself. That is where a gas tank lifting device can help. The Strong Hands Gas Grabber can give you firm control and best positioning for lifting a heavy cylinder without endangering your back muscles. It also allows easy two-person lifting.
Finally, be sure to check the carrying capacity of your welding cart, both in terms of weight and cylinder diameter. The 250 scf tank is usually 9 inches in diameter and full will weigh about 130 pounds. It also extends upwards by about 56 inches, which could make your cart top heavy if your welder sits on an upper tray. A cart with low center of gravity, like the Nova 375LF, can handle up to 375 pounds and will support up to a 300 scf tank.
Whatever your choice of cart and backup cylinder storage, be sure to remove the regulator and install the protective cap on the cylinder in the following situations:
- Transporting a cylinder,
- Moving the welding cart,
- Temporarily suspending your welding activity,
- Storing cylinders, whether empty or full.
Remember that pressurized gas can propel a cylinder like a rocket motor, and a massive cylinder traveling at high speed in an uncontrolled manner is a recipe for disaster.