The Power Tank, from Advanced Air Systems, is a compressed CO2 tank with a regulator, hose and fittings that makes the power of an air compressor available virtually anywhere. Ranging from 21- to 30-in. high and either 5.2- or 6.9-in. in diameter, and weighing half as much as a steel tank or aluminum scuba tank, the Power Tank can be easily carried wherever it is needed. Because the CO2 is stored in liquid form, a Power Tank packs three times the energy of the same size nitrogen tank, and the 10-lb Power Tank stores 20 times the energy of a 5-gallon air tank filled to 125 psi. Power Tank can be schlepped around pits and shared by friends, while a full-size steel nitrogen tank is probably going to stay right where it is set up the first time. With Power Tank, one can air up tires and run air tools in the pits at the racetrack, in the woods, in your own backyard or even in a junkyard. Carbon dioxide gas contains some water vapor, but usually no more than is present in the atmosphere, and will have no adverse effect on properly lubricated air tools.
Power Tank is better for intermittent uses such as filling tires or running an impact wrench than it is for continuous uses such as powering a grinder or sander. This is because the change from liquid to gas requires a lot of energy (like boiling water), and if no heat flows in, the temperature will drop rapidly. In cool or humid weather, continuous use of the Power Tank will result in condensation, or even frost, on the outside of the regulator.
Power Tank is safe if used carefully. Pressure in the tank is the vapor pressure of CO2 at the temperature inside the tank, usually between 500 and 1,000 psi, while the tank is rated for service to 1,800 psi and a maximum over 3,000 psi. A safety valve is built in to relieve pressure if it ever reaches 3,000 psi, such as if it were crushed or in a fire. If, in handling Power Tank, CO2 gas will be released directly to the atmosphere, it is a good idea to use thick leather gloves to protect one's hands. Also, be sure the tank valve is protected during storage and transport, even when the tank is empty. The system comes with a carrying handle that protects the valve and regulator assembly, while two-tank systems include a mounting bracket to store the second tank securely. All components are available separately.
I changed the quick-release fittings that came with Power Tank to standardize with what was already in use on my and my friends' air tools, using U.S.-made Amflo connectors. Note that there are several standard designs for air fittings and most are incompatible with each other, even if they come from the same manufacturer. I also bought another air hose. The compact, self-coiling hose that comes with Power Tank is convenient, but I wanted one that won't tug on my tools while I use them.
Finding a reliable arrangement to fill the tanks is important. Almost any welding shop, beverage supply firm or compressed gas outlet can fill them or have them filled. Be sure to check that you received a complete fill, though, as the amount of CO2 in the tank can be determined only by weight, not by pressure. Advanced Air Systems sells the regulator, handle and hose as a kit for those who find it more convenient to swap out tanks on an exchange basis with a gas supplier. The Ultimate Power System adds a second tank to the basic system, so there can always be a full tank waiting in the wings when a tank is emptied. Power Tank is available with 5-, 10- or 15-lb capacity. Advanced Air Systems sent us one each of the 10- and 15-lb tanks to try. We say go for the 15-lb system, as the increase in capacity versus the 10-lb tank is greater than the increase in size and weight.
