January 10, 2006
Torches, cables, and cooling are three integral components in gas metal arc welding (GMAW) and gas tungsten arc welding (GTAW) equipment, and two cooling methods – air and water – are used in their cooling systems. Although GMAW and GTAW are different processes, the advantages and disadvantages of water- and air-cooled systems are the same. For that reason, you should consider similar factors when choosing a GMAW or GTAW system.
You may know that air and water are two of the four astrological elements, but you may not know just how much they can affect your welding performance.
Torches, cables, and cooling are three integral components in gas metal arc welding (GMAW) and gas tungsten arc welding (GTAW) equipment, and two cooling methods—air and water—are used in their cooling systems. Cooling prevents the power cable, torch or gun, and consumables from overheating and protects the welding operator from injury.
Although GMAW and GTAW are different processes, the advantages and disadvantages of water- and air-cooled systems are the same for both of them. For that reason, you should consider the same factors when choosing a GMAW or GTAW system:
Air-cooled guns and torches use ambient air and shielding gas to dissipate excess heat. The power cable on an air-cooled torch contains more copper than the cable on a water-cooled torch to help prevent the cable insulation from melting or possibly burning. Less copper in a water-cooled system results in a greater resistance and welding voltage drop in the cable. Air-cooled systems don't require an independent radiator cooling system or extra hoses associated with water-cooled systems.
Water-cooled systems require a radiator cooling system, which circulates water, ambient air, and shielding gas to dissipate heat from the torch or gun.
Cost. Water-cooled torches and guns require a higher initial investment because they require a separate radiator cooling system in addition to the power source. Water-cooled torches and guns also have higher operating and maintenance costs. Specially treated coolant solution, rather than tap water, is necessary for a radiator cooling system because tap water can cause algae growth or scale (mineral buildup) on the internal torch surfaces and cable assembly. In addition, water leaks from hoses and the torch neck or heads may occur, requiring immediate repair to prevent weld discontinuities.
Depending on your needs, the higher cost of a water-cooled gun or torch may be a viable investment. The flexible cable, lighter weight, and smaller size of a water-cooled system can provide more operator comfort when compared to the similar-amperage air-cooled gun or torch, which contains more copper in its power cable to help protect the cable insulation. For example, the average 250-amp, water-cooled GTAW torch weighs approximately 3 ounces and is about 6.5 inches long, while a 150-amp, air-cooled GTAW torch weighs around 6 oz. and is about 7.75 in. long. If you're welding for an extended period of time, a heavier air-cooled torch may increase your fatigue and cause downtime for cooling.
Lower consumables cost is an advantage of a water-cooled torch. The radiator cooling system allows the tip, nozzle, and/or diffusers to run cooler than with an air-cooled torch, so consumables typically will last longer on water-cooled guns and torches, helping reduce downtime associated with consumable changeovers.
But an air-cooled gun or torch also provides several advantages. For example, it works well on lower-amperage applications and, in many cases, can meet the demands of most industrial applications while still providing the same performance at a fraction of the operating and maintenance costs.
Work Site Location. When choosing between air- and water-cooled guns or torches, also consider the location of the work site. Will you be welding in a shop or in the field? Air-cooled guns and torches are more practical for outdoor work sites because they require fewer parts. This simplifies transport, setup procedures, and parts management.
Water-cooled guns and torches generally are better-suited for shop use. They're available in high- and low-amp options but require a separate cooling system. The water-cooling system and extra hoses make these torches and guns less portable.
Duty Cycle. Duty cycle (the percentage of time in a 10-minute period that the torch can be operated at a specific output without overloading) is another consideration. For example, to gas metal arc-weld 16-gauge mild steel, you need at least 160 amps with 100 percent CO2 shielding gas. If your torch is rated at 150 amps and you operate it above this amperage, duty cycle and welding efficiency will decline. Operating a torch beyond the manufacturer's rated capacity has a detrimental effect on consumables and decreases the torch life. As a result, downtime will increase because consumables changeovers will be more frequent.
Amperage Requirements. Both air-cooled GMAW guns and GTAW torches come in a variety of amperages for different applications. Air-cooled GTAW torches generally are suitable for applications equal to or less than 200 amps, but you also can find air-cooled GTAW torches in 50- and 300- amp models. Air-cooled GMAW guns come in a range of amperages between 150 and 600.
Water-cooled GMAW guns generally come in 300- to 600-amp models, while water-cooled GTAW torches usually are rated between 250 and 500 amps.
If your welding application requires amperages higher than what the gun or torch is rated, you should buy a higher-amperage gun or torch that can operate at a higher duty cycle. Both air- and water-cooled torches and guns are available up to 600 amps. On high-amperage GMAW applications (450 to 600 amps), choosing between a water- and air-cooled torch or gun depends on operator preference and cost. As a rule of thumb, for GTAW, use a water-cooled torch for jobs that are 300 amps or more in the shop. Some manufacturers also offer 300-amp, air-cooled GTAW torches for field welding.
Choosing between water- and air-cooled equipment comes down to your requirements for cost, location, duty cycle, amps, and operator comfort. Both air- and water-cooled torches and guns perform similarly when used correctly. Weighing identical variables when investigating these systems will help you determine which equipment will help you optimize your welding performance.
Mike Sammons is business development manager for Weldcraft, 2741 N. Roemer Road, Appleton, WI 54911, 800-752-7620 or 818-846-8181, fax 818-845-1542, www.weldcraft.com.
Bill Giese is product and engineering manager for Bernard, 449 W. Corning Road, P.O. Box 667, Beecher, IL 60401, 708-946-2281, fax 708-946-6726, www.bernardwelds.com.
Practical Welding Today® was created to fill a void in the industry for hands-on information, real-world applications, and down-to-earth advice for welders. No other welding magazine fills the need for this kind of practical information. Subscriptions are free to qualified welding professionals in North America.