by Michael Ouellette
Many factors go into deciding between water-cooled and gas-cooled welding torches
The amount of choice available for a manufacturer deciding on which technology best suits their needs can be intimidating. First off, the cost of any new industrial system makes every decision important. But the cost of a system is actually one of the least important factors.
When it comes to deciding between water-cooled and gas-cooled welding torches, the first thing you need to look at is the material being welded. And don’t just look at tomorrow’s entry in the schedule. Try to forecast what your customers will ask of you in the future and aim for a system that will best handle your shop’s future growth—and that of your customers as well.
Process first
If all you do is manually weld steel, then gas-cooled welding is likely your best option. It takes up less space and the heat build-up between the material and the gun isn’t severe. According to Gerhard Ofner, welding system technician for Fronius’ Perfect Welding division in Mississauga, Ont., it’s when you start welding other materials, such as aluminum, when water-cooled starts to become a priority.
“In North America gas-cooled welding is more common, but a lot of companies are switching to aluminum, and when you weld aluminum you don’t have any choice, it’s always water cooled,” he says, adding that Fronius has many customers in automotive, and probably 90 per cent of the systems it sells to these automotive companies are water-cooled systems.
“When you weld aluminum, the heat dissipates faster so you have to use more energy to melt the material, and you then need to get rid of this additional heat somehow,” says Ofner. This extra heat wreaks havoc on the contact tip and all the wear parts of a torch, as well as the torch neck itself.
If you perform this kind of welding with a gas-cooled system, you will encounter numerous problems with weld quality, but that’s just the beginning of your troubles. The heat will eventually fatigue the contact tip, requiring changeouts at a higher interval than if the gun was actively cooled. It’s also a matter of friction. When metal gets hotter, aluminum wire and copper contact tips experience more friction, which makes welding harder and impacts the consistency of the seam. And that’s the same for hand-held systems or automated systems.
When it comes to manual steel welding, you often can run gas-cooled torches without much thought.
“When you compare robotic systems to manual systems to weld steel, and you weld at say 300 amps, water-cooled automated systems can save a lot of wear part costs—the tips and everything lasts longer because the torch neck is always the same temperature. You don’t have to switch the parts as often,” says Ofner.
Smaller shops benefit
When it comes to small shops, again the first factor to consider is material. As long as you weld steel, there won’t be many advantages gained from using water-cooled guns. But as soon as you have to MIG weld aluminum, and you are in a range of 200-250 amps, water-cooled systems are your only choice.
But the next major factor for a shop to consider is the expected duty cycle of your new welding equipment. And even when it comes to the smaller companies, duty cycle is a big topic.
If you don’t need 100 per cent duty cycle—meaning the gun can weld constantly—gas-cooled systems will suffice.
To decide this, take a look at how your welders work. Are they doing smaller repair-type welds of about two inches each? Do they spend about four minutes welding and then spend the next few minutes preparing parts for the next weld? If so, then you always have the choice to go for a gas cooled. “But even in manual welding, if your welders don’t stop often in a ten minute cycle, then it’s very important to consider switching to water-cooled systems,” says Ofner. “When you need 100 per cent duty cycle, you have to go with water-cooled.”
This is especially true when it comes to high deposition welding. Fronius counts a number of agricultural vehicle manufacturers among its customer base. Even though these companies almost exclusively weld steel, it tends to be very thick steel. Thus, they need to deposit more wire in each weld, requiring more heat to melt the fill material, meaning they always opt for water-cooled systems.
Return on investment
In the long run, there must be a reasonable return on investment for any capital equipment investment. If you shop welds for just a portion of the day, gas-cooled is likely the right option. But if you notice your welders are starting to go through contact tips and torch necks more frequently, this might be a sign you need a water-cooled system. Even though these systems carry higher initial costs, the cost of consumables and wear parts could over time end up costing you more than the extra cost for the water-cooled system, especially with the price of copper and other metals increasing.
Welding wear parts such as tips and necks last longer with water-cooled systems. Spatter from the weld won’t stick on cold parts but will certainly gum up and clog tips without heat dissipation. And when these parts start to heat up, they fatigue.
“Water-cooled torch necks last longer compared to a gas-cooled torch neck because, with water-cooled systems, these parts stay the same temperature,” says Ofner.
Another reason to consider water-cooled systems is when a part is already hot, it reflects the heat back at the weld torch neck. With gas-cooled, you have to give the neck a break to reduce fatigue on the part. But it’s also a safety hazard. With a water-cooled torch, you can touch the neck and won’t burn yourself or an unlucky co-worker who strayed too close to your workstation.
Lastly, weld quality is an issue to consider in this decision. Certainly, water-cooled technology and air-cooled technology are both very capable of producing equally high-quality welds. But the key here is consistency, especially when it comes to a MIG process wire feed speed. Ofner says it helps when the torch and the tip is water-cooled because this gives a consistent wire feed speed. When these parts heat up, the wire will feed through the system at inconsistent speeds, hampering weld quality.
Disadvantages
As with any industrial technology, there are always some disadvantages. Obviously, water-cooled welding technology comes with higher initial price tag. Also, there are more parts involved, which means more chances for breakdowns and repairs. Water pumps can start leaking or fans malfunction and must be replaced. Companies like Fronius that engineer and design water-cooled systems compensate for this by using very high performance pumps. They are very small and create as little noise as possible, and they last about 30,000 hours.
When it comes to manual welding with a water-cooled system, the welder will have to contend with this noisy pump and fan. Some welders won’t be bothered by this, but if your welder is accustomed to welding stainless steel using a TIG system—a very quiet process—they definitely won’t be used to the noise created by a water-cooled system.
Lastly, there is always maintenance required. Gas-cooled systems need almost no maintenance, but water-cooled technology must be frequently checked for anything in a state of disrepair. You also have to manage the coolant, so water-cooled needs a little more attention than air-cooled. SMT
