Gas Saver Systems being tested on gas cylinders connected to wire feeders.
Welding shops and welding schools that use the GMAW (MIG) welding process could save as much as 60 percent of the shielding gases that they purchase by using a newly patented system that recaptures gases left in delivery hoses when welding processes are stopped.
Left over shielding gases typically remain in delivery hoses when welding is stopped, and that extra gas usually is expelled when welding is restarted. That could waste as much as 25 percent to 60 percent of the gases that a shop buys.
Jerry Uttrachi, president of WA Technology and 2007 president of the American Welding Society, saw that waste, and invented a way to prevent it. Uttrachi designed, developed and patented a product he calls the Gas Saver System.
Uttrachi's system includes a custom-made hose that has an inside diameter of 0.125 in., and a surge flow-limiting orifice. The hose is made with composite fiber-reinforcements that gives it toughness in shop environments, and it has a large outside diameter. The surge flow-limiting orifice is positioned at the end of the hose that connects to the wire feeder or welding machine. Installation of the system involves removing the existing hose that delivers gas to the wire feeder or welding machine and replacing it with the system.
Saving $50,000 per year making cars
An automaker manufacturer tested the Gas Saver System at its plant in the southeastern United States, and compared it to GMAW equipment that used a cylinder of shielding gas with one of its standard shielding gas delivery hoses.
As a result of that test, the automaker installed Gas Saver Systems on 68 of its manual GMAW welding machines. Those welding machines operate with 0.035-in. diameter solid wire, and use an argon/CO2 gas mixture that is delivered to each welder through a gas manifold gas system, Uttrachi said. The manifold system uses a large diameter pipe header to ensure that uniform gas pressure is delivered to each of the flow meters. The length of hose for each of the 68 installed Gas Saver Systems varies from 70 ft. to more than 100 ft.
After the system was installed on the 68 machines, shielding gas consumption dropped by more than 30 percent for the automaker's threeshifts-per-day operation, producing a savings of more than $50,000 per year. After those units were in production for a year, the automaker added another 44 Gas Saver Systems.
At the car plant, shielding gas remained in delivery hoses when welding stopped and, each time the welding process restarted — even to make short tack welds or to inch the wire forward — the excess gas in the hoses was expelled. The amount of gas that was wasted depended on the regulator or flowmeter or pipeline pressure, and could exceed five times the hose volume when measured at standard pressure and temperature, Uttrachi said.
Additional, the high flow rate in hoses creates turbulence in the flow of the shielding gas that allows air and moisture to be pulled into the shielding gas stream. That air and moisture produce excess spatter at the start of the weld and could cause weld porosity, Uttrachi said.
Shielding gas pipeline distribution systems are designed to run at 45 psi to 65 psi to compensate for the restrictions to gas flow that occur when problems arise. The problems can be such things as twisted or pinched gas lines, or other situations that could cause the flow of gas to slow down.
When welding commences, the pressure in the delivery hose will drop to the pressure level needed to produce the appropriate flow rate — 4 psi to 6 psi — that is needed to weld. When welding is stopped, the gas in the delivery hose returns to the pressure that is in the pipeline system. That means that when a welder starts to weld again, the excess gas in the hose could flow at a surge rate in excess of 150 cu. ft. per hour. It is this high surge flow that wastes gas and pulls air and moisture into shielding gas stream, Uttrachi said.
However, a small amount of pressurized gas is needed to start a weld. It is this pressurized gas that displaces the air that entered into the torch cup, body and gas line when welding was stopped, and that provides pressurized gas to expel the air in the weld-start zone. This is why the Gas Saver System does not alter the pressure in the delivery hose. Instead, the system's built-in surge restriction orifice limits the maximum flow rate to the appropriate level for welding.
Uttrachi said a structural aluminum fabricator determined that his welding equipment set-up had shielding-gas-surge flow rates in excess of 250 cu. ft. per hour. So the fabricator tested the Gas Saver System to determine how much of its argon/helium gas mixture it could save. One gas cylinder was connected to a standard gas delivery hose, while another cylinder was set up with Uttrachi's system. The result was a savings of more than 40 percent. The fabricator then installed the device on 93 GMAW machines that it uses to weld aluminum and steel.
A slight variation
In another example, a bar joist manufacturer was using flow control orifices mounted at its wire feeders and an argon/CO2 shielding gas mixture. The gas was supplied through a pipeline and 15 ft. to 20 ft. of gas delivery hose. The flow rate was established at 45 cu. ft. per hour, but the welders wanted a higher rate to compensate for drafts in the shop, Uttrachi said. Because of the way the gas delivery system was set up, the gas pressure in the hose was always the same as the pressure in the pipeline — 50 psi. This resulted in little to no gas surge at the start of a weld, which was good. However, there was not enough gas to displace air in the weld start zone and torch.
The manufacturer installed a Gas Saver System with 20 ft. of delivery hose on a welding machine, but placed the flow-setting orifice on the end of the gas delivery hose that was connected to the gas pipeline. This arrangement produced 5 psi pressure in the hose while welding, and left the small amount of excess gas in the hose.
When welding commenced, the extra gas was expelled at a rate higher than 45 cu. ft. per hour — for a brief period — to expel the air in the weld zone and torch. However, the restrictor that is built into the Gas Saver system controlled the surge flow rate.
The welder who was using the device noticed that his weld starts had improved. He even adjusted his power source to maximize the advantage. He also noticed that his set-up produced less spatter at the weld start than did the regular setup used by the welder next to him.
Another part of the test involved reducing the gas flow rate to 35 cu. ft. per hour. This reduced gas flow rate continued to improve weld starts, Uttrachi said.
After several months of use to determine the performance of the system when drafts were encountered, the company installed systems on all 45 of its welding machines. The result was a 25 percent reduction in shielding gas consumption, Uttrachi said.
How to calculate gas waste
Determine in pounds the amount of welding wire used, and the amount of shielding gas in cubic feet purchased over the past six months.
A welding operation that purchases 46,000 lbs. of 0.045 solid wire over a six month period would multiply that quantity by the amount in the far-right column that corresponds to the wire size and type of wire purchased:
(5,000 cu. ft. ÷ 1,000 lbs.)
X 46,000 lbs.
= 230,000 cu. ft. of gas.
If the operation purchases 350,000 cu. ft. of gas, it wastes approximately 120,000 cu. ft., or 34 percent of the gas purchased.
Typically, the amount of shielding gas that is needed is estimated by multiplying the number of hours of welding by the amount of the gas flow as indicated on a flowmeter. Uttrachi said that this calculation is based on an erroneous assumption: No gas is wasted; therefore, shielding gas accounts for only about 5 percent of total welding costs.