The function of so-called gas savers is to reduce or eliminate the puff of gas that always occurs when you start MAG-welding. The puff of gas is an unnecessary loss of gas, because it occurs at much higher gas flow rate than normally used. The question is - are today's gas savers really effective – how much can you “save” by using them?
Experiment: with or without gas savers?
To find it out, we made a test with different gas savers. It comprised the most common models available at the Swedish market today: Regula (Regula SYSTEMS), Optimator (GasIQ, former Elga) and Weldflow (AGA). Test welds were made by MAG welding in position PA (bead-on-plate in horizontal position).
Welding was carried out in a welding robot to give the same welding cycle in all cases. The welding cycle contained a total of fourteen welds, in which the longest was about one minute and the shortest about ten seconds.
On the figure you can see the examples of flow characteristics for the three tested gas savers during welding, compared with a case without gas saver (cyan line).
How much gas can you save?
- All tested gas savers effectively remove the "puff of gas" at the beginning of the process.
A smaller saving was obtained when ending the welding cycle.
- All tested gas savers give a much slower increase of gas flow during the start up process, compared to the welds without gas savers.
The saving varies depending on the welding situation. Short weld times are more favourable than long, because the puff of gas that is saved appears at the beginning of the welding cycle.
On the figure you can see that with gas savers the “saving” of shielding gas is 25-35% during 12 seconds of welding time. If problems with porosity occur at the start, the “pre flow” of the shielding gas before the arc ignites has to be increased.
If we take the example above and assume that you need to reach 15 l / min in flow of shielding gas before the arc lights (to avoid start-pores), it means that “pre flow” without gas savers is 0.7 sec. and for different gas savers between 2.7 to 4.5 sec. It leads to that "savings" in the shielding gas flow drops from the previous values down to 12-16%. Welding many short welds gives the greatest savings potential, but increasing the “pre flow” gives the greatest negative effect on the welding time.
The differences between gas savers are not very big at the arc time more than 30 seconds. Savings at 30 seconds of arc time is around 20%. Long arc time is less influenced by a possible increase in “pre flow”, but any saving in gas consumption per weld is also reduced.
Depending on the welding situation you can save different amount of shielding gas. Using gas savers when welding with very short welding times, e.g. during 5 seconds, can lead to quality problems and start porosity. If the welding time is longer than about 60 seconds, the savings are less than 10%, which is within the margin of error. Gas savers are the most effective during10-60 seconds of welding.
Assume that the welding time is 20 seconds, then the savings in gas is about 25%. In normal situations the welding gas cost is less than 5% of the total welding cost. Theoretically, the saving will therefore be 1.25% of the total welding cost.
Other saving possibilities
Various economic forecasts, case studies and sensitivity calculations show that there are other areas that can be much more profitable to look at. The savings can be much greater at a process optimization, perhaps up to 25-75% of the total welding cost.
With process optimization you can choose to work in four main areas;
- Reduce the amount of weld metal
- Reduce arc time
- Reduce arc time and handling time
- Do not waste the energy and filler material (wire + gas)