Why Simple Orifices Installed at Wire Feeder Gas Inlet Don't Work! See Video Summary

Attempts to solve start gas surge problems with an orifice mounted at the wire feeder are frequently rejected by welders since they produce unacceptable results.  Not understanding the relatively complex cause of these issues has frustrated welding foreman and welding engineers to blame welder attitude - when the welder was probably right!

Use of Fixed Orifice to Limit Surge Flow

A simple surge flow restriction orifice can be added to the wire feeder to limit high gas surge at the weld start. (We have measured surge peaks over 250 CFH in some applications which is much higher than the level needed to avoid excess turbulence!)  On the surface sounds like a reasonable way to limit peak flow, but it creates other problems!  The restrictor is typically implemented in one of two ways:

The surge limiting orifice can be sized to limit peak flow while still controlling the steady state flow at the gas cylinder with a regulator/flowmeter or regulator flowgauge or at a pipeline gas supply drop using a flowmeter. 

a. Properly sized this can work to reduce the undesirable effects of gas surge and improve weld start quality. However even if sized correctly (we find most are not) when welding stops, gas still builds in the delivery hose from gas supply to feeder.  Significant gas is still wasted when welding starts (and the pressure in the hose reduces to the ~4 to 6 psi needed to flow the steady state setting!)  However rather than exit in a very short time with a high gas surge rate it flows at higher than the steady state setting until the excess gas stored in the delivery hose is gone!  Almost the same amount of gas waste still occurs it just takes somewhat longer and is less obvious!

    It requires an understanding of why the surge existed in the first place (which is the increase in gas delivery hose pressure when welding stops and reduction to that needed to flow the steady state flow setting when it starts) to see that adding a surge orifice did not change the cause!  Many folks selling these devices just demonstrate the reduced surge velocity and conclude your saving gas waste!

b. We often find the orifice size selected to limit peak surge flow is set too low to fully purge the weld start area of moisture laden air.  The high flow surge that caused start problems is eliminated but moisture laden air is still in the start area and causes similar weld start quality problems!  Stauffer in his 1982 patent clearly defined this need for this extra start gas, See what Stauffer said.  Welders often can see this lack of extra start gas problem by observing poor starts.  They  counter by drilling out the orifice to “get more gas.”  Unfortunately the smallest drill readily available in a drill set in 1/16 inches--way to big!! 

Another way an orifice is implemented is to select a size that not only controls peak start surge flow but also sets the steady state flow rate.  The orifice is mounted at the gas inlet to a wire feeder.  Surge is reduced however with this approach there is not enough extra gas at the weld start which creates a greater  problem (defined in (b) above.)  See a production example below of this problem solved with our GSS. 

In attempt to compensate for the lack of sufficient extra start gas, the steady state flow rate may be set much higher than needed.  Gas waste from the start surge is reduced but the overall gas flow rate is set higher than needed, wasting gas! In addition to insufficient gas at the weld start to purge the weld start area, torch nozzle, etc (often causing welders to drill out the added orifice.)

Note, if a flow control orifice is used at the pipeline gas drop to set gas flow and conventional gas delivery hose is employed significant excessive gas waste and inferior weld starts occurs.  Our GSS can save 80% of that waste and improve weld start quality.  The GSS  works fine with flow control orifices placed at the pipeline drop if the pipeline pressure is consistent and the orifice properly sized.

CHECK OUT OUR "ORIFICE ASSEMBLY" THAT ALLOWS  OPTIMIZING FLOW BY CHANGING ORIFICE SIZE.

Production Example of Lack of Extra Start Gas

If sufficient shielding gas is not provided at the start, welders may try to compensate by using higher overall gas flow.  A bar joist manufacturer was using flow control orifices mounted at the wire feeders.  Argon/CO₂ shielding gas is supplied in a pipeline through about 15 feet of gas delivery hose.  The flow control orifice established the flow at 45 CFH.  However the welders wanted higher flow rates with some even drilling out the orifice!  The welding engineer wanted to avoid wasting shielding gas. With this flow setting arrangement where control is mounted at the feeder next to the gas solenoid  there is insufficient extra gas provided at the weld start.  This lack of extra gas prevents proper purging the weld start  area of moisture laden air.  

Tests were made to check weld performance and potential shielding gas savings using two cylinders of  gas on two adjacent welders instead of from their pipeline gas supply.  One welder was set with their standard flow control orifice system and a regulator providing a pressure that matched their pipeline pressure, 50 psi.  The other with a regulator/flowmeter (also of a 50 psi design) using the same 15  foot length gas delivery hose GSS without their flow control orifice.  Both steady state flows were set at their normal 45 CFH.  Since welders stand side by side, it was easy to observe the weld start quality!   Instantly the welder using the GSS noticed  improved  starting.  After about an hour with observably better results with  the  GSS welder  the  welding engineer suggested we lower its shielding gas flow  to 35 CFH!  The same improved weld start quality was observed and the welder was "happy."  In fact even though we lowered the steady-state flow to 35 CFH there was still about the same controlled amount of extra gas available at the start (that stored in the GSS hose when welding stopped.) The higher start gas flow rate established by the surge flow orifice in the GSS maintained the higher flow for a short time at the start.   This higher start flow rate quickly flooded and purged the weld start area of moisture laden air.  It was this air that was casing excess spatter and lack of start shielding on all their other welders! After about 4 hours of observation it was obvious the spatter at the weld start was less with the GSS.  We also measured a reduced use of shielding gas of 25%.   After several months of testing to check this one system during windy days etc, this shop now has GSS's installed on all 50 welders!   Bottom Line - - "Some extra gas flow at the start is very beneficial."  In addition, after about a year of use their gas supplier called to see if their business had turned down since they were using about 30% less gas- it had not!

Note: Any flow control device installed right at the feeder, be it an orifice flow control or a flowmeter will have the same lack of sufficient initial shielding gas to purge the weld start area.

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