[Markus]

Read some article about welding ferritic stainless steels and noticed this picture. Propably nothing new, but decided to share it as a good reminder at least

[Superiorwelding]

Markus,
You wouldn't be applying that we need to resurrect that topic again would you?
Good demonstration in that picture for sure.
-Jonathan

[Mongol]

Markus,
You wouldn't be applying that we need to resurrect that topic again would you?
Good demonstration in that picture for sure.
-Jonathan

Implying.....Sorry, had to do it.

[TRACKRANGER]

Gas lenses are good, no doubt. I've seen those images before. My personal feeling is that there's a bit of a 'staged' set-up involved... Maybe a little bit of 'suction' going on outside the picture frame on the RH image?

[Artie F. Emm]

At the very least they'd have to manipulate something to make the gas visible. Maybe a hot humid environment so the cooler argon shows up?

[TRACKRANGER]

At the very least they'd have to manipulate something to make the gas visible. Maybe a hot humid environment so the cooler argon shows up?

I doubt very much that it's Argon in the picture. Probably connected to a smoke machine, so as to demonstrate.

But I don't believe the physics of a gas lens can change the properties of gas delivery to the significant extent shown in the image.

[dirtmidget33]

At the very least they'd have to manipulate something to make the gas visible. Maybe a hot humid environment so the cooler argon shows up?

I doubt very much that it's Argon in the picture. Probably connected to a smoke machine, so as to demonstrate.

But I don't believe the physics of a gas lens can change the properties of gas delivery to the significant extent shown in the image.

you can do this same experiment with faucet. Take a glass turn it upside down and run the water at center of the bottom of glass. Play with the pressures, to high and it bounces off the surface if adjusted lower you will get nice even coverage across the bottom of glass. like a good smooth blanket (if the faucet screen is good quality and not plugged up with debris). Mark how far you opened up the faucet. Now remove screen set it back at same pressure and compare the blanket of coverage.

If you do this you will be surprised at the difference. I used the word pressure above in reality your water pressure coming in home is a set variable the faucet controls the flow just like our flow meters do. Now certain items like a shower has nozzles that restrict that flow forcing that lower pressure and flow to shoot out higher pressure. same principle with a shower like a pressure washer wand. Remove the nozzle and pressure drops to barely nothing. Put nozzle back in and you can put a hole in your finger (don't try that please )

[TRACKRANGER]

Good suggestion, but the physical properties of a liquid are very much different to the physical properties of a gas. That needs to be taken into consideration, surely.

[Superiorwelding]

Markus,
You wouldn't be applying that we need to resurrect that topic again would you?
Good demonstration in that picture for sure.
-Jonathan

Implying.....Sorry, had to do it.

Oops
-Jonathan

[Otto Nobedder]

Good suggestion, but the physical properties of a liquid are very much different to the physical properties of a gas. That needs to be taken into consideration, surely.

No. Liquids and gasses are both fluids, and subject to the laws of fluid dynamics.

Because of different densities, the flow rate is the main variable in their behavior. In the faucet/gas lens comparison above, the water flow could be measured in liters/minute, and the gas in liters/hour, but the behavior is the same.

Notice that blimps/derigibles have similar controls that function the same way, and Penguins don't swimming, they fly under water.

Steve S

[RichardH]

I think those are marketing photos from CK, and yeah it's almost certainly smoke to show the behavior. The concept at play with a gas lens is called laminar flow - getting the molecules all flowing uniformly in the same direction.

In a regular nozzle, the gas comes out perpendicular to the electrode inside the cup, bounces around, and eventually finds its way out - but with a lot of swirling / turbulence as a result, and only in the general direction. As an effect, the turbulence can mix atmosphere into the cloud.

With a gas lens or ScotchBrite in the cup, the turbulence is thwarted, and gas "oozes" calmly out of the lens and creates an even pressure source. The front end of the cup is the only exit, and as it travels along the length of the cup it gains a uniform direction of flow, exiting as a cohesive stream. In welding, this has the added benefit of allowing really long stick-out with good gas coverage. (Which is why I wonder how effective very stubby gas lenses are, since the cup isn't long enough to give the flow much direction.)

You can see a similar effect with water, where a hose can only shoot a stream so far before it loses it's form, but the same flow through a laminar water jet looks like a glass rod most of its length. It's a pretty cool science fair experiment, actually.

Cheers,
Richard

[xwrench]

A minor quibble; probably has no bearing on this, but I thought gases can compress. Liquids, not so much.
-Eldon

[dsmabe]

You are correct, but gas needs pressure to compress. By the time the shielding gas gets to the cup, its at atmospheric pressure, gas and liquid are going to behave very similar.

[Markus]

Well this subject arouse guite much talk But that's good, I think.

I personally believe that photo, which I posted is 100% true without any tricks and it's propably done with something else than argon. Anyway it would be interesting to test that experiment and see what happens when metal is smoking hot! Temperature can make a lot of difference though.

[TRACKRANGER]

For the two photos to be accurate in demonstrating the comparative properties of a welding lens, the 'visible' gas solution used in the demonstration should have the same properties as Argon, including Density.

Argon is 38% denser than air. The photo on left does not have many indicators that the gas used has any significant density.

For accurate representation of what will really happen, the gas (smoke?) used in the photos should have the same physical properties as Argon.

Markus' comment about temperature is definitely worthy of consideration also.

My 2 cents

Ranger.

[dirtmidget33]

It all comes down to fluid dynamics. Yes the examples use a gas other then argon so you can see it but the principles of fluid dynamics and Laminar flow still apply. Depending on gas used they will be at different flow rates to achieve the same result but the gases and liquids for that matter will still blanket and react the same way Some just require a higher flow rate then others to achieve the same result. Example of that is you use a different flow rate for argon then you do helium but both gases follow the same laws of physics.

[dirtmidget33]

No matter what it is gas or liquid all a lens does is help align the molecules to travel in the same direction. if you think about a regular collet body the gas comes out a a 90 degree angle as it heads to cup wall and collides with the side of It. The gas molecules are being bashed all over the place and have no real direction as they come out of cup. Shoot a BB gun at concrete wall it comes back at you. (don't do it but same thing happens to atoms) The lens changes direction of molecules and screens help align the molecules to flow out in a parallel streams as they exit the lens.

This explains laminar flow pretty good from Wikipedia
"In fluid dynamics, laminar flow (or streamline flow) occurs when a fluid flows in parallel layers, with no disruption between the layers.[1] At low velocities, the fluid tends to flow without lateral mixing, and adjacent layers slide past one another like playing cards. There are no cross-currents perpendicular to the direction of flow, nor eddies or swirls of fluids.[2] In laminar flow, the motion of the particles of the fluid is very orderly with all particles moving in straight lines parallel to the pipe walls."

The mathematics of fluid dynamics gets complex quick. Trust the companies on this one. On another note scotchbrite pads shoved in a cup does not give the same results as screens the purpose of screens is to achieve that parallel flow. The gas molecules do not exit scotchbrite as smooth as screens. It takes several screens to help smooth out flow.

[Oscar]

Good suggestion, but the physical properties of a liquid are very much different to the physical properties of a gas. That needs to be taken into consideration, surely.

No. Liquids and gasses are both fluids, and subject to the laws of fluid dynamics.

Because of different densities, the flow rate is the main variable in their behavior. In the faucet/gas lens comparison above, the water flow could be measured in liters/minute, and the gas in liters/hour, but the behavior is the same.

Notice that blimps/derigibles have similar controls that function the same way, and Penguins don't swimming, they fly under water.

Steve S

I respectfully disagree. Both are indeed subject to the laws of fluid dynamics, but when subject to STP conditions in the atmosphere they will behave completely different. In one case (argon flowing into atmosphere), you have gas dilution into another gas (atmospheric air). Water flowing out of a faucet into atmosphere will behave completely different because you have a liquid dilution into a gas at atmospheric STP. It is not just a matter of density. Water flowing into a volume filled with gas or atmospheric air will not eventually fill the entire volume as time goes by (so long as STP conditions are sustained). Argon flowing into the same volume, however, will eventually homogeneously mix with the other gas. This is the reason argon in our atmosphere does not sink down to the ground level (or below ground). It is this homegeneous mixing of gases that separates the liquids from the gases. Hence the reason the Ideal Gas law PV = nRT is called the Ideal Gas Law, no the Ideal Fluid Law; it does not apply to all fluids (meaning liquids).

[TRACKRANGER]

Thanks Oscar

You've obviously gone into significant, researched scientific detail. Your comparisons to the differences between gas and fluid states are appreciated.

Ranger

[dsmabe]

Isn't it the turbulence in our atmosphere that keeps gasses homogeneously mixed. If there was no turbulence on earth/ in earths atmosphere, gasses should act the same as fluids of different densities. Eventually all gasses of different densities would seperate, similar to how a Italian dressing mixture will settle to different layers given enough time.
In the lack of turbulence argon would "pour" similar to liquid since it's heavier than air, and fill a volume of space. It would only mix in the presence of turbulence.

Not sure what was meant by saying "Water flowing into a volume
filled with gas or atmospheric air will not eventually fill the entire volume as time goes by. ", but last time I checked that is exactly how you would fill a cup. The cup is initially full of atmospheric gas which gets displaced by the denser water. That cup would eventually be completely filled as long as flow continued long enough.

[wheresmejumper]

I dont think anybody 'staged' anything here.why would they?
people use gas lenses because they work, ask anybody that has welded stainless..not by magic but by laminar flow as stated already.
The pic just shows how.its not there to sell a product, just to demonstrate how it works

[Markus]

I dont think anybody 'staged' anything here.why would they?
people use gas lenses because they work, ask anybody that has welded stainless..not by magic but by laminar flow as stated already.
The pic just shows how.its not there to sell a product, just to demonstrate how it works

+1 !

[Oscar]

Isn't it the turbulence in our atmosphere that keeps gasses homogeneously mixed. If there was no turbulence on earth/ in earths atmosphere, gasses should act the same as fluids of different densities. Eventually all gasses of different densities would seperate, similar to how a Italian dressing mixture will settle to different layers given enough time.
In the lack of turbulence argon would "pour" similar to liquid since it's heavier than air, and fill a volume of space. It would only mix in the presence of turbulence.

Not sure what was meant by saying "Water flowing into a volume
filled with gas or atmospheric air will not eventually fill the entire volume as time goes by. ", but last time I checked that is exactly how you would fill a cup. The cup is initially full of atmospheric gas which gets displaced by the denser water. That cup would eventually be completely filled as long as flow continued long enough.

That's the exact jist of it---at STP you cannot remove the "turbulence" because this is what separates it from a liquid here on earth. For a gas at STP the mean free speed of the atoms/molecules is significantly higher than that of what we call liquids. Remove this property of gases (turbulence as you call it), and you're no longer at STP, which is the condition that exists as pressurized argon is depressurized into our atmosphere when it flows out of the argon tank. To remove the very essence of a gas by eliminating said turbulence and you would have liquid argon (at a very very low temperature), which is not the case at all when welding.

As to filling a cup, yes the argon or any Other gas would get displaced if you filled it completely---that wasn't my point. What I was trying to get at is that if you only partially fill it (specifically meaning: partial liquid dilution into a gas), the water will not spontaneously and homogenously mix with the remaining gas (mix being the key word---and therein lies my typographical error, I said "fill" when I should have said "mix", or perhaps I should have said "fill as a homogeneous mixture).

[Otto Nobedder]

I respectfully disagree. Both are indeed subject to the laws of fluid dynamics, but...

Save the "but"... Your previous statement said it, "subject to the laws...). Reynolds numbers are Reynolds numbers, regardless of the density transition between the laminar and turbulent layers.

Laminar flow from a "flow aligner" like a gas-lens can be demonstrated regardless of the density disparity between media.

[dsmabe]

I thought that might have been a typo but wasn't sure. But as far as turbulence is concerned with the situation that we deal with, welding shop etc., turbulence can be the fan that's blowing. If the environment that a person is welding in is somewhat controlled, you can reduce or eliminate turbulence to the point where argon, being heavier than air, can act, in its gaseous state, much like a liquid. It can fill a cup just like a cup being filled with water. As long as there is no turbulence in the room (moving air) the argon in the cup wouldn't mix with the air in the room.
Especially in tig welding, effort is made to reduce or remove any wind when welding. This is to protect the argon shielding that could be disturbed or blown away by turbulence around the weld.

A cool little project to see how a gas can act just like liquid.
Place a lit candle in a deep bowl, get a large measuring cup and add some vinegar to it. Then add baking soda, this releases carbon dioxide which is heavier than air. "Pour" the carbon dioxide into the bowl with the lit candle careful not to pour out the vinegar. Once the carbon dioxide reaches the flame, the flame will extinguish. As long as there is no turbulence you can light a match, and as you try to relight the candle, the match will extinguish as you get close to the candle. This is because the carbon dioxide is behaving the way you would perceive liquid to.