|04-21-2008 09:38 AM|
Agreed 100% and you have made some very good points. The flow meter you described works better for Mig/Tig welding than the pressure gauge type because it measures the actual flow regardless of pressure. That little incident with the ball hitting the top of the scale tube is not an uncommon occurrence and has been one of my pet gripes for years and sometimes it can even pop the safety plug in the top of the tube which will ruin the meter, you can not buy replacement parts. This happens when someone turns up the meter when the tank gets low on pressure and either forgets it or leaves the empty tank to be changed by someone else who is not aware it has been turned up. For the life of me I can not understand why anyone would do this but I have seen it happen countless times over the years. Doing this is just plain STUPID but people do it anyway! When a tank runs out of pressure it is EMPTY and no matter how much adjusting they do on the meter it is going to STAY EMPTY but they do it anyway! When I ran my shop I lost several Oxygen gauges and flow meters because of guys doing this and for as long as I ran the place that was the only thing I ever had to let an employee go for but one guy would do it every time he ran out of gas! Turning up the flow to the levels you would get with a wide open gauge would indeed cause porosity for the very reasons you mention and that is why I said that too much flow within reason would not hurt anything. An example of what I was talking about would be using 20 PSI (on a pressure type) when 15 PSI is all that MAY be needed, the extra 5 PSI would not hurt a thing but it would waste gas. The point you made about the air contaminating the shielding gas flow is a good one because that is probably 90% of most Mig/Tig problems. It is a common myth that turning up the flow is necessary to solve problems with a draft ruining the weld and indeed you can even find this recommendation in lots of welding books but in fact it rarely helps much. The common misconception is that the draft "blows away" the shielding gas when actually this is not the case since it would take a LOT of wind to do that. What actually happens is that the gas will become contaminated by the air when exposed to a draft and even though the gas still surrounds the weld area it can no longer protect it so the solution is to remove the draft, turning up the flow simply uses more gas which will still be contaminated. Other problems related to this can be things like a dirty or distorted nozzle which can cause a turbulent gas flow that will cause air to become mixed with the shielding gas or a leaking seal at the back of the nozzle (this can happen with either the slip on or screw on type) which will let air siphon into the gas flow. The dirty/distorted nozzle or leaking nozzle to gun seal are common problems often mistaken for draft problems and because of the siphon effect turning up the gas flow can actually make the problem worse.
|04-21-2008 01:06 AM|
ive had problems from the pressure being to high. one of our "new guys" at work opened the bottle with the flow adjustment on the regulator. that lil ball in the glass site gauge bounced off the top with a solid thud ...
i didn't realize this till i had started to lay a bead in one of those "impossible to get to with a grinder" type spots
IIRC to much flow will suck air into the shielding glass from around the edge of the nozzle, diluting the shielding gas and causing porosity, just like the venturi in a carb sucks fuel into the air stream
a properly setup mig welder should be able to lay a porosity free bead even with a light breeze blowing across the work piece. if the smallest movement of air causes porosity examine the entire sheilding gas system for problems, THEN play with the pressure / flow settings
|04-20-2008 11:21 PM|
|oldred||First off I don't recommend anyone attempt to take apart and repair a regulator because it's just plain dangerous considering the pressures you are dealing with. , now having said that if yours seems to be working ok this time then it will probably be safe enough. If the regulator fits the tank you are using then there is no reason you cannot continue to use it for either gas it is just that each will flow at a sighty different rate for a given pressure setting. This really does not matter much and instead of using a PSI setting the better way to adjust the gauge would be to turn down the gas flow while welding (on a piece of scrap!) until you start to get porosity in the weld, you will easily see when the gas gets too low, and then turn it back up until the weld is sound again then add a couple of PSI. Trying to use a certain PSI setting can waste a lot of your gas since it is the flow you are concerned about not the pressure. At any given pressure the flow could be quite a bit higher or lower from one welder to the next depending on equipment being used, what pressure setting gives the right flow for one welder may or may not work OK for another one. Setting the gas flow using the method I described will give you the correct flow no matter which gas you may be using and it very well could save you a lot of wasted gas. Having the gas flow set too low obviously can cause a lot of problems and too high, while it will not hurt the weld, (within reason of course) can waste a LOT of gas.|
|04-20-2008 09:58 PM|
Is there a difference in Argon or Co2 regulators? Am I gonna have trouble?
I have a 110 MIG with a bottle attachment I bought used. I have used it for a couple of years, but the regulator started leaking. I called around and found out I might have the wrong one and a new one would be over $80. The pressure goes up to 70psi, but I run it about 20 psi. There are two scales one for CO2 and one for Argon. Sounds to me like its a combination valve, but I don't know much about them.
I use an Argon/CO2 mix. I get the bottles at Northern Tool since that's what was on it when I got it.
I decided I would take apart the regulator and see what was up. I found a couple of O-rings were gummy and a tear in one. For about a buck, I replaced the O rings with some I found at a hardware store and it seems to be working fine now.
So my question is, does it make any difference which regulator is used? What made the o-rings gummy like that? I used some silicone grease to lightly lub the new rings before I put it all back together.