I’m a Numpty

[bigfellayork]

I virtually always give things a once over before using them.
I acquired a GYS Smartmig 162 and found it wasn’t cutting the mustard. Struggling to penetrate. Welds looking rough.
I decided to change the reel of wire and decided on GYS own wire. Cheap enough and they put their name to it.
Anyway while I was fitting the reel I thought I’d give the thing a quick once over.
Although only three months old it’s only been with me a week.
Staring down at the pipe fitting I noticed the jubilee clip appeared tight but didn’t fit snugly all the way round.
I turned the gas on and could hear a very slight leak.
The connector for the hose is very slim and it looks like the clip was squeezing the pipe only 90% of its circumference.
As well as letting gas escape could it also pull air in in operation?
Cut the hose back. Fitted better suited clip.
I could be wrong and it could just be the wire change but the welder is running sweet as a nut now. Power is a lot better
Welds a lot smoother in appearance and lot better penetration.
Moral of the story check things over.
It very nearly got hurled through the workshop window out of frustration the other day.
Now I’m a happy bunny.

 

[knighty]

the gas is pressurized, so it'll push out, no air will get in

when it's sitting not getting used the gas in the pipes will slowly be replaced with air... but it should only take seconds to purge that

my guess it the gas was leaking out so not enough shielding


I've forgotten to turn the gas on a few times, and it throws the weld right off... you'd expect it just to look crap when it was done, slag etc... but nope if seams to screw with everything :-(

 

[Hood]

the gas is pressurized, so it'll push out, no air will get in

Maybe not the case, the flow of gas when it is being used may cause a vacuum and draw air in.
It is a problem I had when welding up an aluminium boat, it was driving me mad as I was getting porosity and I tried everything. In the end I found a small pinhole in the gas line and it was pulling air into the line and causing the problem.

Edit
For some reason I never saw pdg's reply before I posted. Looks like a better worded explanation than mine

 

[addjunkie]

https://en.m.wikipedia.org/wiki/Bernoulli's_principle

 

[knighty]

I've built a few venturis before

I don't think the effect really applies here - as long as gas was escaping when the welder was in use then there's no air getting in

there's too much flow restriction downstream of the gas fitting (other fittings, gas solenoid, small tube in torch hose etc.) - I don't think the pressure difference across the hose barb would be enough for the venturi effect

plus, leak was on the welder end yeah, so the leak would be before the restriction not after it, so no venturi effect - leak is at the slow high pressure area not the fast low pressure area (tho as above, I don't think pressure difference is enough to really have an effect)

 

[Hood]

I can assure you it was my issue, changed everything from Gas cylinder to wire , dried and heated the sections of Alu etc etc and only when I changed out the gas hose did it stop. I didn't think it could be the hose as I could not detect any leaks at all but after I changed it and cured the problem I fitted a plug to one end and used compressed air and a bucket of water and eventually found the tiniest of pin holes.