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what is this union called?

luke2152 - 5/6/14 at 03:03 PM

Have gas leaking from my mig welder - the union is not holding the plastic hose properly.
Anyone know what the union is called and where I can buy one (preferably online).
Cheers.

Dick - 5/6/14 at 03:08 PM

Pull the pipe out and cut 1/2 inch off and push back in works 9 times out of 10

Slimy38 - 5/6/14 at 03:22 PM

quote:
Originally posted by Dick
Pull the pipe out and cut 1/2 inch off and push back in works 9 times out of 10

Yep, what he said. The leak isn't necessarily the union being faulty, it's the pipe not fitted correctly. I had the same leak on mine, never found anywhere that did the union separately, but redid the connection and it worked fine. Make sure you cut the pipe square, get rid of any pipe that is damaged or scratched, and make sure it goes right in there.

What's the blue stuff on the pipe though, that doesn't look right? Have you tried sealing it with something?

Jamesc - 5/6/14 at 03:26 PM

Is it definitely that part of the fitting?

I had the same thing recently and it turned out to be the actual screw in part not fitted properly. I wrapped some PTFE tape around the thread and tightened it up, no problems since!

rayward - 5/6/14 at 03:35 PM

thats a push fit pneumatic connector , if know what pipe and thread size it is , i will probably have one if you need it

Ray

luke2152 - 5/6/14 at 03:52 PM

I'm pretty sure - its not push fit - certainly not like the quick couplings on air and hydraulic hoses. Seems to me the blue metal bit is a sleeve that grips the hose but not anymore. I think its a union you use once because the blue inner is pretty well stuck in the outer and the hose is still loose. I will try trimming it down but with a loose hose I don't think it is just due to the end being rough.

And yes well spotted I put a bit of hymolar around it to try and seal it unsucessfully. I should add that it only leaks when the gun is twisted one way to put it under tension and it definitely leaks out the hose - not the threads

Slimy38 - 5/6/14 at 04:18 PM

The blue part being loose is a sure sign that the pipe hasn't been fitted correctly. The blue part seems to have 'teeth' that grip on the pipe as it's pushed in. If you remove the plastic pipe you'll see where it's gripping as it'll leave tiny scars.

When you remove the plastic pipe the blue collar should move in and out about a millimetre or so. When the pipe is installed it goes solid. I did 'help' mine a little bit and held it out of the metal section as I pushed the pipe in. I think it meant it gripped higher on the plastic pipe and then could seal against the union inside a little better, but that could just be my imagination.

Having said that, if the collar is stuck in the outer then perhaps yes it is a bit beyond just having clean pipe installed, it may actually be damaged.

[Edited on 5/6/14 by Slimy38]

luke2152 - 5/6/14 at 06:20 PM

quote:
Originally posted by Slimy38
The blue part being loose is a sure sign that the pipe hasn't been fitted correctly. The blue part seems to have 'teeth' that grip on the pipe as it's pushed in. If you remove the plastic pipe you'll see where it's gripping as it'll leave tiny scars.

When you remove the plastic pipe the blue collar should move in and out about a millimetre or so. When the pipe is installed it goes solid. I did 'help' mine a little bit and held it out of the metal section as I pushed the pipe in. I think it meant it gripped higher on the plastic pipe and then could seal against the union inside a little better, but that could just be my imagination.

Having said that, if the collar is stuck in the outer then perhaps yes it is a bit beyond just having clean pipe installed, it may actually be damaged.

[Edited on 5/6/14 by Slimy38]

Blue part is definitely not loose but pipe is. Have trimmed the pipe and it still won't hold it. I will try to measure the thread tomorrow and look for another

daviep - 5/6/14 at 08:48 PM

As per the replies above it looks like a normal pneumatic push fit connector, commonly know as "prestolok" or "push lock" or "push fit". You need to know the pipe size (beware the imperial and metric are different) and thread size.

Are you 100% sure the pipe is pushed fully home, sometimes they need a good shove to get the pipe through the o ring, also cut the pipe with a knife as opposed to side cutters or pliers to avoid flattening the tube when cutting.

Cheers
Davie

luke2152 - 28/6/14 at 09:44 AM

for those interested the hymolar didn't work initially but couple of weeks on it is working perfectly

alfas - 28/6/14 at 02:26 PM

thats a standard push fit pneumatic connector.

the blue ring is only for removing the hose:

you push it in for unlocking the internal "grippers" and in the same time you need to pull on the tube.

very important is:

the tube needs to be cut absolutely straight at its end. the tube needs to have a difined outer diamter (the corrosponing diamter is normaly printed on the blue ring)

due to the locking system, the tube slightly suffers from being unlocked plenty of times. if this happens you shorten the tube around 10mm and it should work again.

if all fails...your connector might be faulty...which is rare.