Repairing a Copper to Steel Brazed Joint.

[Grizzly]

Hi Guys.
I had a issue the other day where.
Having identified a small "Pinhole" leak on a R22 system on it's Silver soldered pipework joint.
Where the Copper Liquid line (1-1/8") joined into the receiver Steel socket.
My problem was after 3 attempts at sealing this joint.
Where each time the leak moved around the pipe circumference!
When explaining the problem to the customer.
He was not surprised as a previous company had, had a similar problem.
Where they resorted to replacing the pipe stub and elbow above it.

Basically that is what I ended up doing.
Guess what as soon as I put rod to joint the braze flowed beautifully around the joint!

My question is has anyone experienced similar before?
Where no-matter how careful you are a joint refuses to flow.
The old joint did appear to lack "penetration" and the braze seemed to have sat around the lip of the socket!

Surely it's not just me?
Grizzly

[monkey spanners]

I've seen something similar a few times when brazing into old systems, i have a theory that the heat of brazing burns some wax or other crap from inside the pipe and it comes out the joint as smoke leaving a coating in the joint that even flux won't help with.
I think i ended up pulling the pipes apart and cleaning them up with a file and that abrassive strip before trying again.
Must admit to not using ofn when this has happened....

Another time was when my old boss had sold a old glycol slush milk cooler as a dx and i had to braze copper to stainless, eneded up getting my mate to run the vac pump to suck the braze in :rolleyes: :D

Jon

[chemi-cool]

Mr. Grizzly,

A few steps and you are behind that problem.

1. Always use high quality silver rods http://www.eutectic.co.uk/wCastolin_uk/index.php

2. Heat the connection point till the steel start to get red and pull out the old copper tube.
3. Cut one mm of the steel pipe so the edge is shinning and clean.
4. There is one little thing about the soldering flame, for copper you need extra oxygen and for steel extra gas, so make sure your flame is neutral.
5. Heat the steel carefully and apply silver on the inside for a depth of 10mm.
6. Cut a new piece of copper tube and coat the end of it with silver.
7. Now place the coated copper tube at the opening of the steel pipe and heat the outside of it slowly till the silver melts and the hot copper tube slides in.
8. Let it cool for a bit to prevent the carbon in the steel forming an un weldable area on the end of the steel pipe.
9. After it cooled for a minute or so. apply with a lower flame silver on the edge of the steel pipe, filling carefully the gap.
10. You can now, to be extra sure, add another coat but this time use your regular silifus rods 2% or 5%, whichever you use, it will make the place stronger.
11. Braze the original copper tube the end of the copper tube [6].
12. Use 40% silver rods
[the writer was teaching brazing and arc welding for 15 years];)
Still having problems? find me on Skype as chemi.cool

[Grizzly]

Thanks Chemi!
[the writer was teaching brazing and arc welding for 15 years];)
Erm I have been doing both for 39yrs!!
As you see from my post adopting what you prescribe .
I sorted the problem.

Having said that Chemi.
I have always used Eutectic rods where possible.
Absolutely Brilliant Rods, in fact I am just running out of High silver Copper to Copper rods.
That J&E Hall issued me with around 7/8 yrs ago.
(In those days you were issued with a full pack. Not the take just enough for the job attitude you get now)
Sadly I cannot identify the exact replacement.
Any ideas anyone.
These rods are a dull silver / pewter colour.
Different to the silphoss 5 or 15 rods!
M.s.
Spot on.
I suspected something like you describe happens.
That's a good interpretation of what may be happening.
Any form of impurity and your stuffed.
Yes you are correct.
I did not use Nitrogen either as a purge gas or to test the joint.
Two reasons:-
1) The system was part charged,
Approx 40kg charge. So to avoid a complete reclaim.
I pumped the system down several times.
Having shut the receiver inlet valve.
Then transfered the remaining vapour via a reclaim unit into the second system.
Which needed a "Top up!"
2) How to purge with Nitrogen when it is the Last joint?
So you can guess how fed up I was repeating all this 4 times.
One of those "It's got to be done" and your on your own jobs.
Even the site engineer left me to it!
Grizzly

[chemi-cool]

Glad to know its sorted out now.

[Toosh]

Thanks Chemi!
[the writer was teaching brazing and arc welding for 15 years];)
Erm I have been doing both for 39yrs!!
As you see from my post adopting what you prescribe .
I sorted the problem.

Having said that Chemi.
I have always used Eutectic rods where possible.
Absolutely Brilliant Rods, in fact I am just running out of High silver Copper to Copper rods.
That J&E Hall issued me with around 7/8 yrs ago.
(In those days you were issued with a full pack. Not the take just enough for the job attitude you get now)
Sadly I cannot identify the exact replacement.
Any ideas anyone.
These rods are a dull silver / pewter colour.
Different to the silphoss 5 or 15 rods!
M.s.
Spot on.
I suspected something like you describe happens.
That's a good interpretation of what may be happening.
Any form of impurity and your stuffed.
Yes you are correct.
I did not use Nitrogen either as a purge gas or to test the joint.
Two reasons:-
1) The system was part charged,
Approx 40kg charge. So to avoid a complete reclaim.
I pumped the system down several times.
Having shut the receiver inlet valve.
Then transfered the remaining vapour via a reclaim unit into the second system.
Which needed a "Top up!"
2) How to purge with Nitrogen when it is the Last joint?
So you can guess how fed up I was repeating all this 4 times.
One of those "It's got to be done" and your on your own jobs.
Even the site engineer left me to it!
Grizzly

Hi Grizzly,Another tip is to tin the copper with soft solder it works good then use a silver solder rod, it worked good for me over the years and you don`t need a lot of heat to do it.

Regards

Norm

[Grizzly]

Hi Toosh.
Sorry my reply about the Eutectic rods may have confused the issue.
That was me asking for help in identifying my original Copper to Copper rods.
Basically on the original joint I used a pre-fluxed Silver solder rod.
And again on the new joint / pipework.
As is the practise with dissimilar metal joints.
Do you mean Plumbers solder when you say soft solder Toosh?
Over here it is all Lead free now, does that make any difference to your "top tip"?
I have not heard of that one sounds interesting!
Cheers Grizzly

[monkey spanners]

I have seen a few old R12 systems put in with plumbing solder, which was fine till we put ester oil and R134a into them.

These were old milk tank systems from 40+ years ago.

[US Iceman]

The old joint did appear to lack "penetration" and the braze seemed to have sat around the lip of the socket!


That sounds like incomplete heating of the entire joint. The biggest problem I have had with a silver solder joint was one that was taken apart and re-soldered. To do this the entire joint has to be heated so that the flux melts and allows the solder to flow.

What percentage of silver did the solder have? And what type of flux did you use Grizzle.

[Magoo]

Toosh.
You are a plonka with tinned solder and copper tube. That shyte is for plumbers stuff. Not the current refrigeration practise.

[FEISTY]

Hi Grizzly. Magoo makes valid point. At least here in Chicago code requires brazing only of any refrigeration joint. Soft solder is fine in low pressure plumbing and was common in a/c work, although same refrig. high side pressures exist. It's my way of always knowing if customer had a/c tech " try and fix it cheap ". We use Stay-Silv45 and flux both sides of joint. Works almost every time...1st time. If braze rolls out the surface was still dirty. Good luck !!

[Toosh]

Toosh.
You are a plonka with tinned solder and copper tube. That shyte is for plumbers stuff. Not the current refrigeration practise.


Oh am I you missed the point the solder makes the silver eaisier to bond and have done it plenty even in NZ and the joints held,I have been out out of the business for 20 years ( due to a head on Collision) so new refrigerants and oils I don`t know about.

Norm

[Grizzly]

Sound like there is another Head on collision Pending?
Guys thank you so much.
Basically if I extract all the relevant inputs.
It would be logical to assume that
If the Braze does not flow etc.
Then it is likely Poor preparation or joint cleanliness!
In my case the original joint was not prepared properly in the first place.
Like I said originally.
The joint was good only after removing the original pipe.
Fitting new and re- preparing the joint for brazing.
Thanks Grizzly

[Steve Wright]

I've been taught not to use any phos containing rod on steel as it makes it fragile.

I it came from JW Harris (a manufacture of brazing material) however I've done what Grizzly did a bunch of times.

[cu2chat]

Soldering or Brazing clenliness of both surfaces imperative for a good joint. my question would have been why did joint pin hole again so soon? and is steel socket on receiver corroding from the inside