Supporting > Boilers
3 inch boiler build
gary.a.ayres:
Hi -
I thought I should start a bespoke thread on this work in progress rather than indefinitely hijack my own 'introduce yourself' thread http://www.modelenginemaker.com/index.php/topic,8234.0.html.
Following my experience with a leaky check valve during the first hydraulic test, I followed advice from some of you and took two remedial steps: replacing the steel ball in the check valve with a nitrile one, and adding a globe valve between the pump and the check valve. This really did the trick, and the result was version 2 of my test rig which has no leaks in the water feed system. When that globe valve is closed, it's closed! Photo below.
And now the bad news: the improved system showed clearly that what I had thought was a repair was an improvement, but not a repair. The offending tube still leaks, albeit more slowly. During the test, the pressure dropped from 90 psi to 78 psi over a 30 minute period - better than it was, but a leak nonetheless. The photo below (top left tube) shows the problem - there is a gap under the fillet which I added, probably due - I think - to insufficient heat during the attempted repair. My plan is to reheat it and try to melt the solder which is already in place so that it will flow around and into the joint more than it has. The boiler is now back in some new pickle for 24 hours to get it as clean as I can prior to reheating it, hopefully tomorrow evening. I will, of course, use plenty of flux and follow the previous advice on giving the whole thing an overall background heat with propane before focusing on the flaw with oxy/mapp.
However, if anyone has any other ideas I'd be happy to hear them.
Photo below:
gary
crueby:
I had a spot like that, and wound up having to grind off the solder overhang so that I could clean the metal underneath properly, the pickle was not enough to get rid of soot/etc under there. If you have something like a Dremel rotary tool, and a small bur, that is very wuick to do. Then reflux, heat, and add a little more solder there as if it was a new joint being done - more reliable a method than hoping it will reflow.
Also, if you have more than one grade of silver solder, using one with a lower melt point for the repair can reduce the risk of opening up something else.
So close, keep at it!!
:popcorn:
gary.a.ayres:
Thank you, crueby :)
I did think about the grinding idea as I had heard it before, and in fact wondered if I would be given that very advice!
I think I'll give it a whirl tomorrow evening with my cheap and cheerful Dremel copy.
Regarding melting temperatures, I have already figured that in, as I used three different silver solders for the reason you suggest. Most of the soldering around the end caps was done with high or medium temp. I used low for the attempted repair and will do so again.
The encouragement is much appreciated - even knowing that you had a similar problem and fixed it is reassuring!
Cheers,
gary
crueby:
Oh yes, I spent weeks getting my first boilers to be leak free! Later ones, just many days instead... :facepalm2:
Chris
gary.a.ayres:
It can be done!!
:)
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