[modeleng] Re: Solder Qestion
- From: Bede McCormack <bede@xxxxxxx>
- To: modeleng@xxxxxxxxxxxxx
- Date: Wed, 26 Jul 2006 14:29:32 -0400
Well I've finally managed to seal up the old Conway boiler thanks to
advice from the list group and want to report back.
The short version is that, as we know, repairs like this require a
thorough cleaning and opening up of the offending gap, then ample high
temperature fluxing, then closing up the gap as much as possible (shim
or tap the gap closed), then more flux and then very high heat to flow
the comsol (296C, 564F) to a smooth finish over the leak. I used a
scratch rod to help flow the comsol and add more flux while heating.
Materials used: Comsol high temperature soft solder, and "Bridgit"
burn-resistant soldering flux, both of which I got through Reeves. I
guess the comsol is from Johnson Matthey in the UK
<http://www.jm-metaljoining.com/index.htm>, but the flux is actually
sold by a US company, J.W. Harris in Mason, Ohio, though its actually
made in Mexico... <http://www.jwharris.com/home/> I tried other
fluxes (Oatey), but they blackened before the solder melted and made a
mess. The Bridgit stuff stayed clear throughout the heating and seemed
to have worked fine, it contains Zinc Chloride, so presumably etched
into the metal a bit.
Here're a few details- In the end there were three places where it
leaked- the known leak where boiler barrel meets the throat tube along
the lower left quadrant, an expected and later realized leak around the
firehole ring, and a completely unexpected leak around the lower half
of the smokebox end of the superheater tube...
The superheater tube was a tiny pinhole and sealed right up with flux
and comsol after a thorough cleaning and picking at the approximate
position of the hole (couldn't really see it even with a magnifying
glass).
The same with the firehole ring- clean, clean clean, and pick away at
the hole itself to give the comsol a clean "purchase". The leak was
along backhead side of the upper half of the ring, so after I'd cleaned
up and fluxed the gap, I flipped the boiler onto its back and took a
bit of 3/4" round bar and gently banged the ring back up against the
opening in the backhead to seal up the gap as much as possible, then
stood the boiler on its front/smokebox end and soldered immediately so
the comsol flowed into the gap.
The barrel/throatplate hole was another story. I figured I wouldn't be
able to pick away any solid silver solder, so I picked away at the
debris/caulk with a bit of sharpened 1/8" steel rod. As I cleaned and
picked away at the hole, it gradually opened up into a real gaper- a
long, thin crescent-shaped thing almost 2 inches long, 2 cm high at its
midpoint, tapering to paper- thin at the edges. It seems the silver
solder along this seam never "took" properly, and the gap was a result
of the the silver solder coming away, and the barrel end being slightly
deformed inward, partly, perhaps as a result of my cleaning efforts.
I then made a copper shim/bung. This had to lay "flat" along the curve
of the barrel and have the correct varying height along its length
(i.e., 2cm in the middle, tapering to paper thickness at the ends). In
addition, it had to be "shim-like" so that the leading edge slipped
easily into the gap and then angled up to close the gap. 'This took a
few tries, but in the end I managed to cut and file the shim so that it
was a very tight fit and just about closed up the hole completely. I
tapped it almost all the way home, but held back the final taps 'til I
was actually ready to solder. Then I removed the shim and cleaned the
hole and surrounding area very thoroughly, running we/dry sandpaper
inside it, steel wool all along the barrel and throatplate, etc., 'til
it was all nice and shiny. Then I heated it a bit and plunged it into
the acid bath for a good soak. Then I cleaned it all over again 'til
it was nice and shiny.
Finally I was ready to solder. I upended the boiler onto its backhead
with a slight list to starboard (just two or three degrees) so the
solder would run up against the barrel (the leak was on the left side).
Then I fluxed the gap inside and out, including the area all along the
barrel and throatplate adjacent to the hole, then fluxed the shim
itself, and then banged it into the gap 'til it was just proud of flush
with the forward edge of the throatplate. then I hit it with my
Sievert torch plus two hand-held plumbers torches (BernzOmatic). I
rigged cradles out of bricks to hold the two handheld torches. This was
a lot of heat, but it brought the copper to temperature quickly until
the comsol flowed into the area, covering the length of the shim and
about 3/4" beyond with a thick, smooth layer an eighth of an inch or so
thick. Let cool and quench with water (no acid).
I plugged up all the bushes and tested the thing to 180 pounds which is
double working pressure. It held for a good half hour without any
signs of leaking, so I was happy with it. I later put all the fittings
back on and fired it using two propane torches held in the firebox and
it seems to hold fine.
One note- I fixed the superheater tube leak first, then the
barrel/throatplate leak, and lastly the firehole leak. Not sure why
in hindsight, guess I felt I wanted to keep the heatings as far from
each other as possible, both in distance, and with length of heating
required, though I imagine the whole boiler was equally heated during
each repair job.
Okay, sorry to go on, just wanted to to let anyone interested know that
repairs like this are possible, and also because I now have another
question (on lubricators) and don't want to appear ungrateful for the
advice I got for this last project!
Regards,
Bede McCormack
Brooklyn, NY
On Jun 14, 2006, at 3:50 PM, Clif Walker wrote:
> HI,
>
> I would be inclined top make up a shim and solder it in with Comsol.
> Perhaps
> a brass screw in through the side just to hold the shim in place
> whilst you
> solder
> The main problem is getting a Flux which is aggressive enough to run
> in and
> clean out the slot to ensure that the solder takes.
> In the old days Reeves used to sell a flux called Fluxall, this stuff
> would
> eat any muck in the area but the Manufacturers had to stop making it
> because
> of Health and Safety.
> I think that the best stuff that you could use now is one of the so
> called
> self cleaning fast Fluxes as use by Plumbers, One is called Power Flux
> and
> comes in a Yellow tub. Plumbers use this flux as it is so active they
> do not
> have to clean the pipes up before soldering as it removes oxides from
> the
> surface of copper.
> You can get it in places like B & Q but make sure that you wash it out
> afterwards as the stuff is so active that it will continue eating at
> the
> copper after you have finished.
>
> Best of luck
>
> Clif
>
>
>
> ----- Original Message -----
> From: "Bede McCormack" <bede@xxxxxxx>
> To: <modeleng@xxxxxxxxxxxxx>
> Sent: Wednesday, June 14, 2006 6:23 AM
> Subject: [modeleng] Re: Solder Qestion
>
>
>> Okay, I've cleaned the debris out of the leak and it looks pretty
>> dismal- about a .8mm gap approx. 1/2" long. How about if I make up a
>> 1/2" long copper shim like thing to plug the gap and comsol it in?
>> Too
>> big a gap? Maybe use a series of bronze screws and then comsol? I'm
>> in
>> new territory here, any further advice much appreciated.
>> Cheers,
>> Bede
>>
>>
>>
>
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