Stainless steel 'holding tanks'
KD6JDJ
boats and motor homes.
I was told that there is a reason for stainless coroding, perhaps due to the
urine.
Does anyone have any information about this?
Jerry
Jeff Pack
molded tanks...
Generally only in very high end bus conversions, or high end yachts.
KD6JDJ <kd6...@aol.com> wrote in message
news:19991221095828...@ng-fc1.aol.com...
brad
inside with argon or other inert gas) during welding. This will leave
contamination on the inside of the tank,causing corrosion and other bad
stuff. Good Luck-brad
KD6JDJ wrote in message <19991221194114...@ng-cs1.aol.com>...
>>From: "Jeff Pack"
>
>>they are used, just very expensive, in comparison to the
>>molded tanks...
>>
>>Generally only in very high end bus conversions, or high end yachts.
>
> I was told yesterday, about how my friend's SS holding tank sprung
multiple
>leaks in his trawler. He said that 'everyone knew about SS being unusable
for
>holding tanks.
> Now you say that they are used.
> I know Mac wouldnt have invented the story about the leaking seams in his
ss
>holding tank. I would like to know more about what happened.
> He thought that It was leaking at areas alont the welds. And he implied
that
>SS is not suitable for holding tanks.
> Now I'm beginning to wonder if the guy who welded the tank used the wrong
>filler rod.
>
> Jerry
Jeff Pack
poly tanks, which WILL crack and split over time..
I have one cracked poly tank, that I will replace with stainless.
Now like anythign else, design, and stress relief matters..
A good stainless tank isnt just a box... :)
KD6JDJ <kd6...@aol.com> wrote in message
news:19991221194114...@ng-cs1.aol.com...
KD6JDJ
Glenn Ashmore
KD6JDJ wrote:
> I'd like to know why stainless steel is not used to make 'holding tanks' for
> boats and motor homes.
> I was told that there is a reason for stainless coroding, perhaps due to the
> urine.
> Does anyone have any information about this?
Generally stainless is not used on holding tanks because the urine increases
acidity and the biological activity reduces the oxigen level. These two in
combination increase the likelyhood of crevase corrosion. This corrosion usually
starts at the welded seams. As I understand it, the heat of welding makes the
carbon migrate and concentrate at the border of the weld. A similar situation
exist for deisel fuel tanks. The USCG, ABYC and Loyds frown on stainless for
desiel tanks.
Stainless can work but the tank has to be assembled with great care. The tank has
to be filled with argon or other inert gas and the weld has to be done with
minimum heat. Also, using 316L produces a more durable weld as there is less
carbon to migrate. .
All things considered poly tanks make more sense. They cost considerably less and
have less risk of failure. If you do use poly, be sure to get high quality
rotomolded tanks. The problem is not leakage but smell. Also, the necks of
openings are the weak point. Be sure the tank is rigidly mounted and the hoses do
not place any stress on the fittings.
--
Glenn Ashmore
I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of)
at: http://www.mindspring.com/~gashmore
Doug Goncz
no carbon migration. Not sure. Sounds right, though. Soldering wouldn't do.
Frozen urine can crack a tank, then leak out. The Dog Pee Detector, a hand held
UV lamp, will find it.
>'holding tanks' for
>> boats
I've heard stainless hardware for boats must be made with great care. The
material can be corrosion resistant but the welding, as mentioned, changes all
that. Another reason to try brazing. You use a LOT of flux to dissolve those
nickel and chromium oxides. Good color matches are available. With the flux
off, a good color match, and a little hand work, it's gorgeous. With
insufficient flux it's a blackened mess.
Doug Goncz
Experimental Machinist, Replikon Research ( USA 22044-0094 )
Home Page: http://users.aol.com/DGoncz
Profile: http://www.deja.com/profile.xp?author=dgo...@aol.com*
KD6JDJ
>The problem is not leakage but smell. Also, the necks of
>openings are the weak point. Be sure the tank is rigidly mounted and the
>hoses do
>not place any stress on the fittings.
>
Glen
Your postings are always right on, and I've learned to value them.
This answer to my question is especially appreciated.
Thanks
Jerry
kenneth knaell
is not the answer to everything reminds me of a story my father told me.
This was true in the 1920's but facts might be different now.
Back around the '20s many industrial glass shapes were hand blown. Many
things you wouldn't think of were made that way. Huge glass globes for
street lights were blown, the big glass cylinders on +ACI-gas pumps+ACI- that
gasoline was pumped into and then drained into the automobile were hand
blown and I think even window glass was blown and then sagged flat. This
was not artwork, it was heavy duty hard work involving team effort. The
point is that when stainless steel first became available, the management
at the factory where my father worked decided that to keep up with
technology they would get stainless steel blowpipes for the glass blowers.
Maybe they were lighter or something. After some use which involved many
temperture cycles in and out of the +ACI-glory hole+ACI- the ends started falling
off of the pipes. (The stainless steel pipes friends +ADw-g+AD4-). They finally
went back to the material that was used to make the original pipes which
was -believe it or not- wrought iron.
I can't believe that a suitable type of SS couldn't be found today but back
then things were different.
Happy Holidays
ken knaell
Doug Goncz wrote in message
+ADw-19991222104939.10058.00000758+AEA-ng-fu1.aol.com+AD4-...
+AD4-I think brazing would make a good tank joint. Smooth fillet, stress
relieved,
+AD4-no carbon migration. Not sure. Sounds right, though. Soldering wouldn't do.
+AD4-
+AD4-Frozen urine can crack a tank, then leak out. The Dog Pee Detector, a hand
held
+AD4-UV lamp, will find it.
+AD4-
+AD4APg-'holding tanks' for
+AD4APgA+- boats
+AD4-
+AD4-I've heard stainless hardware for boats must be made with great care. The
+AD4-material can be corrosion resistant but the welding, as mentioned, changes
all
+AD4-that. Another reason to try brazing. You use a LOT of flux to dissolve
those
+AD4-nickel and chromium oxides. Good color matches are available. With the flux
+AD4-off, a good color match, and a little hand work, it's gorgeous. With
+AD4-insufficient flux it's a blackened mess.
+AD4-
+AD4-
+AD4- Doug Goncz
+AD4- Experimental Machinist, Replikon Research ( USA 22044-0094 )
+AD4- Home Page: http://users.aol.com/DGoncz
+AD4- Profile: http://www.deja.com/profile.xp?author+AD0-dgoncz+AEA-aol.com+ACo-
Leigh/Marmachine
dgo...@aol.com ( Doug Goncz ) wrote:
> I think brazing would make a good tank joint. Smooth fillet, stress
relieved,
wouldn't do.
>
hand held
>
> >'holding tanks' for
> >> boats
>
The
changes all
dissolve those
the flux
>
> Experimental Machinist, Replikon Research ( USA 22044-0094 )
> Profile: http://www.deja.com/profile.xp?author=dgo...@aol.com*
>
and you are the first person that has ever asked about brazing
stainless steel. As a structural joining technique I can think of no
reason for ever doing it. TIG welding is too fast, too clean and
stronger. Carbide parcipitation is always a hazard and brazing would
certainly encourage that. I have always thought that SS tanks were
prone to work hardening and fracture though I am sure the sulphur from
Diesel is also a major hazard.
--
Leigh Knudson ---- Machine shop owner,
woodworker, antique truck
collector-restorer and part-time machinery
dealer.
Sent via Deja.com http://www.deja.com/
Before you buy.
Doug Goncz
>With
>the flux
>> off, a good color match, and a little hand work, it's gorgeous.
>I have been in the marine hardware business for almost thirty years
>and you are the first person that has ever asked about brazing
>stainless steel.
I think it was Breakstone that marketed a corrosion resistant stainless steel
bicycle. The frame was brazed. Handy and Harman sent me a sample. I used
ordinary brazing flux, plenty of it, on an assembly of 1/2 inch tubes and 1/8
inch rods or wires, call them what you like. It was a rack to hold three boat
models in a tank to demonstrate coasting ability related to hull shapes. The
Reynolds numbers were all wrong and we had to rig the drive magnets. The
visitors to the museum never noticed, I'm sure.
The boss tried brazing it and it wouldn't stick. He had jewelry brazing
experience and used neat beads of flux. I buried the joints in flux. We used
the same torch settings IIRC. The flux came off in his bathtub overnight and
somebody filed it all to fit. The extra flux did not make for an exceptionally
difficult filing job. The torch pulled the filler wherever we wanted it to go.
Actually, I think he brazed the joints I fluxed. Anyway, that pulling is
delightful, that's how they fillet braze the classic Schwinn frame. Gorgeous,
solid metal fillets on that frame. They should spray them clear so you can see
the metal.
Cannondale weld, file, and sand lovely fillets on their aluminum frames. Klien
filled his with carbon fiber. Respiratory hazard.
>TIG welding is too fast, too clean and
>stronger. Carbide parcipitation is always a hazard
Fast heating can prevent carbide precipitation but fast cooling actually causes
it, I think. When the filler metal doesn't melt even a rapid quench with air
won't PH the metal. I worked with 17-7 PH shafts for 100 HP fans. Read a little
about it. Long ago. Certainly the carbon will dissolve into the molten metal
fully, forming a homogenous nugget. The problem with all welds is that when
they cool, the metal separates into eutectic if there is one, and into grains
and intergrain material in every case. Kind of like distilling the metal.
Instead of boiling it to separate the components, they separate as the metal
freezes. Zone refining is based on that behavior. A hot zone is dragged through
a boule or ingot, dragging with it something that belongs at the end where it
can be lopped off and recycled.
Nickel Silver melts fairly low. Don't know if it matches the color. Hell, the
little adhesive tape tag I put on the braze wire is probably unreadable by now.
But H&H will certainly send literature on brazing to anyone who owns. There's a
lot of things that can be redesigned for brazing.
Welding is a casting in place process. I'm not suggesting it be restricted to
cast work to be joined. I hear welding cast iron is really difficult. But
welding wrought work certainly forms non-wrought metal at the weld, I am sure
we can agree on that. Only seam welded EMT and a few other forms allow rework
of the weld to give it the characteristics of the wrought form.
Wash welding to "finish" a weld is particularly subject to formation of an
extremely rapidly quenched layer on the surface, which can spall. Fillet
brazing, on the other hand, makes filing unnecessary in some cases. Sometimes a
weld bead can be peened to compress that hard metal so it won't rupture. Shot
peening applies such compression to the surface of some parts, adding value in
a way similar to the way that anodizing adds value to aluminum parts. Anodized
parts can be harder at the surface, and certainly corrosion resistant, and
pretty, which are the main values added, but there is a stiffening effect from
thick shells of aluminum oxide grown on an aluminum part. I read about it in
Bike Tech in the early 80s.
We noticed corrosion on our assemblies of chrome plated steel baskets, aluminum
brackets, stainless posts, and brass screws on another tank. That one was
immersed more than the boat rails. We reworked the brackets and screws. I guess
stainless screws. I forget what the reworked brackets were made of. They sure
looked nasty after a few days in tap water. Can't demand the museum maintain
the exhibit with distilled water, although that was considered.
I do not know how stainless boat hardware is made, or how it behaves or
performs on long voyages over salt water. I do not claim to make a
recommendation for brazed over welded for that application. H&H might make such
a claim. If valid, furnace brazing of such hardware could crank them out at
much lower cost than welding. Preplaced filler and flux, jigs, and controlled
atmospheres are all options, with the furnace not necessarily owned by the
hardware designer. Surface mount electronics are furnace (oven) soldered with
various fluxes, fillers, and atmospheres. Just like baking Wonder Bread. They
really crank them out.
In space, vacuum welding of moving parts is a problem, and H&H are probably
looking at space based brazing with concentrated solar energy. Vacuum copper
brazing of steel proceeds nicely with no flux. There's a lot of stuff we use on
Earth that could be made of copper and steel, brazed in space.
And deorbiting manufacturing chips is nothing but Fourth of July!
As with medical procedures, intervention is risky and sometimes necessary. I
haven't taken an oath to do no harm to pieces of metal. Only to flesh. Not that
I don't enjoy a good rack of lamb...
mull...@advinc.com
dgo...@aol.com ( Doug Goncz ) wrote:
> delightful, that's how they fillet braze the classic Schwinn frame.
If you ever saw the jigs they used to braze bike frames, you
would not be suprised one bit.
They are *covered* with flux residue. Gobs of it. They really
slather it on when doing a frame.
When I braze stuff at work, I wait til it's cooled off a bit, and
toss it right into the boiling water (beaker goes on the hot plate
when I start the job) and most of the flux just cracks right off.
Just be careful if you are brazing brass parts, as the rapid quenching
will create porosities in the brass and cause leaks if you are trying
for a leak tight joint.
But if it is stainless to stainless, or stainless to copper,
the old torch brazer that I learned from maintained that you
could toss it in the water as soon as the solder stopped
flowing. Red hot. Goes off like a bomb it does, he said.
But it gets the flux right off!
Jim
Andrew Roberts
> Actually, I think he brazed the joints I fluxed. Anyway, that pulling is
> delightful, that's how they fillet braze the classic Schwinn frame. Gorgeous,
> solid metal fillets on that frame. They should spray them clear so you can see
> the metal.
In the begining Schwinn only let woman do brazing due to their consistency in
quality.
--------------------¦
Andrew Roberts- ¦
Napier, ¦
New Zealand ¦
¦
vill...@xtra.co.nz ¦
Doug Goncz
been quenched, and that caused the crack. Cast steel.
But as mentioned, stainless and copper quench fine and don't crack. And the
flux shatters.
Yours,
Doug Goncz
Experimental Machinist, Replikon Research ( USA 22044-0094 )
Home Page: http://users.aol.com/DGoncz
"I think you gave me too much change. May I keep it?"
Henry
mull...@advinc.com wrote:
> In article <19991223141245...@ng-cj1.aol.com>,
> dgo...@aol.com ( Doug Goncz ) wrote:
>
> > delightful, that's how they fillet braze the classic Schwinn frame.
>
> If you ever saw the jigs they used to braze bike frames, you
> would not be suprised one bit.
>
> They are *covered* with flux residue. Gobs of it. They really
> slather it on when doing a frame.
>
> When I braze stuff at work, I wait til it's cooled off a bit, and
> toss it right into the boiling water (beaker goes on the hot plate
> when I start the job) and most of the flux just cracks right off.
>
> Just be careful if you are brazing brass parts, as the rapid quenching
> will create porosities in the brass and cause leaks if you are trying
> for a leak tight joint.
>
> But if it is stainless to stainless, or stainless to copper,
> the old torch brazer that I learned from maintained that you
> could toss it in the water as soon as the solder stopped
> flowing. Red hot. Goes off like a bomb it does, he said.
> But it gets the flux right off!
>
> Jim
>
> Sent via Deja.com http://www.deja.com/
> Before you buy.
I have succssfully silver soldered stainless steel and there are many
brazing materials recomended for it but if you use the wrong flux, that is
any flux with any sulphur in it then the sulphur in the flux forms a
eutetic with the chromioum oxides on the stainless and migrates along the
grain boundries. The result is extreme britleness and cracking around the
joints. I researched this after replacing a stainless steel beer keg that
had been made into a fuel tank on a sailboat , the brazed in fittings
could be ripped out with your bare hands , leaving jaged crystaline edges
in the area of the holes for about half an inch around the brazed joints.
Henry