Subject: Where to find sources on sanitary welding?

From: [email-masked] (Teddy Winstead)
Date: Mon, 10 Oct 1994 17:36:17 GMT

I've become interested in sanitary welding for building my (ever expanding)
home brewery.  Does anyone know of any good sources for information on
this topic?  I don't even know where to start looking...
-- 
Nathaniel Scott "Teddy" Winstead         |  Try Linux -- The Homebrew of
[email-masked] (Preferred)       |  Operating Systems!
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From: [email-masked] (Jim Driscoll)
Date: 11 Oct 1994 17:53:54 GMT

I have been unable to find any book on sanitary welding.  If you do
find something of that sort I would appreciate hearing about it.

Your post didn't give much of a clue as to your knowledge of metal
fabrication, so here goes an explanation that may or may not be
optimally intelligible or useful:

The material I use is type 304, but some prefer 304L for increased
weldability.  I am usually using 12ga, but for a homebrew setup 18ga
is about as thin as I would go to still be easily weldable.  For this
gauge, the mill finish, 2B, should be sufficient for homebrewing, but
you can get a #3 or better yet a #4 finish for the inside if you are
feeling generous.  I would recommend getting the material with
removable protective coating for the inside that will protect the finish
while you build the equipment.  You can cut it away from joints with a
home-made copper blade made by grinding a squashed piece of copper
tube.

Never let anything made of mild steel touch your stainless, and
don't use anything that has touched mild steel on it either (e.g. a
grinding wheel).

The welding method of choice is TIG or GTAW.  Be scrupulous about your
tungsten!  always grind it to a point on a grinding wheel reserved for
only tungsten, and if it it touches the weld puddle immediately cut
off and regrind the tip.

I butt weld joints.  For tanks tack weld the compennents into position
with as close a fitup as possible--it is worth the trouble.  I use
hydraulic spreaders and cargo load straps to bring things into
position/into round.  I then weld the inside with filler rod,
penetrating say 2/3 of the joint, then weld the outside with filler.
I am moving toward backing the joint on the outside with flux or a
consumable weld backing material and then making one pass on the
interior.  Alternatively, you could back it with inert gas, but this
won't support the weld puddle.

After welding I use what I think are called polifan wheels from Pferd
abrasives mounted on an angle grinder to grind/finish the weld on the
interior.  To get a better finish I use flap wheels or non-woven nylon
abrasive wheels mounted on a straight grinder afterwards.  After this
has been done, the weld should not be visible, there sould be no pits
or high spots.  About the only thing you should be able to detect is
a difference in finish in the area of the weld.

For a really fine finish you can send the finished assembly to an
elecropolisher, but unless you are Coors, this is usally reserved only
for yeast propagation plants.

Now here comes the tricky part.  Most people will tell you that you
must passivate the heat affected zone, by which they mean that the
free iron brought to the surface by the welding process is removed and
the protective chromium oxide layer is restored.  My experience is
that if the heat affected zone is finished well with suitable
asbrasive materials the joint will not corrode.  For your purposes you
can probably use it as finished, and if you note any corrosion, it can
be removed with the green hand pads sold at your local grocery store
for dishwashing.  If you insist on passivating it, I can tell you how
it can be done, but it requires using dangerous acids.

You should be aware that "fresh" stainless steel has a taste.  When
commercial brewers bring a new piece of equipment on-line, they first
fill it with finished beer, let it sit a bit, and then discard the
beer.

	Good luck,

	Jim Driscoll
	Driscoll Brewing

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From: [email-masked] (KLM)
Date: 12 Oct 1994 15:41:53 GMT

In article <[email-masked]>,
Randy Lee <[email-masked]> wrote:
>In Article <[email-masked]>,
>>
>>weldability.  
>Snip a lot of realy good info on sanitary welding....
>
>Jim, What about lead leaching out of the 304L (the L stands for about .5%
>lead added to improve the machineability of the steel) in to the somewhat

Actually, the L stands for 'xtra low carbon'. Something (an oxide of titanium
et al) is added that binds with carbon to form carbides. I may have the
chemistry wrong, but the intent is not to increase the machinability, but
increase the corrosion resistance in the as-welded condition. 304 and 316
(as opposed to 304L and 316L) have a tendency to corrode at the weld. Note
that you can use 316L wire on regular 316 or 304 material for some protection.

There are high machinibility stainless alloys with added selenium, e.g.
303Se. Using these, or valves/fittings made with these, might be a concern -
I just don't know. 

The nonstainless steels, like 12L14, do contain lead, as has been posted.

sources: Machinery's Hndbk, 24th ed, pp 373, 1007.
         my dim memory (for the exact chemistry of the carbon binding)

ps: the chart of free machining stainless alloys on p 1003 lists
some other kinds: 303MA, 303Pb, 303Cu, 303 Plus X. I've never heard of
these (unlike 303Se) elsewhere. There is no composition listed, but
the Pb sounds suspect.

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From: [email-masked] (Randy Lee)
Date: Wed, 12 Oct 94 14:28:27 GMT

Jim, What about lead leaching out of the 304L (the L stands for about .5%
lead added to improve the machineability of the steel) in to the somewhat
active contents of the brew? I know you said you use the 304 but I am a bit
stonkered that 304L could be used in food prep. in this day and age when the
max allowed lead is constantly being lowered!

~R
________________________________________________________
Randolph Lee    [email-masked]  [email-masked]
Tag space For rent!.... Inquire Above for atractive rates!

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From: [email-masked] (Jim Driscoll)
Date: 12 Oct 1994 16:21:28 GMT

Randy Lee asks:

> Jim, What about lead leaching out of the 304L (the L stands for about
> .5% lead added to improve the machineability of the steel) in to the
> somewhat active contents of the brew? I know you said you use the 304
> but I am a bit stonkered that 304L could be used in food prep. in this
> day and age when the max allowed lead is constantly being lowered!

Type 304L is a Low carbon variation of type 304 with a maximum carbon
content of .03% max as compared to .08% max for 304.  The lower carbon
content helps avoid carbide precipitation due to welding, but the
tensile and yield strength are somewhat reduced.  Type 303 is the free
machining version of type 304.  None of these are alloyed with lead,
and I am sure that the max allowable lead content is quite low.  This
could probably be looked up in The Metals Handbook, which I really
should buy a copy of.

I can't find any specific limit for lead in beer, but for bottled
water the limit is 0.05ppm.  In Britan there is a limit specifically
for beer that is 0.2ppm.  The only study I know of found .06ppm in a
lager beer.  The American Society of Brewing Chemists has no standard
method for the determination of lead in beer which leads me to believe
that it is not specifically regulated beyond the FDA's general
standards of good manufacturing practice.

	Jim Driscoll
	Driscoll Brewing

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From: [email-masked] (Nick Turner)
Date: Mon, 17 Oct 94 09:51:08 GMT

>this topic?  I don't even know where to start looking...

Well as far as I can recall the place to look would be in the welding standard 
for food grade. well thats how it works here there is a welding ticket that 
you sit and when you have that you it means that you can weld to the required 
standard  for that industry. As far as I can remember this involves a smooth 
surface that won't harbour the dirt and a few other factors. 

If you whish to learn to do this try a polytech, 
(trade training centre) if you just want to know about it try the library
in the section that keeps the standards, if you only want the stainless steel 
vessels go out and buy them second hand they will be much cheaper and can be 
modified  to suit your needs, I would start by investigating the dairy 
industry  as they tend to use a lot of this sort of thing. Localy we get beer 
iin fifty litre kegs which are made from stainless may be ideal for your needs.

 Nick