Ballaarat copper boiler

Latest instalment refers to Tobin Bronze. I've tried google, which refers me to a racehorse. Anyone know what it is? SifBronze?

Here ya go!

& more data here too.

(search for -> Tobin bronze brazing

is the way to go).

Phil

Edited By Weary on 02/11/2022 19:19:28

Edited By Weary on 02/11/2022 19:26:29

A bit below the racehorse, I found this. So it's a corrosion-resistant copper-based alloy - I suspect the next issue would be finding a supplier.

Rob

Edit - must type faster!

Links to https://dl.asminternational.org/alloy-digest/article-abstract/5/5/Cu-38/438/TOBIN-BRONZE-452Corrosion-Resistant-Copper-Base?redirectedFrom=fulltext

Edited By Grindstone Cowboy on 02/11/2022 19:11:44

So it's copper and zinc with a touch of tin (1%), which makes it brass. Will it de-zincify? Academic anyway for me, doesn't come up on ebay UK search Aus and USA only suppliers

The AMBSC code allows the use of Tobin bronze brazing in boilers. You may use an unflagged joint between the throatplate and barrel, so long as the throatplate is set inside the barrel opening, not butting onto its outside. The reason is obvious. This saves a double flanged throatplate and is what I always do. Bronze brazing isn’t much fun as the copper must be glowing orange before the rod will flow and I find it hard to see what’s going on. The Code states that only those experienced in bronze brazing should use it, but how do you get experienced?
I have wondered about dezincification. Presumably that 1% tin makes all the difference.

The AMBSC code allows for both bronze brazing and silver brazing; with a wide range of allowable filler metals (other manufacturer’s equivalents are specifically allowed). The only limitation is phosphor bearing alloys or silver bearing alloys with Ag below 15%, which is not allowed. TIG welding of copper boilers is allowed in this code.

Dezincification is an interesting topic. I've found that diffusion or leaching of alloys that are in solution is not very common (and results in a pitting), but if these alloys are on the grain boundaries you may have an issue (cracking). This typically occurs if the transition past the liquidus of the low melting alloy is too slow.

I personally think the silver brazing or TIG welding route would be easier for a beginner.

The AMBSC code does not permit TIG welded copper joints except by suitably certified welders.
A beginner should do quite a few practice joints when beginning to silver solder. This is especially so for bronze brazing where you risk overheating the copper. You really need oxy-propane/acetylene for bronze brazing, although propane will do the job for an isolated assembly such as foundation ring section to inner firebox wrapper as a first operation. I would always prefer high temperature silver solder if I had it in stock.

Yep and unfortunately, unlike the AMBSC stainless code, there is no allowance for supervising an amateur welding his boiler. An interesting inconsistency in the AMBSC codes. It is highly unlikely you will find anybody with the correct certification and recent expieriance as required by the code. My view of certified welders…

This was welded by a qualified, experienced, certified welder and passed inspection. This was for a very large Australian company.

This was welded by an amateur with no official experience, certifications or welder qualifications to try show the company what it 'should' look like.

Destructive testing...

Nuff said…

Is that actually weld on the first photo, colour of filler rod looks more like it was TIG brazed?

Would be interesting to see if the other side was a better "weld" as access may have been a bit tight from the side where the photo was taken depending on scale of job.

Edited By JasonB on 04/11/2022 07:22:39

Yep, AlBr filler rod, MIG. The pre-heat and interpass temperature was completely wrong, not to mention the welder was holding the gun incorrectly. The copper welding they did was worse.

Its a big job, those bent plates are 10mm thick. Other side looks like this...

The paint is for specific testing.

I think the point I'm trying to make is the requirement for a certified welder for ME boilers scares me. The one professionally made boiler we had at the club (71/4 Romulus, made in the UK) failed dismally and there were a few welding techniques that were simply unsafe. From what I've seen in industry the skills are not nearly as good as the amateur welders that have built their own boilers (at our club). We are very fortunate to have a boiler inspector that understands engineering first principles, and has himself, built more than half a dozen of his own boilers.

I have made my thoughts on this clear before ! BUT there are good and bad professional welders as there are good and bad amateur welders. Luker says it all when he mentions his club inspector and him being a practical man !

where or how do you draw the line ? Noel.

.

Frankly … it’s the wrong decision criterion

an Amateur ‘does it for love’ and a Professional ‘does it for money’

in itself, that is not sufficient to predict who will do the better quality of work.

MichaelG.

I agree; as with anything there is a standard distribution, my sample set is very much skewed to one side (if there was any doubt, amateurs win!).

The line should be drawn by the boiler inspectors. It’s their job to determine if the boiler is fit for purpose by testing etc. I think the same onerous criteria for welding qualifications should apply to the boiler inspectors. In other words, they should be highly qualified and/or certified, with practical experience in building boilers. Let’s just peg it to a few tertiary engineering degrees and they must have, at least, completed 5 boilers to qualify! Seems a little ridiculous?

It appears that SifBronze is the UK equivalent of Tobin bronze. Intrigued as to why it's acceptable in a boiler as it has high zinc content I emailed Weldability, who are the UK manufactures. This is their response

Dezincification of Brass has always been an issue over time and you are correct in the use of Tin to eradicate this, or at least slow it down which is why 0.3% Sn is added.

Its academic to me as I don't have oxy, so I'd use high melting point silver solder

In ME 4702 21 oct-2 nov pgs 569-571 there are drawings for the Ballaarat copper boiler. In my copy, all the object lines in the views are coloured light grey, along with the crosshatch. This essentially makes the object in the views invisible and the drawings are completely useless. The dimension lines are black as expected.

ME editors - are you aware of this error in some or all copies? will you be publishing usable drawings in future?

If you're getting bad drawings I would start a dedicated thread