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Re: Stainless steel boiler/exchanger?

Posted: Thu Oct 12, 2017 10:23 am
by NP317
Carrdo wrote:The Australians and the New Zealanders are way ahead of us when it comes to research, testing and experience with the use of stainless steels in live steam locomotive boilers.

Just Google "Live Steam Boilers Duplex Stainless Steel" or just "Duplex Stainless Steel" and you can read the numerous articles written about this material and what has been done with it.
I am not trying to influence anyone one way or the other.
Quite true.
But note the specific "Duplex SS." This is a unique alloy with stainless properties, and not your "undefined" stainless alloy.
And research and testing backs up the usage in boilers, as a superior material.
Probable expensive, too.
~RN

Re: Stainless steel boiler/exchanger?

Posted: Thu Oct 12, 2017 11:12 am
by Builder01
NP317 wrote:
Carrdo wrote: Probably expensive, too.
~RN
More than copper?

David

Re: Stainless steel boiler/exchanger?

Posted: Thu Oct 12, 2017 4:34 pm
by BClemens
This is not a new topic but most interesting all the while....
Here's another slant in a similar direction with some good points:
https://www.morebeer.com/articles/brazi ... _stainless

It's a good read anyhow.

Our interest is in Marty Knox's (our well known universal boiler expert) input toward Silver Soldering Stainless Steel - in the interest in eliminating the 'weld effected zone' with fusion welding stainless steel - which also eliminates the problem of - weld failure of stainless boilers.

Thanks,
BC

Re: Stainless steel boiler/exchanger?

Posted: Fri Oct 13, 2017 1:03 am
by Harold_V
BClemens wrote: in the interest in eliminating the 'weld effected zone' with fusion welding stainless steel - which also eliminates the problem of - weld failure of stainless boilers.
I'm not convinced silver soldering would avoid problems, as heating between the range of 800°F and 1,500°F offers the opportunity for intergranular corrosion. That condition can be minimized by selecting 304L.

H

Re: Stainless steel boiler/exchanger?

Posted: Fri Oct 13, 2017 9:05 am
by Marty_Knox
BClemens wrote:Our interest is in Marty Knox's (our well known universal boiler expert) input toward Silver Soldering Stainless Steel - in the interest in eliminating the 'weld effected zone' with fusion welding stainless steel - which also eliminates the problem of - weld failure of stainless boilers.

Thanks,
BC
The way I read it Harold is right - brazing the joints does not eliminate the 'heat affected zone'. Another point you may have overlooked is that a butt brazed loint does not have the strength of a butt welded joint. To make a brazed joint stronger you increase the area that is brazed, typically by lap joints with a lap 3 x the thickness. This would require you to flange the plates. I cannot imagine what it would take to flange 304 or 316 stainless steel.
And yes, I know what it takes to work stainless steel. Two of my test pieces to qualify as a Boilermaker First Class were a square to round 16" square to 12" diameter, and a 10" diameter 5 gore elbow - done in 316L!

Re: Stainless steel boiler/exchanger?

Posted: Fri Oct 13, 2017 9:15 am
by Marty_Knox
As for the Duplex stainless steel I was informed about it right from the initial proposals, thanks to Fred Springer and Mike Massee. It may well be the wave of the future for our small boilers. I got as far as requesting a quote from Sandvik, but they wanted the drawings as a DWG. file, with all dimensions in metric. That stopped me - I had tried teaching myself CAD. I spent almost 3 hours on a drawing, only to hit the wrong button and have it disappear forever!
Also, the welding requirements are pretty stiff.
If I were 30 years younger and planned to build boilers for another 30 or 40 years I would put it the time and effort to master the Duplex Steel fabrication.
But I made the business decision NOT to pursue it, and stick with what I know.

Re: Stainless steel boiler/exchanger?

Posted: Fri Oct 13, 2017 9:35 am
by BClemens
CAD software is similar to a video game - you're trying to beat the game by making a drawing that makes sense. Then there is 'solids' CAD....
I use it here at work along with CAM software. If you send me a sketch, I will most happily make a drawing for you in any file format you need.

The thought with silver soldering the ss was to use lap joints - like as you said - machined to half material thickness for a three or four full thickness lap. I still have a piece of Ø6" 304L that I'm itching to do something with. Welding is out and with this kindly advice, soldering is out too. It is still standing on the floor in the shop ever since Bruce Mobray told me about the corrosion problem and that I would never run on his track with a Stainless Steel boiler. I took his advice but it is still such a beautiful piece of ss pipe!
BC

How about monel? It tig welds like ss and is corrosion resistant similar to copper. But I don't even want to know the price of it!

Re: Stainless steel boiler/exchanger?

Posted: Sat Oct 14, 2017 12:43 am
by Harold_V
BClemens wrote:
How about monel? It tig welds like ss and is corrosion resistant similar to copper. But I don't even want to know the price of it!
If you have deep pockets, yeah, it's the ideal choice.

H

Re: Stainless steel boiler/exchanger?

Posted: Sun Oct 15, 2017 1:26 pm
by Asteamhead
Hello BClemens,
You m u s t n o t even think about soldering boilers made of stainless steel! :evil: It' dangerous, believe me!
Changing temperatures in combination with some mechanical stress will destroy every silver-soldered connections after some time of use.
Stainless steel 304 - or even better - 316 L (1.4571) my be used for tubes or boilers. TIG-welded, of course.
A lot of boilers of different sizes made of SS 1.4571 are in service here in Europe. Some of them are 40 years old now.
'Duplex' steel was introduced and marketed by cy. Sandvik (S) as a less costly replacement for more standard SS steel like 1.4571 or 316 L. No advantage regarding corosion or durablety but o.k., too.

By the way, my new N&W class A 1239 has a medium size boiler of 11 " diameter made of 1.4571. It was welded by a professional welder and certified as well.

Boilers for use with big size 7.5 " locomotives may be made of convential boiler steel for reasons of costs and easier production process.

Asteamhead

Re: Stainless steel boiler/exchanger?

Posted: Sun Oct 15, 2017 9:51 pm
by Comstock-Friend
Tom Miller's, Doug Alkire's and Dave Moore's stainless boilers were all T321H (Titanium stabilized). Doug Alkire explains it all in "So you want to build a live steam locomotive'.

Doug did have some misleading comments about the heat transfer aspects of a stainless boiler. He put copper tubes in his for the better conductivety. The gas to tube heat transfer coefficient is controlling and much less than either the copper or stainless conductivity and especially less than the boiling heat transfer on the tube to water side. You would not notice any difference in steaming qualities between stainless or copper.

Water care is certainly in order on the stainless boilers.

John

Re: Stainless steel boiler/exchanger?

Posted: Sun Oct 15, 2017 11:18 pm
by BigDumbDinosaur
BClemens wrote:Our interest is in Marty Knox's (our well known universal boiler expert) input toward Silver Soldering Stainless Steel - in the interest in eliminating the 'weld effected zone' with fusion welding stainless steel - which also eliminates the problem of - weld failure of stainless boilers.
No, it will not eliminate the problem. Silver soldering requires that the base metals be heated into what is referred to as the sensitizing zone, which is when the carbide precipitation will start.
Harold_V wrote:I'm not convinced silver soldering would avoid problems, as heating between the range of 800°F and 1,500°F offers the opportunity for intergranular corrosion. That condition can be minimized by selecting 304L.
Note Harold's comment: "minimized." Carbide precipitation cannot be avoided, only minimized.

Incidentally, 800°F is the start of the sensitizing zone for austenitic steels. Once you enter it all bets are off on the final metallurgy.

Re: Stainless steel boiler/exchanger?

Posted: Mon Oct 16, 2017 9:28 am
by michaellynn2
Folks , I have no experience with stainless boilers except one. A boiler inspector in the state of VA. told me he would never pass a boiler that he would inspect made of stainless.