What are the concerns/safety of an unfired >100C vessel

A special section just for steam engines and boilers, as without these you may as well fit a sail.
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cyberbadger
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Re: What are the concerns/safety of an unfired >100C vessel

Post by cyberbadger » Thu Oct 26, 2017 12:29 pm

Fred,

Confused about what you are referring to.
Lopez Mike wrote:I have been using ordinary 5/8" copper pipe with flare fittings for my steam pipe from the boiler to the engine for some years now. After three to four years I see a small wisp of steam and find a small crack running around the pipe right at the base of the flare. It doesn't fail catastrophically and I have just been replacing the whole 18" pipe when this happens.
http://www.thesteamboatingforum.net/for ... f=8&t=1906
Flex pipe thread

That was also copper. I haven't used copper much anymore for sometime except for in special cases (Windemere Kettle).

I'm using SS for tubing and here the tube wouldn't actually be of any significant length, the ss flex hose is doing the real flexing.

I've heard some arguments for and against swagelok fittings for steam elsewhere, it's interesting to note that swagelok has a special steam application group for it's customers.

What capacity (I'm assuming you are using the lbs/hr in a calculation) would be acceptable? Are you suggestioning that to use this safety valve would just open up and dump if you opened the valve to start transferring water.

-CB
Last edited by cyberbadger on Thu Oct 26, 2017 5:14 pm, edited 1 time in total.
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barts
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Re: What are the concerns/safety of an unfired >100C vessel

Post by barts » Thu Oct 26, 2017 5:10 pm

The Swagelok vs 37 degree flare? That is like comparing a modern BMW to a model T Ford in terms of performance. I hope some of our experienced steamboaters on this forum can chime in here and verify what I am saying. The Swagelok fitting can take 3000 PSI with many many connect/disconnect cycles.
I've had nothing but excellent service using Swagelok fittings w/ stainless for either steam or hot water. I use one for my whistle connection on Otter, so it gets attached & detached every time I launch the boat. I also used these to provide a top connection for my reflex gauge glass.

I've not tried flared stainless, but I've had work hardening and cracking issues w/ copper flares; they're just not well suited for repeated make & break.

- Bart
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Re: What are the concerns/safety of an unfired >100C vessel

Post by cyberbadger » Thu Oct 26, 2017 5:27 pm

barts wrote:I've not tried flared stainless, but I've had work hardening and cracking issues w/ copper flares; they're just not well suited for repeated make & break.
What exactly the cracking issues encountered and the failure modes are what I am concerned about. If you flair either copper or stainless sometimes if you don't have the tool adjusted right or crank it too much you will get those cracks.
I usually cut if off and try again. With copper I think it will just fatigue eventually and crack. But is it always just a wisp of steam as Mike was describing? Or can it be more violent? Same question for the swagelok fittings.

I was talking to my buddy and he uses swagelok a lot at work, not for steam, but very high pressures and thinks they are good, but questions how it will fail under steam. I told him how many tightenings till it won't tighten, and how does that actually compare to my expected use. Swagelok doesn't seem to give an actual average, just "many times".

Is this something that there may be a study on or an ASME case study? (Or statistics on accidents?) Clearly in industry they do use both.

-CB

P.S. I'm specifically talking about the AN fittings with the 37deg flare. The 45 is similar, but I think the AN (Army-Navy) is superior to the 45.
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Re: What are the concerns/safety of an unfired >100C vessel

Post by DetroiTug » Fri Oct 27, 2017 12:41 pm

barts wrote:If you flair either copper or stainless sometimes if you don't have the tool adjusted right or crank it too much you will get those cracks.
Thin copper is bad about that. Other causes are trying to make the flare too large, one big help for fractures, use a propane torch and heat the end up red hot and let it cool slowly (anneal) before flaring.
barts wrote:Is this something that there may be a study on or an ASME case study? (Or statistics on accidents?) Clearly in industry they do use both.
My own personal experience with copper lines, I had a line fail going to my white fuel pilot lights on my car and about lost the whole car as a result. Copper is sorta ok in an application where is stays connected and there is no motion or vibration, copper can work harden and fail in short order. I knew better, but followed along with the practice of that arena of hobby steam. Not any more. Copper for fuel lines and brakes lines is strictly prohibited by the DOT due to the simple fact it can fail easily in some applications. I replaced all the fuel lines with PTFE lined stainless braided hoses that one can make up themselves. McMaster sells the hose and various ends for assembly to any length or configuration needed. More expensive than copper of course, however, it can handle vibration and rough duty. And if the inner hose were to fail, it's not going to simply drop off like copper can resulting in a wide open line. The braided sheath will keep it together.

How does copper fittings compare to Swagelok? Fred said it, BMW to a Model T.

-Ron
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Re: What are the concerns/safety of an unfired >100C vessel

Post by cyberbadger » Fri Oct 27, 2017 3:46 pm

PV.jpg
150MAWP Fireless Pressure Vessel
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There is a quarter on the right elbow for a sense of scale.

It can be folded side by side using two elbows - but then the drain and steam space isn't as ideal.

Well, I should be getting some swagelok to try...

-CB
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Re: What are the concerns/safety of an unfired >100C vessel

Post by cyberbadger » Fri Oct 27, 2017 11:08 pm

And the swagelock fitting.

So I am going to start putting this together, then a hydro.

-CB
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Re: What are the concerns/safety of an unfired >100C vessel

Post by RGSP » Sat Oct 28, 2017 11:09 am

It may have been a misprint or slip in a posting above, but annealing copper is almost exactly opposite to annealing most steels: in other word to anneal copper most effectively, you heat it to dull red, and then plunge it into water.
Heating it up and allowing it to cool slowly will remove some work hardening, but it will not be anything like as soft, or have the same extensibility before fracture, as when properly annealed.
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Re: What are the concerns/safety of an unfired >100C vessel

Post by DetroiTug » Sat Oct 28, 2017 12:27 pm

RGSP wrote:It may have been a misprint or slip in a posting above, but annealing copper is almost exactly opposite to annealing most steels: in other word to anneal copper most effectively, you heat it to dull red, and then plunge it into water.
Heating it up and allowing it to cool slowly will remove some work hardening, but it will not be anything like as soft, or have the same extensibility before fracture, as when properly annealed.
This is contradictory to annealing that I've done over the years and how I understand it. I'm going to give it a try to see what the difference is. Heating copper to dull red and allowing it to cool slowly has always worked for me, allowing the metal to be worked in to shapes that would assuredly fracture otherwise. Not sure how much softer it could be or even needs to be.

Annealing allows the molecules in the metal to flow and fully align themselves in the most malleable and soft configuration as the metal cools slowly. Dousing it in cold water abruptly halts this natural alignment process and leaves the material in a stress known as either hardening or tempering. This happens with other metals, even aluminum. When I build aluminum weldments, I heat them up and douse them, otherwise they machine like mud. Even low or no carbon steels will harden (some) and anneal, been told many times otherwise. They don't behave like high carbon tool steels, 65 Rockwell is not going to happen without carbonizing, but they still react to a certain degree to hardening and annealing with a state change in the material.

-Ron
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Re: What are the concerns/safety of an unfired >100C vessel

Post by fredrosse » Sat Oct 28, 2017 12:42 pm

"It may have been a misprint or slip in a posting above, but annealing copper is almost exactly opposite to annealing most steels: in other word to anneal copper most effectively, you heat it to dull red, and then plunge it into water.
Heating it up and allowing it to cool slowly will remove some work hardening, but it will not be anything like as soft, or have the same extensibility before fracture, as when properly annealed."

All the technical literature I have (I collect old engineering books, and have hundreds) indicates that annealing Copper is done by heating it to transition temperatire, and then you can let it cool slowly, or plunge it into water, virtually no difference ever mentioned.

I have done this annealing process many times, letting the Copper cool slowly, and often times plunging it into water when I am in a hurry to work with it. In my experience I have never noticed any difference in the annealed properties whatsoever.

Looking up "Annealing" on the internet......"In the cases of copper, steel, silver, and brass, this process is performed by heating the material (generally until glowing) for a while and then slowly letting it cool to room temperature in still air. Copper, silver[1] and brass can be cooled slowly in air, or quickly by quenching in water, unlike ferrous metals, such as steel, which must be cooled slowly to anneal. In this fashion, the metal is softened and prepared for further work—such as shaping, stamping, or forming."

This article goes on and on with grain size and grain boundary stuff, Gibbs function, etc. But I am no rocket scientist, so...

I am anxious to hear Ron's results here, a simple test may show some small difference.
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Re: What are the concerns/safety of an unfired >100C vessel

Post by cyberbadger » Sat Oct 28, 2017 2:16 pm

Fred,

Any ideas about the sizing you were talking about?

I could put either the ASME 125set Aquatrol or (not following the code exactly) the single spring ATAM relief valve could be set to 150psi.

-CB
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