My new boiler - a watertube-type

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DetroiTug
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Re: My new boiler - a watertube-type

Post by DetroiTug » Sun Dec 29, 2019 7:58 pm

fredrosse wrote:
Sun Dec 29, 2019 3:58 am
Ron: "....the greater the differential in temperature between the downcomer(s) and heated elements, the greater velocity of internal circulation."

Actually, once the boiler is underway generating steam flow, there is virtually no differential temperature here, the generating coils and the downcomer liquid are at virtually the same temperature, the steam/water saturation temperature. What drives the circulation is the steam voids in the generating coils, making effective density in the coils very low compared to the almost complete liquid water situation in the downcomer(s). This large difference in effective density drives the circulation flow.
Fred, Thanks for that, :) I think that's wrong but I'll not try to prove it again, I've had very poor success rate doing that. :D I still have lots to learn.

Thanks, Ron
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Re: My new boiler - a watertube-type

Post by dampfspieler » Sun Dec 29, 2019 9:40 pm

Hi Ron,

that's how I thought it would be. The cap is removable for cleaning and inspection.

Kessel_156450_Schnitt_kplt_20191230.png

I will collect a lot of ideas before I actually build the boiler. For the first the tubes will be rebent.

- Dietrich
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Re: My new boiler - a watertube-type

Post by Lopez Mike » Sun Dec 29, 2019 10:57 pm

Upon reflection, I think Fred is right about the reason for the convection. The density difference between cold and hot water isn't that great. Plenty enough to drive vertical circulation in the oceans and in even more energy driven systems like Model T Fords and solar hot water systems.

But the circulation in our boilers is fairly violent. I've seen videos (actually films) of the surface of the water inside a boiler and it's amazing. The notion that small and maybe even large bubbles rising are the driving force makes sense to me.

I used to have an air driven dredge for cleaning out the mud next to my dock. It didn't take very much air bled into the bottom of the dredge tube to create very strong suction. Like enough to pull off your scuba glove! The deeper you were working the more alarming the action. Anything that would fit through the suction tub was sucked to the surface. Clams, rocks, gold doubloons ( I wish).
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Re: My new boiler - a watertube-type

Post by DetroiTug » Sun Dec 29, 2019 11:36 pm

Dietrich,

This is how I did mine: I added a steam dome of sorts and let it protrude down in the centerdrum and it extends below where the generating coils exit. So the upper steam head is really a ring shape. This boiler with a 300 thousand BTU kerosene burner will make steam from cold in about one minute.

-Ron
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Re: My new boiler - a watertube-type

Post by DetroiTug » Sun Dec 29, 2019 11:42 pm

Dietrich,

This is how I chamfer bevel holes on inside for welding. That is a single flute chamfer countersink tool welded to an old wrench socket, then the extension is put in an electric drill.

Also, Three different types of welding were used MIG. TIG and ARC. The ARC welder worked the best with good quality (Pro-line? I think) 7018 rods electrodes. All ARC welded joints were sealed and required no repair.

Another thing to keep in mind, any joints exposed to water, should be butted together with out a space in between. This is what causes rolled in tubes to leak over time, water lays in between and corrodes the steel. This is in line with welded steel boat hull fabrication, they use no lap joints, or shouldn't anyway.

-Ron
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Re: My new boiler - a watertube-type

Post by fredrosse » Mon Dec 30, 2019 5:28 am

From Lopez Mike:...."I used to have an air driven dredge for cleaning out the mud next to my dock. It didn't take very much air bled into the bottom of the dredge tube to create very strong suction. Like enough to pull off your scuba glove! The deeper you were working the more alarming the action. Anything that would fit through the suction tub was sucked to the surface. Clams, rocks, gold doubloons ( I wish)."

Apologies for getting a bit off topic, however I spent time working for the US Army Corps of Engineers, Inland Waterways Dredging Operations. Oceangoing steamships with dredge piping (about 48 inch diameter), gate valves, expansion joints, etc. All of this dredge piping would wear out quickly, due to abrasive rocks, sand, clam shells, etc. and whatever flowing in the pipes. Where there was a flow pocket, such as the seating area for a gate valve, heavy metals would accumulate because the high density metals would resist being washed out of any crevasse. Just like the "panning for gold" principal.

In the shipyard for repairs and worn piping replacement, the workers would always crowd around a piece of piping near a dredge valve that was having its flange unbolted, they were hoping for gold doubloons too! Never saw any gold or silver, but almost always large amounts of lead bullets, thanks to the US Navy dumping ammunition into the rivers and harbors for many decades.
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Re: My new boiler - a watertube-type

Post by Lopez Mike » Mon Dec 30, 2019 11:51 am

The potential for trapped water in such places as tube ends is one of the reasons I store my VFT dry when laying it up for the Winter (when I'm away in Mexico for six months!!). Blow down dry and then apply fairly vigorous heat for a day or two. Like too hot to touch. Then a nice long suction treatment of the piping with my shop vacuum. It does freeze once in a while where the boat lives. Works way better for me than blowing things out with compressed air.

Ron, I'm dazzled by the wall thickness of that central tube. Looks like you were planning on using it for a scuba tank. I'm sure it would pass a hydro test to a thousand pounds or so. And hurrah for 7018. Almost makes a welder of me (Not!).
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Re: My new boiler - a watertube-type

Post by DetroiTug » Mon Dec 30, 2019 4:39 pm

Quote: "Ron, I'm dazzled by the wall thickness of that central tube. Looks like you were planning on using it for a scuba tank. I'm sure it would pass a hydro test to a thousand pounds or so. And hurrah for 7018. Almost makes a welder of me (Not!)."

Yeah, that's a whopper isn't it? Haha Well, in the application the driver and passenger are literally sitting on top of the boiler, it's comforting to know that the boiler is constructed so well. It has a working pressure rating of 2400 psi. We hydro'd it to 800 psi and that was plenty. I run it at 250. Lots of added safety with little added construction weight. The boiler weighs 99 pounds.

-Ron
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Re: My new boiler - a watertube-type

Post by dampfspieler » Tue Dec 31, 2019 10:50 pm

Hi Ron,

thanks for showing the interesting detail of yours.

I will built a pipe cross from 1/2" gunmetal nipples like this (my little experimental boiler) for steam exhaust.

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The data of yours are very impressive, i will run my only with 7,5 bar (105 psi). Which valves and controls have you installed?

-- Dietrich
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Re: My new boiler - a watertube-type

Post by DetroiTug » Sat Jan 04, 2020 3:02 am

Apology for so long in responding.

That is very nice work on your boiler, I must commend you for your ability and patience in soldering.

The pipe that is in your pic, if any water goes over the top it does not look like there is a way for it to return to the center drum and will assuredly exit through the piping. I don't think the threat of carry over is too much concern. As I wrote above, my friends boiler simply has a hole in the center in the upper head with a "T" welded to it and he has never mentioned carry over problem and he runs his car very often. He's never had any water damage to the engine. He's had many lower end issues, because he runs his system at 400 psi and the engine was really designed for 200 psi. He runs his steam bike at 800 psi, it sure makes that little "1/4 Horsepower" Charles Strelinger/PM research engine sing at about 1400 RPM, he has broken and repaired it many times. He built a new 3 cylinder engine using three of those engine kits. I think he got all three for 750 dollars at the Engineering modeling show NAMES show.

The valves I am using. This is for my Locomobile steam carriage, the steam plant is very simple and very basic. Only have the necessities. Feed pump and hand pump, throttle, and relief valve. The fitting out the bottom of the drum to the lower sight glass provides good accurate reading during operation. It acts a bit strange at fire up, rising very high and then subsiding and stabilizing. The sight glass is about 20" away and when I go around left corners, the water goes up and when I go around right turns the water goes down. The top fitting for the glass is connected to a line that I use as a "top blow", this is a valve for getting rid of excess water during fire up or if we forget to open the bypass and overfill with the feedpump while driving, all it takes is a pretty girl to get the valves clattering :) , we usually fire up with the boiler completely full for about 20 seconds and then start valving it off. My Ofeldt only has about a gallon of water, but it will run about 1 or 2 miles with that volume.

I also use the top blow at shows, the car is so quiet with the muffler, I hear people talking when I drive past and I hear them say something like "oh that is an early electric car" and then I give a couple blasts with the top blow out the back to let them know that it's steam. They look very puzzled.

-Ron
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