Ofeldt boiler

[DetroiTug]

Putting an Ofeldt boiler together. This is for a car, but it would work in a steamboat as well. 17.8" diameter X 17" overall height.













-Ron

[fredrosse]

Any detail information available: Pressure, materials, burner, etc?

[DetroiTug]

Hi Fred,

The 6" center drum is ASTM-A106 Schedule 80 tube. The coils are wound from good quality 1/4" Schedule 40 pipe (A53 I think). According to the piping charts they both have a working pressure of around 2100 psi. It will be ran in the 400 psi range. I doubt the 1901 Loco engine would like 2100 psi

Should do a pretty good job, my buddy has a similar boiler with only 12 coils and it runs his 2.5 X 3.5 twin Mason very well.

The fuel tank will be schedule 40 6" pipe with endcaps inset. It will have an air over fuel pressure in the range of 80 psi.

Going to use kerosene as primary fuel, or gasoline/petrol as a backup. These will burn about anything. The burner is a vaporizer tube type. The burner itself will be an Ofeldt style. The burner is similar to the boiler, having a center drum of the same diameter and tubes that go out radially in a sunburst design. These burners do not emit flames under the center drum of the boiler. We have surmised that doing so would disrupt the internal circulation of the boiler. Whereas flames impinged on the generator tubes pull water in from the bottom and emit steam at the top back in to the center drum. Any water simply goes back to the bottom and then re-enters the tubes.

These are very powerful generators for their size. Similar to a flash boiler, but the center drum provides some reserve.

I'll post a pic of the chassis in the "Anoraks corner" section.

-Ron

[87gn@tahoe]

Looking good Ron.

How many pound per hour do you think that boiler evaporates?

What do you think your time and materials investments are?

~Wes

[barts]

Looks nice. Did you have those coils wound, or did you manage that yourself?

- Bart

[DetroiTug]

Hi Wes,

I have no idea on the PPH. There is roughly 23 sq ft of water tube. Someone wrote 5 sq/ft per hp on a firetube and 2sq/ft per horsepower for a water tube. Judging by that it would be 11hp which I doubt. I'm thinking with the right fire it will be around 6 to 8 hp.

That is around $900 in material cost. The center drum was 150. The coils which are eight 21' sticks of 1/4" pipe at $4 per foot totaling $672 and the end cap is $75.

Hi Bart,

I went Tom Kimmels' (Saca Pres) place two years ago and we wound those. He built a machine to do it, and he said he'd rather wind coils than eat . It's just a turn table and center post with a big gear reduction driving it. To control the feed and coil spacing the pipe runs through a vertical linear screw actuator/jack that the operator must crank in time with the rotation of hashmarks on the turntable (sort of like a human encoder). If it was mine I'd put a PC based CNC control on it. It's very powerful, it will wind 3/4" schedule 160 in to a 6" coil.

-Ron

[artemis]

Hi Wes,

I have no idea on the PPH. There is roughly 23 sq ft of water tube. Someone wrote 5 sq/ft per hp on a firetube and 2sq/ft per horsepower for a water tube. Judging by that it would be 11hp which I doubt. I'm thinking with the right fire it will be around 6 to 8 hp.

-Ron

The figure I've seen used in S&MSL as well as mentioned by several "old timers" is 5 sq.ft./HP for water tube and 10 sq.ft./HP for fire tube. This is, of course, a generalization and, as such, is subject to all sorts of variations, including "Finagle's Factor" to make it work.

[barts]

Hi Wes,

I have no idea on the PPH. There is roughly 23 sq ft of water tube. Someone wrote 5 sq/ft per hp on a firetube and 2sq/ft per horsepower for a water tube. Judging by that it would be 11hp which I doubt. I'm thinking with the right fire it will be around 6 to 8 hp.

-Ron

The figure I've seen used in S&MSL as well as mentioned by several "old timers" is 5 sq.ft./HP for water tube and 10 sq.ft./HP for fire tube. This is, of course, a generalization and, as such, is subject to all sorts of variations, including "Finagle's Factor" to make it work.

These number vary pretty heavily depending on the fire size and type, forcing, and the amount of heat one is willing to waste up the stack.

I know that if I use a stack blower and forced induction on Otter's boiler, I can more than keep up with the engine, but at a significant cost in fuel. I like to size things to simplify operation; I need to rebuild Otter's firebox to use fuel (oil) more efficiently.

There is little that is more more conducive to harmonious steaming than a simple sufficiency of water and steam.

- Bart

[DetroiTug]

More progress on the Ofeldt.

The upper and lower frames for the outer casing.

Top


Bottom


Lower pipe port for sight glass


Sitting upright


Upside down


This will have a square duct that comes out of the side of the casing at the top.

The top of this boiler will be against the top of the body which is wood. This should get interesting

-Ron

[fredrosse]

Nice work on the boiler, welding on the inside of the drum seems like a good way to go. It also looks like tubes are welded on the outside, but that weld would be difficult (at least for me) to make steam/water leak-proof.

The metal mounting frame, usually this type of boiler would be hung from the top, where the fire gasses have gotten down to a reasonably low temperature. Will the flames impinge on the lower support structure? I built a boiler that way years ago, and the carbon steel parts that got red hot only lasted about a week.

"There is roughly 23 sq ft of water tube. Someone wrote 5 sq/ft per hp on a firetube and 2sq/ft per horsepower for a water tube. Judging by that it would be 11hp which I doubt."

The old standard is 10 square ft for firetube, 5 square ft for watertube, so conventional sizing puts this at 23/5 = 4.6 boiler horsepower. Of course as mentioned above, one can force the fire for higher outputs, at the expense of boiler efficiency.

One boiler horsepower equals 33,475 BTU per hour to the steam output (30 PPH steam flow per horsepower output was the original basis for a "Boiler Horsepower", defined in 1876). In the range of a few horsepower engine output, typical simple non-condensing engines will require more than one “boiler horsepower” per actual engine output horsepower.