From napkins to fabrication VFT boiler design

[Spanky]

Hello Again Everyone,

My Red hardcover steam bible finally came! But that's a different story. I've got an update to my steaming dreams. I've decided to go with a Stanley type VFT boiler instead of using a water leg. A couple reasons being that the Stanley type will be so so sooooooo much simpler for me to construct. The Stanley will also be lighter and will allow me to swap out the grate in the firebox below it to switch between coal burning and wood burning if I so choose. (or at least I hope that's all I'd have to do)

So the specs so far...
18" OD shell, 13" tall, with a 3/8" wall
55 A178 Tubes, 1 1/2" OD, 13" long
Top and bottom plates 3/8" thick
Tubes are 1/2" apart wall to wall

Tubes are in the equidistant hexagon pattern (still not sure of the proper name for this shape, I'm sure it's in this very thread somewhere...)

I calculated about 23 sqft. of heating area, and about 1/2 sqft. of gas flow area through the plates.

I'll post pictures when I can.

Thanks all,
Josh

[fredrosse]

"Tubes are in the equidistant hexagon pattern (still not sure of the proper name for this shape, I'm sure it's in this very thread somewhere...) "

In the Heat Exchanger world, that is called "Equilateral Tube Pitch"

Your tube spacing allows at least 0.65 inches from a tube to the inside of the boiler shell, that is good as it is enough room for the weld of tubesheet to shell without being too close to the tube.

[Spanky]

Here's a list of planned fittings and their locations (all are 1" weld o lets or pipe couplings)

Safety valve: Coming out of the top plate.

Main steam: Coming out of the top plate. (does anyone have a picture or description of how to make the separator pipe used to prevent priming the engine?)

Pressure gauge: Not sure about this one... is coming out of the side of the shell near the top plate the correct location?

Sight glass top fitting: Not sure about the distance from the top plate but 1 1/2" from the plate to the fittings axis seems like a good distance.

Sight glass bottom: Again not too sure about this distance but 2" seems good. Water would be absent from the glass at 3"-3 1/2" from the bottom plate.

Feed water in: I'm fairly certain the optimal location of this fitting is already given somewhere on the forums, but I could be wrong.

Blow down: Just wondering what kind of valve to use for blow down, I read in "Steamboats" that globe valves are frowned upon as a piece of scale could jam the valve open. Are gate valves used in this instance?

Whistle: again coming out of the top plate. If I ever decide to switch to a condensing system this will become my auxiliary steam for whistle, stack blower and maybe an injector.

And just a side note, I may have found a boiler tube supplier Anderson Tube Co. out of Hatfield PA. I haven't contacted them yet but I will when the design is all finalized and I have my friends dad (former boiler inspector for Wisconsin) give it a look. Here's their website for those interested. http://www.atube.com/boiler_tubing.htm

Josh

[Spanky]

I finally got around to making a picture.

The upper left black arrow indicates fore the lower right arrow aft.

Fittings are as follows.
Safety valve: Yellow
Main Steam: Red
Pressure Gauge: Pink
Sight Glass: Dark blue (2x)
Feed water: Sky blue
Blow down: Brown
Whistle: Green

What do you all think of the general placement?

Josh

[fredrosse]

Separator

[Spanky]

I was actually wondering if there was one that fits inside the boiler. In "steamboats" there is an illustration of a perforated pipe. If I replaced my center tube with this would it work? I don't think much sloshing of the water occurs at the center

Josh

[fredrosse]

A perforated horizontal pipe, mounted high in the steam space (called a Dry Pipe) is used on many traction engine boilers and similar horizontal shell boilers. I have not seen them on a Stanley type VFT boiler.

[gondolier88]

I thought Stanley boilers were designed as flash boiler, so a piccalo pipe (UK term) would be unnecceasry on a Stanley boiler of conventional use as they would have no water to carry over.

Greg

[DetroiTug]

The early Stanley and Locomobile boilers were firetube with piano wire wrapped around the shell. Bourdon Boiler works sells new ones. I couldn't find a website for them.

-Ron

[artemis]

Frank Graham of Audel's fame designed one for VFT - it was in the form of a circle a little less than the inside diameter of the boiler, placed near (within an inch of) the top and with the holes drilled in the top of the ring. It was half again the size of the main steam line and served it only. I've also heard of them used in rebuilt/new build stanley boilers but not favored as the high water/vigorous-motion-of-the-automobile still caused some water to be carried over. I would guess that if the water level were 6" or so below the top of the boiler this might not occur on a boat. Also if the main steam line were located at the after end of the ring to prevent water-surging within the ring from entering the main steam line??? In large ship installations where motion was slower and less violent this might not be a problem.

Info on Bourdon Boiler Works (from SACA Bulletin):
Bourdon Boiler Works
P.O. Box 55
Woodstock, VT 05901
Tel: 802.457.3787
email: bboiler@comcast.com