need help building a wood fired vertical fire tube boiler

[steampower88]

That will be a fairly large boiler. That is the size of my VFT-30 measured on the outside of the insulation and lagging. I believe the outside of the shell is 18". I have 2" of fiberglass blanket and then the wood. I can work my 3 x 4 simple engine rather hard without forced draft. You are getting close to 5 h.p. You can look at the specifications on the Beckman Boat Works site.

You will be able to squirt a lot of water up in the air.

Now is that a boiler that needs to be inspected on a regular basis?

[Lopez Mike]

Depends on where you live.

In Washington State, 'hobby boilers' are not inspected. We do have a club rule that to operate at any club event you must have your boiler inspected by a member of our safety committee. The inspection consists, first, of a hydro test to 1.5 times the safety valve setting. Then the the water is let down to the usual level and the boiler is fired up to the release point of the safety valve. Also the level glass is blown down to insure that it is working.

We have some other common sense requirements. All penetrations EXCEPT the safety valve must have a shutoff valve and the pipe between the valve and the boiler penetration must be at least schedule 80. Keeps you from kicking the stupid thing off accidentally. The entire subject is covered on our club web site.

http://www.northweststeamsociety.org/Pa ... safety.htm

Please download a PDF copy of our regulations. You will find it useful no matter what your local situation. These are MINIMUMS!

Not only do we not want you to blow yourself up, we don't need bad publicity.

[DetroiTug]

"I'd like to make it 24" by 30" tall not including the fire box"

That is the size of the boiler on my tug. It has water leg too though. Fired properly with wood, it will run a 3+3 X 4 twin at acceptable power output. Mine has 1.75" tubes, if I rebuild it I will use 1.25" tubes.

Consideration on water leg or absence thereof. Without a water leg allows another ring of fire tubes and also allows a larger fire. Which is better? Like many things related to steam, we may never know. Discussions regarding compounding versus single expansion engines - someone put it best with "the jury is out".

Looks like a great project.

-Ron

[Lopez Mike]

I have 61 1" flues each 15 inches long. I put turbulators in the flues and between that and running the water level up within maybe four inches of the upper tube sheet, I am not boiler limited with a 3 x 4 single and wood fuel. And believe me, I am a very indifferent fireman. Sort of throw it in there and hope not to have too many holes in the fire.

I would make your flues a lot shorter and use the height for a water leg around the firebox. Why heat up a bunch of refractory. Let that radiant heat get to the water.

If I were building my boiler to my own ideas I would do a buried tube boiler. Let all of the tube length be submerged.

A water leg boiler is really easy. You roll and seal weld the tubes into the tube sheets first. And THEN assemble the rest around that unit. If you try to deal with the tubes last, your welder will curse your name.

[TahoeSteam]

This project sounds very interesting... I'm a firefighter and have toyed with the idea of building a replica pumper as well.

Are you going to build a traditional engine or use existing castings and run the pump(s) in a different manner?

I second Mike's feelings on submerged tube VFT's. I understand Kingdon VFT's were very powerful for their size, aleit a bit more involvin the manufacturing process.

[steampower88]

I'd like to make it as traditional as possible, the biggest thing is I won't be able to use a "stock" crank because I need to fit two connecting rods in on the crank. One for the engine and one for the pump. I'd also like to build a channel iron frame for it. I've seen engines with this type of frame before and it looks nice. I'm glad a fellow smoke eater weighed in on this, it makes me want to do this even more. Can you show me pictures of a water leg boiler so I can see exactly what you guys are talking about? And thanks again everyone

[Lopez Mike]

Here's one guy's project: http://www.mysidewheeler.com/boiler.htm

I'll look around for a decent cross section diagram.

[steampower88]

Thank you very much for that link it definitely helped out with what you guys were talking about. That boiler seems like it would be perfect size as well. Now I've just got to find out how to build a engine.

[steampower88]

So as I'm getting with the water leg is that it's a inner ring that it is in the fire box with boiler water behind it. Not only would you be heating the base of th tubes but also the ring increasing your heating surface area considerably

[Lopez Mike]

That's correct.

Leave some clearance (1/16 to 1/8") at all places for the welder and there needs to be a bevel so that he can produce a full penetration weld. A good way to do all of the welds is to have the first seam done with TIG and then the rest with 7018 stick welding. This is pipe welding standard practice. Real welders will tell you about grinding out your starts and stops. If you don't know about these things you should probably get to know a welder with pipeline experience. Talk to the welder before you cut metal and follow the welders advice about details.

The easy way to build one is to have the upper tube sheet fit inside the main or outer shell. Recessed maybe a 1/2".

The lowest ring, or Mud Ring fits inside the outer shell (with welding clearance) and inside the water leg shell. Also recessed.

The lower tube sheet (at the roof of the firebox) fits inside the water leg shell (again with clearance).

So the only extra parts compared to a simple boiler are the mud ring and the outer firebox shell.

Easiest sequence is to cut all of your steel including the flues and the holes in the tube sheets.
Then assemble the tubes to the two tube sheets. This, when done, creates a very stiff structure around which to build the rest.
Next the outer firebox shell to the lower tube sheet.
Now the mud ring to the lower end of the firebox shell.
Next the whole mess is slid into the outer shell and welded.

You can trial assemble things as you go along. I do the fire door openings last. You rough them out with a cutting torch or plasma cutter. That might be good enough. This a good place for a big ugly hand grinder to make the holes in the firebox shell and the boiler shell fit the fire door assembly. I'm referring to the round or oval tube that goes between the outer shell and the firebox shell. The hole you throw the fuel through.

The rest are details that you will figure out as you go along. It's false economy to build your own pipe penetrations. The ready made ones are cheap and are the right things to use.

I firmly recommend that you have the welding done by an experienced person. If they start out by making fun of things like grinding out welding starts and stops and such, quietly walk away. When built right, tested and maintained these are bullet proof units. Make serous errors and you can get killed.

The rest of the crowd will add much to these instructions. There are other ways to do things. Most of them are fine but do follow any advice that affects safety.