The Steamboating Forum

I talked with Jeff Lund tonight about the "separable base with ash pan"/air intake/cleanout part is one of the last things he's going to make as it's not even part of the ASME certification of the pressure vessel.

A lot of you both in this forum and offline have suggested that 6" ash pan door is way too small, maybe double it.

Even though it's late in the game as Jeff has already been cutting steel, he is flexible on the separate assembly.

Jeff and I came to an agreement that I have at least 1 week to tell him how I want the ashpan door(s).

He has agreed to make at least 2. 6" up to 18"(Although he thinks 18" is starting to compromise the structural integrity of the base which has to support the boiler).

So folks, without doing heavy calculations, what angular orientation and sizes for 2 ashpan/draft doors between 6" up to 18" for this boiler would you recommend?

-CB

If there is a frame around it, I don't expect there will be a structural issue supporting the weight of the boiler.

I'm not where I can measure mine this week but I would estimate that my ash door is 4 to 5" high by 12 to 14" wide with a door hinged along the top edge. I find that there is little extra air flow to be had beyond about 70 degrees of opening. It tends to stay wherever I set it due to rust and crud in the piano type hinge. What can I say? It works.

Oh yeah. It's a Beckman VFT30 rated 4.5 h.p. with 33 sq. ft. of heating surface. I have no idea of the grate area.

It may be large enough to supply the required air, only way to know is fire it up. Exhausting up the stack (inducing draft) is going to change it all. One cannot have too much draft air on a wood fire, but can certainly not have enough.

The real issue with that size is the matter of removing ashes, that door as it is, is too small. A shovel is used and there would be no easy way to clean out to the immediate left and right of that opening.

Taking out ash is important. We burn a lot of wood and as soon as the ashes are taken out even if they aren't near the grate, a substantial increase in power is noticed. My theory is that when the fire is drawing hard the ash is being drawn in to the fire and extinguishing the combustion. We take ashes out frequently.

It needs to be 4" X 12" at least.

-Ron

Hooo! I never thought of the ashes being drawn in. Maybe I had better clean things out more often than once a year.

Another reason for a large ash door is access with the rather fat hose from my shop vacuum. On a dead boiler mind you.

I've been experimenting with a stack blower and recently managed to drop a hot cinder on a passenger wearing some sort of plastic shirt. Melted a little hole in it and gave him a teeny burn. I hate to restrict the draft in any way and I suspect that any stack screen that would stop a cinder would soot up.

Lopez Mike wrote:I suspect that any stack screen that would stop a cinder would soot up

Absolutely and in short order. I have a Canvas walltent with a wood stove and per the USDA? requirements it has to have a spark arrestor. It's simply a cone of hardware cloth with 1/4" spacing. It has to be cleaned every day or it becomes clogged. How this was learned was on the second morning of our hunting trip, we woke up with the tent full of smoke. I was never so glad to be awake.

-Ron

I've been think for a long time (typical) of installing turbulators in my flues. Twisted strips of flat sheet metal hanging down in each flue. I see one hanging down in the flue in my RV propane fridge. I've heard good things. I suspect that it will mean yanking them out regularly to clean them off. Not a problem for me as I have easy access to the top tube sheet of my boiler.

I wonder if the turbulence induced in the flues might cut down on the sparks coming out of the stack at high firing rates? I guess I'll know when I get around to it.

VFT boilers on steam donkeys were suported at four points by angle brackets on the outside of the water legs that transfered the weight of the boiler to the donkey frame. The ash pan fit between the I-beams of the frame did not support the boiler. On a boiler 3.5ft in diameter the ash pan door was around 6" x 18" and provided with a damper for draft control. That said, for all the reason given before, I'd go for a large door since you can easily slow down the draft with a damper, but there's not much you can do if the fire is starved fir air because the door is to small.

Dave

From Jack; "Without any real testing it seemed that more heat was sent to the radiators with the turbulators in place."

On my VFT I did some real testing, and the turbulators cut my fuel consumption in half! I would not expect such a drastic advantage for a wood/coal or oil fired boiler, because I burn Propane which inherently has a much diminished radiant heat transfer character. Three features allowed the performance improvement: 1. The turbulators become red hot in the bottom of the tube, and therefore allow significant radiant heat transfer to the tube wall. 2. The turbulators break up and mix the hot gasses from the burner with the relatively cool gas hanging near the tube inner wall, increasing heat transfer. 3. The turbulators restrict the flow of excess air from the firebox to the stack, less excess air causes higher flame temperature.

Burnimg gas keeps all of this very clean, and firing other fuels will eventually restrict flue gas flow as the turbulators soot up. For the soot laden fuels, regular cleaning of the tubes, and turbulators is required.

I have flat twisted strip turbulators in my boiler and they definitely help. Without them there is laminar flow where the hottest gases travel through the center of the vertical tubes. The columns are hottest in the center and then layers of cooler air toward the walls.

I try to burn only seasoned wood and with also exhausting up the stack, when I clean the flues there is very little soot. It must be drawing fire up near the top of the tubes and burning it up. I get lots of ash on the top tube sheet, but that's it.

Apologies as we've sort of taken this thread off course, but these are all considerations for your new VFT boiler.

-Ron