Are water-tube boilers actually easier to build?

[Lopez Mike]

Better you than me.

I'm quite attached to lighting my little wood fire and listening to the quiet noises it makes as it comes up to temperature.

Who knew that an electromechanical engineer like me would be such a luddite?

As I write this I'm sketching out the designs for several uP based designs. A replacement for my ancient hot tub controller. New insides for my variometer that I use for paragliding. An impedance bridge for ham radio antenna design.

But nothing for my boat, thank you.

Hm. What's that in my tool kit? A VHF radio. A GPS. A bicycle speedo tach. Yaaaa!

[barts]

Better you than me.

I'm quite attached to lighting my little wood fire and listening to the quiet noises it makes as it comes up to temperature.

Who knew that an electromechanical engineer like me would be such a luddite?

As I write this I'm sketching out the designs for several uP based designs. A replacement for my ancient hot tub controller. New insides for my variometer that I use for paragliding. An impedance bridge for ham radio antenna design.

But nothing for my boat, thank you.

Hm. What's that in my tool kit? A VHF radio. A GPS. A bicycle speedo tach. Yaaaa!

I think a long strong recip pump running at 120 rpm or so won't be too noisy... and a wood fire is definitely in the cards; I have little interest in listening to a oil burner other than as a backup.

- Bart

[hartleymartin]

I have some previous experience with methylated spirit and kerosene burners. I do understand that the truth of the matter is that fire-tube boilers are easier to fire than water-tube boilers, in particular when burning coal or wood because you have a large steam-reserve which allows you to build up the fire and steam pressure. On the other hand, the water-tube boiler has a fairly small steam reserve, it can make steam quickly, but is much more sensitive to changes in steam use and in the fire.

Who knows? I might acquire a used unit cheaply enough. It's nice to dream about it.

[DetroiTug]

I have some previous experience with methylated spirit and kerosene burners.

I would be interested to know your experiences with vaporizing kerosene in another thread (Anoraks corner if it cannot be applied to boats). I've been working on a kerosene vaporizing burner for about a year off and on with less than optimal results. I could switch to gasoline/petrol which is very easy to vaporize, but I'm stubborn. I like the added safety feature (lower flammability) of kerosene. I can get it to work, just not reliably. The problem lies in stable vaporization.

-Ron

[barts]

I have some previous experience with methylated spirit and kerosene burners.

I would be interested to know your experiences with vaporizing kerosene in another thread (Anoraks corner if it cannot be applied to boats). I've been working on a kerosene vaporizing burner for about a year off and on with less than optimal results. I could switch to gasoline/petrol which is very easy to vaporize, but I'm stubborn. I like the added safety feature (lower flammability) of kerosene. I can get it to work, just not reliably. The problem lies in stable vaporization.

-Ron

I ran a vaporizing burner on my old boiler... it was a pretty classic design, with a 1/2" NTP pipe full of metal screen wrapped around a 1/4" steel rod going into the boiler, and then a pipe going down about 4" and a 1/4" piece of pipe w/ three or four small diameter holes coming back out - a horizontal U. A pan beneath the burner would take a rag and I'd spill in some kerosene (the burner was supplied by a automotive fuel pump at about 3 or 4 psi). Light the rag, and just crack the fuel valve... the spitting would stop after a while and the burner would... burn. I didn't have enough clearance between the burner and the tubes, so the whole mess tended to be rather sooty, but this did work for about several years until the (ancient used) boiler developed a pinhole leak in one tube; I managed to fix this but the handwriting was on the wall and I started building my current boiler.

- Bart

[Lopez Mike]

Unclear.

Was the 1/4" pipe with the holes underneath the 1/2" pipe with the internal screen? That is, did the flame coming out of the hole heat up the incoming fuel in the 1/2" pipe?

There are days when I desire to steam further afield or when towing Folly to some place where wood is a bit harder to come by than my back yard, that just filling up a fuel tank with light oil sounds doable.

I'm wondering how I would arrange the burner with my VFT so that the flame was distributed well.

Up until now I had been only looking at paint sprayer conversions or droolers.

[barts]

Burner looked like this:

Code: Select all

    Kerosene () in: ->                          ===================================+     <- 1/2" pipe filled w/ screen
                                                                                  |
                                                                                  |
                                                ------^---------^--------^--------+       <- 1/4" pipe w/ jets (.060 or so)

                                             \____________________________________/   <- pan 

You could make a round one w/ too much trouble if you can bend pipe in a circle after putting in the screening.

<ascii art in variable width fonts is a PITA>

I remembered after posting that I'd also welded a piece of 1" angle w/ the V pointing down to the 1/2" pipe as a flame spreader... some experimentation will be required, but the first one I made worked. Don't omit the screen - it prevents surging and shooting burning liquid out of the holes !

[Jack Innes]

I have actual experience with the type of burner mentioned here. This in its original form ran for many years with success.
I have completely rebuilt the power plant of this boat & have now fired the burner several times with good results. Full flame is achieved at 5 minutes & at 10 minutes I have steam at 90 psig.

There is a pan under the burner with several rows of stove door gasket rope, you add about 4 oz of alcohol to the tray to preheat the burner. Once a little heat is present open the needle valve controlling the fuel intermittently until a vaporised burn is heard - like an old blow-torch. Then the flame can be regulated by the needle valve quite finely.

The upper pipe is 1/2" iron pipe, the lower one is 1/8" iron pipe, the jets are common brass npt plugs drilled with a no. 58 drill. The jets can be replaced or altered larger or smaller easily. The upper pipe is stuffed with copper wool from a scouring pad. I am sure screen would work. The pipe fittings are tack welded to prevent movement.

I remade the deflector to more effectively direct the flame away from the ends & up through the coils of the Blackstaffe boiler. The picture with the burner in place shows the new deflector design. For reference the boiler casing is 18" long.

The fuel system consists of two garden sprayer tanks. The starting tank carries Varsol/paint thinner to burn cleaner until everything is warmed up. The main tank carries kerosene as the primary fuel. The fuel tanks are pressurised by 2 air tanks initially at 120 psig & regulated to 15 psig. There is a 3 way selector valve to choose the tank in use or turn all off.
The hand pumps are still in the fuel tanks as a back up in case of total pressure loss.

In the mock up picture you can see a rectangular hole in the end assembly. Both ends have similar holes that supply the needed combustion air. Both holes are located so there should be no chance of wind, etc. having any effect.

The burner is held in place by a single clamp around the brass inlet fitting.

[Lopez Mike]

More questions:

How much noise does it make? I know, "Compared to what?"

Alcohol and kerosene are exotic things around fuel docks. What are the chances of heating it up initially with a plumbers propane torch and running it on 'diessle'?

How big of a power plant were you running with this burner?

[barts]

More questions:

How much noise does it make? I know, "Compared to what?"

Alcohol and kerosene are exotic things around fuel docks. What are the chances of heating it up initially with a plumbers propane torch and running it on 'diessle'?

How big of a power plant were you running with this burner?

I used a fairly low pressure and larger ports IIRC; it was pretty quiet - much quieter than the steam atomizing sort.
I've never seen anyone run these burners successfully for any length of time on diesel; they coke up and the holes plug.

I ran a 2x2 engine, but these things scale up really well. Much bigger engines have been run on these sorts of
burners - Alan Amerian ran his 27' piece of floating furniture with one of these.

A more adventurous sort might attempt a true carburating burner ala Stanley steamers; I experimented with this
a little but was not successful in getting a properly consistent vaporization, and I'm unwilling to use part gasoline as Stanleys do.

A burner design that I feel could use more experimenting is a pot burner ala a diesel stove. These don't lend themselves to working with wood fires, but the design is very simple to fabricate (if tricky in the proportions) and very quiet. Many household oil stoves used this burner, as it can be gravity fed, needs no electricity and is simple to maintain with no small orifices, etc. A big pot burner could be a natural fit for a VFT boiler.

- Bart