The Steamboating Forum

I am considering construction of a vertical fire tube boiler with tubes 15” long. I am considering 1” o.d. steel tubes, and will be burning wood for fuel on natural draft. Can anyone speak from experience as to whether problems from tubes becoming clogged with soot and ash are present with tubes of this relatively small (.810) inside diameter at this length?

I had a VFT with 1 inch x 0.095 tubes, 24 inches long in home heating service (hot water heat, 100F - 160F). This burned wood, ran 24-7 in the winter, and I wished it had bigger tubes. You would probably have better combustion than this setup, as the fire was not tended as well as a steamboat boiler would be. Soot would accumulate, and the tubes needed brushing every two weeks, and I am sure the efficiency was getting bad in just a few days. If you use such small tubes, be sure you have decent access for brushing the tubes.

Also check that you have ample flue gas flow area, as a small thickness of soot will seriously impede draft much more for small tubes than for larger ones. On this heating system, I had the advantage of a stack 20 feet high, but draft did get sluggish after a couple of weeks use.

The next VFT I had used 1-1/2 inch x 0.125 tubes, burning anthracite coal, again running 24-7 generating 150 PSI steam. These tubes were probably a bit too large, and a steam soot blower was able to keep the tubes fairly clean. The anthracite ash was much easier to blow away than the wood soot buildup.

My next VFT, which currently supplies steam in the sidewheeler, has as you might guess, 1-1/4 x 0.095 tubes, 18 inches long. I had planned on wood/coal/coke firing, but in the rush to get going I just used a Propane weed burner, and so I have no experience with soot on this boiler. I like the propane so much I am most probably going to stay with it.

Kelly Anderson wrote:I am considering construction of a vertical fire tube boiler with tubes 15” long. I am considering 1” o.d. steel tubes, and will be burning wood for fuel on natural draft. Can anyone speak from experience as to whether problems from tubes becoming clogged with soot and ash are present with tubes of this relatively small (.810) inside diameter at this length?

As I recall Semple used 1.25" in their boilers and had no problems. The 15" length should be about right.