I welcome any and all discussion on why a "water tube boiler" is not a good idea. Yes we are working to get the unit ASME rated and stamped for 30 PSIG, welding is accomplished by an ASME certified welder. Unit uses one of our existing grates so is a Rice/Buck coal burning appliance. Flue outlet is 6" for this unit, future larger units will have 8".
Keep the comments coming, of course I do understand that design review by committee based on a few partial completion photos is an entertaining concept at best, but we do like to stir up the discussion and thought process. Thanks.
I am not sure you will enjoy my jaded comments regarding this design. So let me answer your quest for discussion on water tube boilers with a question. You have been kind to my questions and comments - I think I may skirt your patience if I vent mine - well here goes.
---> have you ever had to tend one? ( a water tube boiler ) <--
While a water tube is safer and quicker to bring on line/recover when operated as a steam boiler ( less surface area to explode) - if you ever had to crank your upper body into one and clean the outside of the water tubes that run in the fire box -- well you will find something else to do next time. You cannot weld in enough clean out doors and access to ever make that job palatable. Here is a episode of "Dirty Jobs" for sure. You will not want to do it a second time.
Second thought -- think about what happens in a fire tube boiler if a tube fails. Water moves to atmosphere right -- the vessel simply leeks slowly to the outside in only that failed tube - You find it immediately in daily tending. To repair, you simply drive a tapered hardwood plug into each end of the broken fire tube and the system keeps running. Often you can do this because each end is accesable via doors for flue punching and ash trap boxes and the vessel never has to go cold. Repair is done in the off season.
While its possible to also plug a water tube, first you have to determine what tube has fractured - that will not be apparent until the leek is enough to severely curtail or put out the fire -- then the boiler must be taken off line - drained of water - well by this time you may as well roll a new tube in -- do you have a back up?? or has the load gone cold now? This (water tube) is the thinnest part of the vessel and now the thinnest part has fire impinging directly on its surface --
I can go on --- well maybe I better not
NOPE -- no water tube boilers for me now or my next life time thank-you.