2008 - 2009.
John R. Bentley 2009.
Model Watertube Boiler
- Tubing the Pressure Vessel -
First row of tubes in the convection bankProgress to March 17:Second row - still dirty from brazingSlightly curved tubes for the third rowPutting them in, prior to brazingPretty flux job, huh?Fitting the final (fourth) rowFourth row - ready for brazingDone! 4 rows brazed - convection section completedSo far I am pleased with the jointsChecking out one of the deep-curved tubes for the furnace sectionNow ... the D-tubesFitting the inner rowView showing a single tube from the outer row filling one of the gapsThe D-shaped furnace section is starting to take shapeThe question here is how to keep them all flush during brazing...An idea is hatched:I will use two angle pieces made from soft copper to squeeze the C-shaped tubes into one plane.These copper angle pieces were formed in the viseThe clamped angle pieces "sandwich" the straight sections of the tubes for alignmentEnd viewClamps removed and the steam generator is still almost red hot after the brazing sessionTemporarily putting short lengths of tubing into the gaps to act as spacersThe outer row of furnace-wall tubes (not yet brazed in)- together the two rows will create a solid waterwallChecking to see if it is flushCitric Acid pickling after brazing the outer tubesOuter furnace row of brazed jointsViewing the fireThere is a viewing porthole in the back wall of the boiler enclosure...This bifurcated tube surrounds that port, absorbing excessive heat near the glass.Here's a view of the window cooling loop brazed in positionLooking from the firehole end(note the window is located below centre - otherwise only the end of the burner would be visible)Drum internalsEnd view of deflector baffle assemblyIt's made from copper pipe and is silver brazed with a higher-temperature alloy(to prevent a meltdown when the heads are brazed in)Baffle unit's position in the upper drumLooking upward, showing upper right deflector position, relative to uppermost tube endsMaking the steam outlet for the collector pipe unitSome of the 54 steam entry holes positioned across the top of the collector pipeThe collector pipe assembly (holes on top not visible)The collector pipe will be screwed into the phosphor bronze ferrule and silver brazed in position at the top of the boiler steam drum. The ferrule (bush) will comprise the main steam outlet of the boiler.Collector pipe mounted in position between the upper deflectorsSteam entry hole locations along the top of the collector pipe are skipped directly below the safety valve openings to avoid being located in extreme low pressure areas when the valves open and the possibility of water being carried over into the outbound steam.Bronze ferrules (bushes)Sawing up some more phosphor bronze to make threaded bushes for the smaller fittingsMaking the smaller piece roundFinished threaded bush for the main steam outletIt is extra tall so it will be be flush with the roof of the boiler casing (allowing for the thickness of the insulation)I will position the tops of the two threaded bushes for the safety valves below the roof of the boiler casing (at the level of the drum the drum). This will allow some extra hidden length for the valves. With only the upper portion of the safety valves visible, they can be made to appear closer to scale in appearance yet function properly without hindrance due to extra space within.A fistful of copperI'll be glad when the drum heads are attached and the vessel has been pressure tested. I went out for more citric acid, silver brazing alloy, propane and steel wool today - so I should be ready!The phosphor bronze ferrules, brazed into the top drum(blanking plugs screwed in)
That's all the tubes brazed in place...the drum heads are next.
NEXT: Part 5
Forming the Drum Ends