Boiler

2008 - 2009.


John R. Bentley 2009.

Model Watertube Boiler

-  Forming the Boiler Drum Heads  -



 
Some wood from a downed Flowering Crabapple tree across the street
 
 
 
 
Applewood is a nice close-grained wood
 
 
 
 
Starting to turn a form on a Craftex mini lathe in the shape of the steam drum heads
 
 
 
 
Checking for the required curve with a cardboard guide
 
 
 
 
Now for the female side of the form
 
 
 
 
Good fit!
 
 
 
 
Both parts for the upper drum heads
- beeswax applied
 
 
 
 
Making flat sheet from copper pipe - sacrilege!
 
 
 
 
 
 
The longitudinal cut
 
 
 
The 4x6 bandsaw blade rips nicely through the top with novel use of a large C-clamp

 
 
 
 
The gap of the sawcut shows the amount of stress relieved after twenty-five years of being a tube!
(this is similar to how I feel when getting out of a plane after flying to the UK from here)
 
 
 
 
Cookin' with gas
 
 
 
 
I just love annealed copper!
 
 
 
After annealing it unrolls by hand almost as soft as a sheet of lead
 
 
 
 
Dead-blow mallet full of lead shot
 
 
 
 
This scrap disk just happened to be the right size to act as a pattern
 
 
 
 
Those little 4x6 horizontal/vertical bandsaws are great!
 
 
 
 
Ahhh - finally - the thick blank is ready for forming!
 
 
 
 
Squeezing the blank between the applewood forms in the vice
 
 
 
It worked!
 
 
 
 
A dished head prior to forming the circumfrential flange
 
 
 
 
This job took a half-dozen annealings for each head
 
 
 
 
 
 
 
Beginning to bend the flange around the form using a soft hammer
 
 
 
 
 
A nice clean job straight out of the form - prior to fitting and surface finishing
 
 
If anybody thinks this head is too thin, I think they're nuts!
 
 
 
 The drilled head and threaded phosphor bronze ferrules (bushes)
 
 
 
 
All ferrules held in position ready for brazing
 
 
 
 
Brazed from the inside - just to be sure!
 

The silver alloy fillet around the pipe flange (outside bottom) is not required
(some of the brazing alloy simply ran down by gravity during the job)

 
 
 
The finished front head for the steam drum
 
 
 


These are similar forms which were used to make the small heads for the lower drum
 
 
 


A polished lower drum head in position prior to silver brazing

 


 
 
 
Pressure Vessel Brazing -  Timeline (2009):


Convection bank 

      The first row of straight tubes was brazed into the drums on Feb. 22

      Second and third rows were brazed in on Feb. 23

      Fourth (last) row in the convection bank was brazed into position on the 24


Radiant section (furnace)
 
      First of the curved D-shaped rows went in on Feb. 26

      The final row of tubes (outside curved row) was attached Feb. 28

      Subsequently the viewport cooling loop was separately attached
 
      Drum heads were formed then various screwed ferrules were brazed to the top front head and the two drums.

      The heads were individually brazed in place during four separate sessions on Mar 25 & 26
 

There were about fifteen separate heating sessions required to braze the pressure vessel. In addition 25 anneals were preformed while forming the four drum heads.