Part 24: More boiler work—April–May 2002
Finally, after the squeezing of the foundation ring, the last major piece of welding was able to occur. This was the fire box tube plate. Once this was in place, and most of the welding done, it was close to time to put the boiler back up the right way.
We are finally getting to a point where progress will appear to be accelerating, simply because most of the work that has to be done in serial fashion is complete. Just prior to "flipping" the boiler over (in the trade, big items always seem to be "flipped" as if they were the size of a dollar coin!), the throat plate stay holes were reamed to final size, and threaded. This enabled the installation of the stays that had been in store for some months. The final upside down jobs”were the fitting and tacking together of the grate support angles and the ash deflector skirt, and caulking of the firebox copper plate to the foundation ring.
The boiler was then duly flipped, enabling easy completion of the tube plate welding.
Whilst this was occurring, the boiler tubes were taken out of storage to be readied for installation. The superheater flues were trimmed to length and put out side to have their ends annealed. The small tubes (which had been swaged down at the firebox end and cut to length at Quorn many months ago were also got out. Two of these were placed in the boiler to help provide a shelf to support the portable boring device required to open up some of the fire box tube holes. Super-embarrassment when we discovered that these tubes were about an inch short. Length was according to drawing, but not according to boiler. Not sure what happened, but it seems like there might have been a bit of dyslexia when writing down the measured length last year, causing the right dimension to be written down wrongly, and then discarded as being wrong, causing reversion to the drawing. Whatever the reason, it had to be fixed, so a piece was cut off each tube, and a slightly longer piece welded on. Sometimes when you make a mistake you pay once. Here we paid 70 times!
Current state of progress is that the re-ending process is well advanced, most tubes have been annealed, and about half the superheater flue tubes have had their ends polished. The throat plate stays have been seal welded, and it remains only to weld in one bush (for the pressure gauge connection) for weld repairs to be complete.
Because some of the tube plate holes are close to the weld line, it was decided to cut these (in the case of small ones), and open up (in the case of big ones) after installation. This was accomplished easily on the smoke box end using a magnetic base drill for the hole making. Four of these holes had to be taper tapped for washout plugs. Here a support was tacked to the smokebox ring to guide the tap, and a ratchet spanner in concert with a long piece of pipe did the screwing. Opening up the super heater flue holes in the firebox tube plate has commenced using our homemade air powered boring machine. It is a bit of a grunt to get into position, but is doing a satisfactory job.
While all this has been going on, work has commenced on cleaning up the mounting faces for the various boiler fittings. Installation of the tubes is now only a matter of hours away. That means it will be hydraulic test time very soon. We are keeping our finger nails long for biting on!