REFURBISHING THE BOILER
The millwrights take over
As typical with any machine, the boiler of a locomotive requires periodic maintenance. The 3 main issues with boilers that need constant attention are;
1. Distortion caused by the heat expansion coefficient. This coefficient causes staybolts and rivets to loosen and start leaking.
2. Buildup of soot in the firetubes. The soot acts as an insulator requiring more fuel to boil the same amount of water.
3. Scaling, the buildup of chemicals left behind as water boils.
These are standard procedures that are conducted when a locomotive is in operation. However when a steam engine goes dormant for 30+ years, other issues pop up such as rust from water, corrosion from leftover soot and hidden stress cracks. The entire boiler had to be prepped for ultrasound. All equipment needed to be taken off. The picture to the left is the cab after being stripped.
Inside the cab in 1967 Karl Hammerstrom photographer
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Once the test was completed we were able to verify that the boiler shell was in good condition and able to handle 200 psi. which was the original pressure the vessel was designed to produce. We discovered some rivets that could potentially leak and replaced them. These brackets helped hold the tube sheet in place while under pressure.
Now that the rivets were repaired we could replace the firetubes.
This is an interior view of the boiler vessel looking toward the rear tubesheet which joins the firebox. The large pipe above is the main drypipe that gathers the steam from the steamdome. The throttle valve (not seen) is located at the end of the drypipe which controls the amount of steam as the engineer chooses.
The white arrow in the upper left is pointing to a staybolt.
This view is looking at the front tubesheet. The main steampipe exits into a manifold that redistributes the saturated (wet) steam into the superheater tubes to be reheated into superheated (dry) steam.
This view looks to the rear tubesheet from the firebox. The firebox is totally surrounded by water because the heat of the intense fire inside this box has the potential to melt steel. The cylinder shape of the boiler vessel distributes the pressure evenly and safely contains it. However, the rectangular shape of the firebox can be crushed if not for staybolts joining the firebox crownsheet to the boiler.
The crew installing one of the larger diameter firetube to the front tubesheet.
To the left, after the firetubes are installed they need to be rolled to seal them and secure them to the tubesheet.