With the hydro test successfully completed, 1385’s boiler has received a shiny coat of paint on the boiler exterior and it looks great! Most of it will be covered later though by lagging (insulation) and boiler jacketing.
C&NW 1385’s new boiler – painted and ready for delivery. Photo courtesy Continental Fabricators.
The smokebox has also been attached for shipment. The smokebox has only been tack welded in place as it will need to be detached later. It will need to be attached to – and become part of – the cylinder saddle first. Then the boiler is attached to it.
Front view of 1385’s boiler with smokebox attached. Photo courtesy Continental Fabricators.
Sharp-eyed viewers will notice in the smokebox door ring has been bolted in place upside down. It has just been temporarily fastened in place and it too will be removed and re-added probably multiple times before the locomotive is completed.
With this, the work at Continental Fabricators is complete. Now the boiler will join the cab and running gear at SPEC Machine in Middleton, Wis.
PLEASE NOTE: We appreciate the public’s enthusiasm to see the 1385’s progress first-hand; however, the contractor shops where the #1385 work is taking place are private property and not open to the public. Anyone requesting to see the locomotive at those locations will be turned away. Please help #1385 return to operation as expeditiously as possible by respecting our contractors’ wishes.
This is our 100th C&NW #1385 steam status update posted to our website and it is a momentous one! The locomotive’s new boiler has passed its hydrostatic test (a.k.a. hydro test). This test affirms the new boiler remains sealed with no leaks while at pressures well in excess of its designed operating pressure.
Pressure gauge showing 300 PSI during 1385’s hydro test. Photo courtesy Continental Fabricators.
This test is conducted by filling the boiler to the point there is no (or practically no) air trapped in the boiler. Additional water is then pumped in until it reaches the designated test pressure – this can require as little as a few cups of water. Excluding the air allows the boiler and appurtenances to be safely tested for. If a leak appears the pressure quickly drops by relieving that cup or two of water.
To complete the test, the boiler is then left under pressure for a period of time. An inspector then checks to see if the pressure has dropped. If the pressure has gone down more than a few percentage points, it indicates a significant leak which must be tracked down and corrected. If the pressure does not see a drop by more than a few percentage points, it indicates there are no significant leaks and it passes the test.
The 300 PSI you see on the pressure gauge is 1 ½ times the designed maximum working pressure of the boiler. This is one standard benchmark percentage for testing and helps prove the boiler has a margin of safety when in use. The 1385’s boiler has been designed for a maximum allowable working pressure (MAWP) of 200 PSI with a minimum safety factor of four. This means the boiler is designed to withstand pressures of at least four times greater than the MAWP which you can see gives a sizable margin of safety when in use. The 200-pound pressure also marks a return to the R-1 class locomotives’ design pressure, meaning the engine will be restored to its original capabilities.
C&NW 1385’s boiler being fed water as part of the boiler’s hydro test. Photo courtesy Continental Fabricators.
Closer view of the finished tube work. Photo courtesy Continental Fabricators.
Up next: Prepare and attach the smokebox and paint the boiler exterior.
In this C&NW #1385 update, we get a glimpse of the process of installing tubes in the boiler.
The tubes are installed by sliding them into the holes on the tubesheet. Their outside diameter is just slightly smaller than the holes in the tube sheet. However, in order to have a water-tight and steam-tight seal, there can’t be any gap. This is achieved through a process called rolling.
In the rolling process the tube is actually expanded from the inside using a roller. The roller presses the end of the tube against the hole in the tubesheet tightly enough to form a steam-tight seal. The end of the tube actually sticks out of the hole a specified amount. The portion that sticks out is then curled outward and back until it touches the tubesheet in a process called beading. If the end of the tube were left hanging out by itself it would soon overheat and burn off or crack. Since the beaded end of the tube is touching the tubesheet it will transfer some of the heat back into the tubesheet and not get hot enough to burn off or crack.
A Continental Fabricators employee trims excess tube material from the front of the boiler. Additional employees are on the firebox-end rolling and beading the tubes. Photos courtesy Continental Fabricators.
Additionally, the arch tubes have now been installed. Arch tubes provide increased firebox heating surface area and allow better circulation of water in the areas surrounding the firebox. The arch tubes also serve to support the brick arch, a series of firebricks that help direct heat from the fire more evenly throughout the firebox.
Arch tubes inside the 1385’s firebox as viewed from firebox door. S. Roudebush photo.
Wrappersheet around the firebox showing the stays, arch tube plugs and the external combustion air inlets S. Roudebush photo.
Detail view of wrappersheet showing the stays, arch tube cleanout holes (with plugs removed) and the external combustion air inlets. S. Roudebush photo.
With the tubes now installed, a countdown clock has begun to tick. A boiler must be disassembled for extensive Federal Railroad Administration mandated inspections every 15 calendar years or 1,472 days of operating – whichever occurs first. Once the first tube was installed, the FRA gives a 1-year grace period in which to complete work before the 15-year time limit begins. If the locomotive is completed in less time, the 15-year clock starts once the FRA accepts the locomotive for service. If the locomotive is not accepted for service within the 1-year grace period, then the 15-year clocks starts anyway. This greatly incentivizes owners of locomotives such as Mid-Continent to not install tubes unless they feel confident the locomotive will be ready for operation in one year or less.
The next step for C&NW 1385’s boiler is the hydro test. Stay tuned!
With structural welding and the post-weld heat treatment complete, the next step on Chicago & North Western #1385’s boiler progression was sandblasting and painting. This step was recently completed as seen in these photos supplied by Continental Fabricators. Paint has only been applied to the inside of the boiler at this stage. The exterior will be painted a bit later in the process.
C&NW #1385 boiler after being sandblasted. Photo courtesy Continental Fabricators.
Closer view of C&NW #1385 front tube sheet after being sandblasted. Photo courtesy Continental Fabricators.
Peering inside C&NW #1385’s freshly painted interior of the new boiler. This view is looking in from the front of the boiler toward the rear tube sheet and firebox. Photo courtesy Continental Fabricators.
The paint is APEXIOR No. 1, a product that has been used in locomotive boilers going back many decades and is proven effective and typically lasts for decades. The paint is designed to withstand continuous immersion in boiling water and steam up to 698°F (370°C). It serves to aid in preventing corrosion and scale buildup in the boiler by preventing the boiler water from touching the metal of the boiler shell.
Next on the to-do list: rolling boiler tubes.
The busy bees at Continental Fabricators have been making excellent progress on C&NW #1385’s new boiler. By late August work on staybolt installation was wrapping up. The next few photos show that work taking place.
The first shot is looking from inside the firebox at the firedoor ring and we can see the finished welding.
In this second picture we’re looking toward the front of the firebox at the crownsheet and rear tubesheet. The small group of staybolts not yet welded in are the flexible stays and the larger holes in the firebox sheets will accept the arch tubes. The arch tubes have a dual purpose in that they will form a structure to hold the arch brick in the firebox. They will also promote much better water circulation around the firebox while the locomotive is in operation.
This third shot shows the outside of the staybolts yet to be finished and with the boiler rotated on its side. We’re looking at the top of the vessel in the center of the picture.
This fourth picture is looking down through the steam dome inside the boiler at the braces welded in place to support the rear tubesheet. Those braces were discussed in an earlier update and this is a look at the finished product.
With the structural welding completed, as people across the nation were getting ready to fire up their grills for Labor Day weekend cookouts, the folks at Continental Fabricators were preparing a roast of their own. C&NW 1385’s boiler was moved inside Continental’s enormous heat treating oven for its Post Weld Heat Treatment (or PWHT). This process helps to relieve stresses built up during the welding process. The following two photos were taken while the boiler was cooling off after completing the heat treatment.
Next up, the boiler will get sandblasted and painted. The interior will receive Apexior paint which will help protect the steel from corrosion as it boils the water for steam.