1385 Firebox and Wrapper Assembly

Our previous post provided a tour of the Continental Fabricators facility where the brand new boiler C&NW #1385 boiler is being constructed. In this post, 1385 Task Force member Pete Deets shares his photos taken of the 1385 boiler during their shop tour in late February.


At the end of the previous post, I thought I spied something familiar. Could it be our own beloved R-1 in the distance?

Indeed, here are the pieces of the new vessel.


This is actually an assembly table embedded in the shop floor which gives the boilermakers a stable, flat surface to work from. The mudring/firebox assembly is mounted to standoffs on the I beams and is set up to be level and square. With the foundation ring level and square the rest of the boiler assembly can be indexed off that so there won’t be twists and turns where we don’t want them. The boiler barrel courses/smokebox assembly is on the I beams ahead of the firebox. In the photo above Tyler R. of SPEC Machine inspects the wrapper assembly. In the photo below Tyler and Steve R. talk over the boiler with Tom G. of Continental.

From the other side of the assembly table we’re looking into the smokebox at the front tubesheet with the firebox assembly setting beside it. The small holes are 2-inch diameter for the tubes and the larger holes are 5 inches for the superheater flues. The largest hole is for the dry pipe which will carry the steam from the throttle inside the steam dome of the boiler into the superheater header which lives in the smokebox. After traveling through the superheater units the steam will leave the high temperature side of the superheater header and head down the branch pipes to the valves and cylinders to make everything move.

The above picture is looking through the dry pipe hole at the rear tubesheet on the firebox assembly. It won’t be too long before these are joined together.

Here is a good look at the backhead portion of the wrapper assembly. You can see temporary “strongback” braces that are welded on here as on many of the other parts. These are to minimize warping from the heat of the welding process and are used to keep flat sheets flat and round pieces round.

This is a look inside the wrapper assembly at the permanent braces that are attached between the wrapper shell and the backhead. The Continental staff spent several weeks laying out and fitting the braces because there will be staybolts installed in every one of the small holes in the wrapper. The stays will tie the firebox and wrapper sheet together as the steam inside tries to push them apart. There must be a specified clearance or space between the braces and staybolts so they can’t rub.

Here is a closer look at a pair of stays that required a slight bit of adjustment.

This is a look at one corner of the mudring/firebox. The tab at the left of the photo is tacked in place to help locate the wrapper as it is lowered onto the mudring. The U-shaped pieces of wire will be used as spacers between the wrapper and mudring to maintain the required gap between them as part of the full penetration welding process. The written welding procedure states a specified gap must be maintained between the parts and that gap is filled with the welding rod in what is called the “root pass” of the weld. The wrapper will first be tacked into place with several small welds and the spacers will then be removed to allow the procedure to continue.

Here is a little closer look at the finished full penetration weld joining the firebox to the mudring.

This is the bottom of the wrapper assembly where it will be welded to the mudring. The edge is ground off at an angle or beveled to allow the welder to reach to the very inside edge of where the wrapper and mudring will meet. This is vital to allow the “root pass” to join the innermost surfaces of the wrapper to the mudring and then layers of weld will be built up on top of the root to the full thickness of the wrapper sheet. This way the joint between the pieces can be considered as strong as the pieces that are joined together.

This is looking up at the center rear of the top of the inside of the firebox. The 2 pieces of the firebox join the door sheet and the weld line runs down the centerline of the boiler. You can also see how the staybolt holes are beveled like the bottom of the wrapper was to allow for the full penetration weld.

Here’s one last shot of Tyler, Steve & Tom.


A few days after the visit, Tom from Continental Fabricator’s sent over a photo he took on March 4th showing further progress on the firebox/wrapper assembly.

Flexible Staybolt Design and a Boiler Factory Tour

Photos and text by Pete Deets

Staybolt Update

No, this is not a fleet of UFO’s lined up at SPEC Machine. These are the caps for the latest batch of flexible staybolts being made for the 1385.

 

The caps and sleeves shown (above) and the staybolt itself is completed when a ball end (below left) is threaded onto the bolt and the bolt is placed into the sleeve (below right).

Below is a comparison of the two types.

You may wonder why we need 2 types of flexi’s. That is because we have to allow for support of curved as well as flat surfaces. This illustration from the 1938 Flannery Staybolt Catalog shows how the first batch of staybolts will be applied. This is the UW style and is designed to be used where the staybolt will be going through the supported sheet at close to a right angle and the inside and outside sheets are very close to parallel. The flexible staybolts on the throat sheet at the front corners of the firebox will utilize the UW style.

The latest batch is the WR style which is designed to be applied where the inside and outside sheets curve at different rates and do not run parallel. This is the situation near the top of the wrapper sheet and firebox. Because the top of the firebox (the crownsheet) is rolled in a tighter radius than the wrapper sheet and the rigid end of the staybolt needs to be square to the sheet it is attached to the flexible end goes through its’ sheet at some angle.

All these parts are coming together and will be forming a boiler very soon.

A Look Inside the Continental Fabricators Factory

I took a quick trip with Steve & Tyler Roudebush of SPEC Machine to deliver a palette of parts to Continental Fabricating in St. Louis as well as inspect the progress on the new boiler for 1385. More photos and details about the boiler will be posted later but I wanted to share a few shots of Continental’s shop. I hope this will give folks a feel for the size of operation building our vessel.

 

1385 Project in BIC Magazine

Continental Fabricators was recently highlighted in Business & Industry Connection magazine. In discussing current projects at Continental, boiler fabrication for US Sugar #148 and Mid-Continent’s own C&NW #1385 were highlighted as the type of specialty projects Continental is capable of tackling.

You can check out the digital edition of the magazine, which includes a photo of 1385’s boiler.

BIC Magazine’s circulation includes industry managers and executives  in the  refining/petrochemical, drilling, pipeline, marine, terminal, pulp and paper, power generation and heavy construction industries.

Preparing for Backhead Stay Installation

During the last week of January Continental Fabricators began installation of the 1385’s backhead diagonal braces. The backhead is the end of the boiler located within the cab and is a large, flat plate or sheet of steel that has been flanged and then welded to the wrapper sheet.  Flanging is the process of very carefully curling the edges of a sheet to meet the next piece it will be mated to.  The flanging process has been covered in previous update posts.

Much of the boiler is round, a naturally strong shape.  With areas that are flat or nearly flat the forces of nature (including steam pressure) are constantly trying to force them round and thus they require support or “staying”. Staybolts, or “stays” and braces are thus used to reinforce the area and prevent the backhead as well as the other flat areas from bowing outward when the boiler is under pressure.

firebox diagram

While installing these braces, crews at Continental Fabricators flipped the wrapper sheet/backhead assembly upside-down to facilitate easier working conditions. The first photo below shows the assembly as of the last week of January 2019 as the braces are being fitted and tack welded in place.  The tack welds are just enough to hold the braces in place so this assembly can be righted and lowered onto the firebox/mud ring assembly to check for proper clearance between the braces and the firebox.  Once Continental is satisfied with the fit-up between the pieces the wrapper assembly will once again be pulled off the firebox, inverted and the braces will receive the final welds.

upside-down wrapper sheet and backhead

Much of the backhead will be supported via staybolts connected between it and the firebox door sheet. The pictured diagonal braces are used to support the part of the backhead that does not line up with the door sheet and is instead connected to the wrapper sheet for support. This picture was taken during the last week of Jan. 2019. Photo courtesy Continental Fabricators.

A few days later during this the first full week of February, Continental’s crews had flipped the backhead/wrapper sheet assembly right-side-up again and placed it over top the firebox/mud ring assembly. The purpose of doing this is to test fit for any contact between the backhead braces and the firebox crown sheet before final welding of the braces and before the wrapper sheet/backhead assembly is welded to the firebox/mud ring assembly.  Once the two assemblies become one the installation of the staybolts can begin.

1385’s Boiler Assembly Continues

The following is an update on C&NW #1385’s new boiler progress comes courtesy of Continental Fabricators. Continental is the company creating the new boiler for the 1385.

The wrapper sheet has been removed and welding is complete except for the wash out plugs.

The wrapper sheet was fit to ensure all of the firebox stay locations lined up correctly then removed so that we could drill the firebox, as you can see the doorsheet is all that needs to be drilled.  After this is complete the wrapper will be fit and welded for the last time and the entire boiler assembly will be welded together, followed by stay installation.

This photo shows the test fit of 1385’s wrapper sheet and progress with drilling. Photo courtesy Continental Fabricators

When the boiler is completed it will be delivered to Wisconsin where the locomotive will be assembled at the shop of SPEC Machine.