The Insides of a Steam Locomotive

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Mark D
Conductor
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Joined: Fri Jul 15, 2005 5:01 pm
Location: Sort of between Litchfield and Forest City, MN.

The Insides of a Steam Locomotive

Postby Mark D » Sun Apr 14, 2019 1:49 pm

You all have seen a steam locomotive somewhere and some time back in your lives I'm sure. But not many get to squeeze can get the 'opportunity' to explore the insides of one. I had the bad luck to have to do just that.
Most of you know I'm part of the crew of the former Milwaukee Road S-3 Northern type steam locomotive that we do operate.
Well, it's time to replace the circulator tubes. Using ultra sound testing we've determined that it's time to have new tubes made to replace the originals. They lived a long life, new in 1944. The nominal wall thickness of the tubes is .375". (3/8") We were getting areas that would be good at .360, give or take, But too many places were down to numbers such as .245 and such. That's not good. Time to replace them.
So that's why I was in there. To take measurements.
Since we are going to be cutting out the old circulator tubes, we need to take measurements between each horizontal tube. The reason is that while you don't see in the photo any large curved bricks is because they've all been removed for the testing and ultimately replacement of the tubes.
Those arch bricks, as they're called, just sit on the circulator tubes using mortar to seal between the bricks, just as you would on a brick building. If the circulators aren't in the right spot the arch bricks won't fit, either too high, not settled in, or drop right through. Either way isn't good.
The next step is to cut out the first (front) tubes out and replace them with brand new that probably won't fit perfectly, so that will require some special and very delicate work using torch, maul, pry bars, grinding, welding and more. Sort of similar to repairing a Swiss watch.
As the new piping goes in, it has to be within 1/8" of the original spec's. Seems easy to me, but it's really not. As that stuff is welded, the heat will cause it to move on its own as the welding goes on.

Here's what the left side looks, the other side is a mirror image. I asked a guy who was working in there, helping me get the needed numbers, to take a photo of the inside because I didn't have a camera with me. He used his cell phone and emailed it to me. Problem is, it was so huge it took an hour to get it down to fit here. In the end, it wound up to be a bit too small. Oh well.
That butt happens to be me leaving the firebox through the fire door that's just big enough to snake through. I was trying to get out of there before he got me in the photo. I was done taking the measurements.
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FIREBOX 261 LEFT SIDE FACING AFT (resized).jpg
FIREBOX 261 LEFT SIDE FACING AFT (resized).jpg (40.22 KiB) Viewed 599 times
Mark D. - The bottom of the information curve

John Bohon
Conductor
Posts: 400
Joined: Sat Jul 23, 2005 9:30 pm
Location: North Carolina

Re: The Insides of a Steam Locomotive

Postby John Bohon » Sun Apr 14, 2019 3:09 pm

Having spent an uncounted number of days inside boilers and fireboxes over the last 40 years I feel your pain. The work is dirty, hard, and generally miserable. It can be very boring as well as well as difficult. It is seldom pleasant. I feel for the guys doing the work. On the other hand I have never worked on a firebox with this style of circulator tubes. Please post photos and information about the replacement as you go. You have an interesting project in a very confined area. The good news is once you are finished the new circulators should last a very long time.

John Bohon

Mark D
Conductor
Posts: 3298
Joined: Fri Jul 15, 2005 5:01 pm
Location: Sort of between Litchfield and Forest City, MN.

Re: The Insides of a Steam Locomotive

Postby Mark D » Sun Apr 14, 2019 8:40 pm

They will probably far out live the operating time that engine will ever see.
Yeah, most circulators come into the firebox low down on the side sheets and then turn upward to the roof. At least, that's the only other picture I've ever seen of circulators. But what we have seems to work just fine. It's just that it's getting a bit thin and nobody wants to have something blow open while hauling a train with a bunch of formerly (if it were to happen) happy riders.

Mark D.
Mark D. - The bottom of the information curve


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