REPLACING TUBES IN A STEAM BOILER.. Well we got the junk out of the smokebox, and that was the goal for the days work, only it wasn't yet noon, so Stathi said well, were here and we have the time, lets go ahead and start on the tubes.
Replacing tubes was all new to me.. I have seen videos, I have read a lot, and generally got the idea, But there are a lot of little things that I never knew, as I had never been actively involved in the work. So when it was decided that we needed to replace a few tubes, It was decided that the boiler guys at the C&T would do it, as none of the active crew members had ever had hands on experience on 315's tubes. Ten years ago when we un-stuffed her from the park, the shop guys at the D&S were tasked with the re-tubing. I put the word out that when the C&T crew was going to tackle the tubes to let me know, and I would drive over and assist any way I could, so I would have some first hand knowledge of what all was to be done, and I'm writing as best I can a maintenance and repair manual for 315. We had the time, he wanted to do it, and I was eager to learn, so away we go.
The five offending tubes were Identified by Stathi from the firebox end, and I marked them in the smoke box end. Easy to find.. Shine a light thru them.
NOTES about the drawings I made.. Not to scale, and not technically accurate, as I over emphasized some things for scale and to get the point across..
The tubes run thru the boiler from the firebox to the smokebox. Each end of the tube is handled differently in how its sealed to the tube sheet.
Drawing #1 cross section of the tube sheet at the smoke box side. Note the small space sticking past the tube sheet.
Note that the tube only goes thru the tube sheet, it is rolled ( more on that latter) with no welding or other treatment. Simple to do.
Tube ends in the smokebox.
Note that they are just sticking out.
Drawing #2 cross section of the front tube sheet and tube on the firebox side.
Note that the tube on this end has been rolled (more on that latter ) with the protruding end has been rolled over and “Beaded” over onto the tube sheet, and then “Seal Welded” against the tube sheet.
I showed these two drawings so you can have better clarity of the pieces as I explained what we did. I’ll start in the smoke box side, as that is where I spent most of the day.
To “Free” the rolled tube from the tube sheet, all that is done is a cutting torch is precisely used to cut thru the tube lengthwise where it passes thru the front tube sheet in three places. Note that there is no “Beading” or welding on the front end. Its “Cooler” and there is less stress on this end of the boiler, then at the firebox end, less thermal expansion also.
Great care is taken to be sure not to cut into the tube sheet.
After cutting, I used a cold chisel, and bent the cut ends inward to free the tube from the sheet.
Thats all there is to prepping the smokebox end for tube removal. Now actually getting the tube out is yet another challenge. On to the firebox side.
I did not get to take any photos inside the firebox side, Two guys inside there is really tight, and I was working the front as Stathi worked the firebox. Back to the drawings, Referencing back to drawing #1 as a side view, and now a front view.
Drawing #3 straight on view of the front tube sheet and tubes on the firebox side.
#1 - end view showing the beaded over tube with the seal weld all around the tube.
#2 - #3 showed that we had to grind off the seal weld around the tube, leaving the beading in place.
#4 - Shows the three torch cuts radial on the tube end, and carefully avoiding the tube sheet.
#5 - Shows the end of the tube after chiseled into itself, freeing it from the tube sheet.
Drawing #4 shows what the objective is, after cutting, and bending the tube to free it.
The tube is free of the tube sheets. In this case, we only had to do 5 tubes. when you have to do a FRA mandated 1472 inspection, and re-tube the boiler, you have to do ALL THE TUBES. Very time consuming. 315 has only 152 tubes, not that many, and they are all the same size, really big locos can have hundreds more then we have. Also no superheater and oversize tubes.
For this job, we were able to push/pull the tubes out thru the firebox.
To get them out, we used a 10 foot rod, and I held it on the end of the bent over tube in the fire box, and Scott Gibbs wackked the other end of the rod with a sledge hammer, and we drove all twelve feet out, one wack at a time. Several of the tubes just slid out, one we wackked and wackked for about three feet, then we rigged a come-a-long on the firebox end and pulled it on out. A lot of work!
Before we can put the new tube in we have to clean up the holes in the tube sheet.
An air die grinder with a sanding flap disc, does the job. You need to clean the hole in the sheet, and de-burr the inside and the outside edges, Care must be taken not to over do the grinding and make the hole any larger then absolutely necessary.
All set for new tubes,,
This was done on both ends of the boiler.
UP NEXT: Installing the new tubes..