We are in the mist of doing our boiler inspection. We have removed the boiler belly braces to inspect the boiler shell and make thickness measurements. We have noticed some wear on the boiler shell where the belly braces were installed. So the question is do you put anything in between the boiler shell and the belly brace. We have been discussing putting a thin sheet of Teflon in between the boiler shell and the belly brace. Has anybody had any experience doing something similar?

Jack Young CTRC

I assume you are talking about the throat braces that attach in tension to the throat/flue sheet and are attached by rivets in shear to the barrel of the boiler.

I have never heard of putting shims between the brace foot and the shell, and don't have any information to recommend it. Any compressible material, such as teflon, would be counter productive to the riveted attachment.

If the thickness of the shell under the brace feet is sufficient for the operating pressure, I would reattach the braces with no further work to the shell. If the shell is too thin or nearly too thin, determine the shell material, consult the applicable code(s), check with the jurisdiction, and if all is in order use weld buildup (using proper procedures, material, and qualified personnel) to restore the thickness of the shell.

Dunno, Linn, sounds to me like he is talking about the waist braces that are bolted to studs on the belly and connect with a piece of plate to the frame. Some had swing links, some sliders of some sort, but just plate seems to be the most common. GM 209 was built with a doubler at the point at which the waist braces are fit to the boiler, but many engines were not, and it makes a fine place for water to hide and pit while stored cold.

A thin sheet of something not hydroscopic would probably be your best bet if you do want to put in a liner. The plate simply flexes to absorb the expansion cycle as the boiler breathes in service, so you do want to get it pretty well tightly reattatched.

Unlelss you were talking about the internal braces, in which case ignore this.

dave

If it is the waist sheet, my comments definitely do not apply.

Waist sheets are a bit of a mystery to me, particularly as to what supports what. Some are fastened to the boiler while others slide on the boiler shell. Some don't touch, but show signs of wear - as if it is there to keep the frame from humping up to much. It has been my impression that the boiler is stiffer than the frame on most engines I have worked on.

The question is in regard to the waste angle supports beneath each course. At one time on this locomotive the supports were fastened to the boiler with studs. Later the studs were removed and the boiler floated on the waste angle. Some time during service the waste angle did come in contact with the number two course. Wear is visible. Measurements have been taken and repairs are necessary.

Might want to think about replacing the studs so you can stabilize the joint to prevent future wear from the parts moving against each other. The movement within the brace is more than adequately covered by flexing of the brace plate.

dave

Depending upon the length/height of the waist sheet, you may or may not want to replace the studs. If it is a short sheet it will put more stress on the studs as the sheet flexes, putting more stress on the studs and causing them to come loose or break and possible causing sheet damage.

Without seeing the wastage, it seems to me that this could be repaired with weld buildup, again subject to jurisdictional requirements. Once restored, a shim could be added by welding it to the barrel using fillet welds. The shim must be code material. Another option is to use extra weld buildup to act as a wear shim. Both cases may be considered an alteration as they alter the contour of the vessel 2001 NBIC, App. 6, C. 4. This could also be a repair under 2001 NBIC, App. 6, B. 2. d.; or B. 3.; Again that would be a jurisdictional issue.

Since it may be difficult to predict the stresses caused by re-attaching the sheet, and the fact that the studs were removed for some reason, it may be best to continue to allow the sheet to float. I don't know that a teflon shim would gain anything material.

I appricate this discussion. About two years ago a guy told me according to the "books", about 1920 or so the "normal" practice was not to reattach the angle, but to allow to float. Ever since then I look to see how or if the waste sheet angle is attached or not. Mostly I have seem them attached. The only one I can think of that wasn't was the two narrow guage engines up at the Quincy mine musuem. It looked like the inhouse repair from hell. Actually all the repairs looked that way by todays standards. If memory serves me right, they welded {loose terms} a shim on the boiler course where obvious contact had been taking place. I love looking at these two engines and the repairs that they received. Scary.

Question: is the contact coming from the boiler not being secured to the waste sheet or from the expansion and contraction? Not sure how to word this question. I know the waste sheet isn't supposed to be really supporting any thing, but does it? My understanding which is limited, is that the waste sheets support the frame from binding? I guess I am wondering if the boiler is secured {even if only by the waste sheet}in two places, {saddle and waste sheet} if it might NOT flex as much and make destuctive contact. Being that I can't seem to find a right or wrong answer by my own observations, maybe some one has some insight. I feel this is a great subject now that so many boilers are removed from frames and this area come under inspection and repair. I hope you can understand my questions. Thanks.

Cheers, John

Linn is correct about a short waist brace plate - i am in the middle of a decapod right now so had that in my mind, and I don't know your engine so my suggestion to definitely replace the studs might not be the best bet if the height is short and the width wide. If not, new studs might be a good idea.

Adding a shim to the boiler, whether by build up or by an additional layer of boilerplate, will provide a protection against future wear going deep enough to require more repair, which is caused by the surfaces rubbing against each other as the locomotive flexes and breathes. Not attatching to the boiler, but interposing a layer of teflon or nylatron attatched to the top of the waist brace after repairing the boiler would also protect against wear, for a while. Check out temperature characteristics. The attatchment with studs protects against wear by preventing the parts from rubbing by connecting them rigidly, assuming stresses are not so great as to shear the studs or damage their attatchments as Linn says.

Brings me to another point: were the studs removed for a reason on purpose, or did they just break off and never were replaced? If the area is pitted as well as worn, and the stud stumps are still in the boiler and not removed and plug welded, they may have been weakened by external corrosion and broken when torqued with a wrench rather than fractured by failure in mechanical stress under steam - look at what remains. I generally trust the original designers better than myself and default to that unless presented with good evidence otherwise.

The mechanical forensic parts of the job are fascinating, we need more of this sort of discussion.

dave

The boiler moves longitudinally due to expansion and contraction as the boiler is warmed or cooled. This movement is relatively slow and the amount of movement decreases the closer you get to the cylinder saddle which should be the only rigid connection between the frame and the boiler. Wear from this movement would probably be minimal.

As I stated earlier, most of the frames I have seen are considerably less rigid than the boiler. My guess is that when the frame receives forces that cause it to flex upward or sideways in the area of the waist sheet, these forces are transmitted to the boiler. If the sheet floats there could be a certain amount of abrasion taking place which will not occur if the sheet is attached to the shell.

If the attachment to the shell is rigid, it is most likely stress free when the engine is cold and will be in a stressed condition when the boiler is hot. The amount of stress depends upon the location and size of the waist sheet. The shorter and closer to the rear of the boiler, the greater the stress. This stress is transfered to some degree to the shell itself. I suspect that when these were changed to floaters it was to eliminate this stress. Without somewhat exhaustive studies, the determination of these stresses is not possible. It may end up being a coin toss.

I would say that once restored, the shell will probably last a very long time with a floating sheet, given the probable service of the locomotive.

Thanks Linn for your explanation. I have wondered about this attachment for a while and not having much luck figuring out if it was a good idea or not. Both ways have there logical points. I would suppose if the brace {forgive me I don't know the name of it and it will take me all night to find it} that supports the firebox to the frame would wear down after a hundred years causing a very slight missalignment that would cause some wear to these friction points as well?

Linn or anybody else if you read this could you answer one more question? What then causes the saddle to work? When I was working with the "good ole boys" from Midwest Locomotive and Machine preparing the Copper Range #29 to be moved, we noticed that it had been working the saddle.. Wasn't real bad, but it was showing. I realize this isn't probably related to the waste sheet questions, but it does make me wonder about frame/boiler stresses and where the stresses transfer too.

Thanks again for you insights. John.

Frames working on the saddle, the boiler working in the saddle, or the saddle halves (assuming that design) working against each other? I just inspected a locomotive exhibiting an unsafe amount of all 3.

dave

One more question regarding braces (and shoes for that matter). On boilers with a bolted rear waist sheet (under the rear of the firebox) how much preload, if any, is placed on the sliding boiler shoes and sliding type boiler braces when the boiler is cold? I am thinking that with the frame being straight (under no strain), the boiler should just rest on the brace saddles and the boiler shoes. We do have to keep in mind the boiler expands in ALL directions when fired up. Not only in length but in circumference as well. Most boiler expansion takes place to the rear but there is some upward and outward growth. One thing to add to this problem is that the rear waist sheet is canted towards the front of the engine about 7 degrees. As the locomotive grows toward the rear, the rear of the boiler is lifted slightly as the rear waist sheet is pushed towards vertical.

Dave I think it was frame against saddle. Though the smoke box was rotten as they come? I would have to ask Steve or TJ to be sure. They had poured Concrete in the bottom of the smoke box to try and seal it up. Steve had the pleasure of chipping it out so he could burn the saddle bolts out. The impression I had was it was frame against saddle. Thanks, John.

I am always interested in how Linn and I approach situations from different oblique angles - who's to say if I had his education and experience I wouldn't share his POV? In any case it is provocative to thought at the very least, and I wish some guys like Rimmasch and Butler would chime in a little more for other ideas.

I looked up what was in the Baldwin, Lima and Alco S&P books - only Baldwin provided a spec for waist sheet application that I could find, which in 1943 essentially was:
1. rivet reinforcing plate to boiler
2. weld (angle or T) to reinforcing plate
3. bolt waist sheet to (angle or T)
So, they are in favor of rigid attatchment with the additional reinforcement provided first - pretty much what I was looking at on the decapod, which was built in 1930, so this is what they were doing for at least 13 years.

Where this leaves the locomotive under discussion I have no idea. Not much help from here John, sorry, unless you are doing a 1943 Baldwin.

OK, on to loose frames. Short story is they just get that way after a lot of repetitious stresses. Attatchment is tapered bolts into tapered reamed holes (usually 1/16 to the foot) which are driven in, and interfaces between frame and saddle keyed. As the locomotive bounces it way down the track, absorbing reciprocating and rotating weight stresses, the joints are pushed, pulled, and twisted constantly. After a while a tiny bit of give develops. This leads to an ever increasing greater looseness as every hole gets bigger and every surface starts to bash itself against whatever it is supposed to be up against. If left without rereaming and application of larger tapered bolts and keys to achieve new tightness, the holes start to spall, the frame walls around the holes start to crack, and pretty soon you have more pieces of frame than you wanted.

Look for clues such as frame keys welded in, big clamps tightened around the assemblies, lines worn onto metal adjacent to connections, snail trails of rusty powder eminating from connections, etc. Of course, for real excitement, ride the pilot beam on rough track and watch them move against each other. Not for the faint of heart.......nor obviously wrong to the clueless. Some scary stuff out there.

I can just hear Steven commenting as he bashed out the concrete.

dave