730 Old Boiler Dissection

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NP317
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Re: 730 Old Boiler Dissection

Post by NP317 »

The unseen condition of the crown sheet is good enough proof that :
"When in doubt, change it out."
RN
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Re: 730 Old Boiler Dissection

Post by ccvstmr »

NP317 wrote: Sun Sep 22, 2019 10:03 pm The unseen condition of the crown sheet is good enough proof that :
"When in doubt, change it out."
RN
Well Russ...as you can imagine, changing out a firebox is not as easy as it sounds. More like...raise the safety valves and change out the boiler. While "changing out" is not practical, was hoping this thread would eventually lead to improved boiler care methods to avoid changing out any part of the firebox or a complete boiler replacement. Don't know how many times I've told persons...prevention is a better course than reaction!

Still have more photos to post and then look forward to observations, suggestions, etc. Carl B.
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Fender
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Re: 730 Old Boiler Dissection

Post by Fender »

The thickness of the crown sheet may be unseen, but is not difficult to monitor. An ultrasonic thickness tester is not expensive, and can be used to identify problems that are not revealed by a hydrotest. (This would be done in addition to, not instead of, other inspections.)
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Dan Watson
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Re: 730 Old Boiler Dissection

Post by ccvstmr »

Sentimental Sediment

Sorry for the lag in entries. Still dealing with a medical matter which makes sitting still to compose thoughts difficult at times.

Chaski readers have made several observations based on the photos provided. That's they kind of feedback (and questions) was hoping this thread would generate. For now, would like to offer more documentation before discussions get hot 'n heavy.

With the boiler spread open, several other conditions came to light. Want to go back and touch on a comment made about steel degradation being worse on the "fire side" vs the "water side". Without saying which might have been worse than the other, want to post the next photo again. In particular, take a look at the openings in the girder stay.

IMG_1579.JPG

There appears to be delamination of the crown sheet on the underside, but there was plenty of steel residue on the top side as well. I don't recall ever removing layers of steel from the firebox. With the burners, manifold and secondary air combustion baffles in place, would have been easy to catch and peeling steel. However, will add...with the arch, any such peelings would have fallen down on top and in front of the arch sheet...possibly blocking the lower flues.

Next photo shows the front of the boiler. At this point, will disregard the lack of weld penetration of the front flue sheet to the boiler barrel. Instead, note of the "clump" of residue that formed immediately behind the front flue sheet. If there was ever an indication of low water flow (not low water level)...this would be the reason and location for a front flue sheet wash out plug. This "corner" as with other "corners" around the firebox are not exposed to the somewhat violent cyclonic water flow in the boiler during operation. As a result, sediment in the water settles out and collects without any other form of natural agitation.

IMG_1575.JPG

One of my primary concerns from early on, was the state of the firebox stay bolts. The "better" half of the boiler was set aside for a future club display. The other boiler half was cut into several pieces. Cuts were made behind the front flue sheet and in front of the rear flue sheet. This would expose the boiler barrel and allow surface cleaning tests. And then...a cross cut was made thru the fire box. What you see next are the 2 parts of the firebox from the same side sitting side-by-side...

IMG_1783.JPG

YIKES! NOT GOOD!!! First item evident was the side water legs were loaded...but still porous. While not good for the boiler, was thinking the smaller spaces would decrease the time to heat water to a boil. Would later find...most of the water leg material was magnetic. This (to me) indicated this was steel from the firebox. Won't say any more about the mud ring weld penetration that hasn't already been noted.

IMG_1784.JPG

Next item was the thinning of the firebox/crown sheet upper corners. It appeared the firebox wrapper was formed from a single piece of steel. Could the thinning be a result of corner bending stresses? ...or opening the steel "grain" on the outside allowing faster degradation? Whatever the reason, if the material came off the outside of the firebox wrapper...that came to rest in the water legs.

IMG_1786.JPG

The last item was...the stay bolts seemed to be intact, but covered with residue (refer above photos). At some point, will attempt to scrape the residue off one or two stay bolts to expose the stay bolt underneath.

Will now offer a view of the front throat sheet mud ring...

IMG_1576.JPG

What you see is exactly the condition seen when the boiler was split open. This section of mud ring was clear and with good reason. With the blow down valves open on both sides of the firebox, I could look thru the void and run a 3/32" or 1/8" rod thru the opening to agitate any material that had collected and hopefully flush that out as the boiler was filled for firing. If there was ever a need for mud ring cleaning/wash out ports...at all corners of the mud ring (or as many corners as possible)...this would be it.

Believe I commented in the write up on the Rutland new boiler, that blow down valves provide a false sense of cleaning the ENTIRE mudring. Water (under pressure) like electricity follow the path of least resistance. My opinion...as soon as there's a path established for water to escape via a blow down valve...sediment in the rest of the mud ring will set there undisturbed. Hence the need for occasional cleaning.

Needless to say, was a GREATLY disheartened about the condition of the Rutland old boiler water legs. Recalled seeing a couple fireboxes at Ridge Loco Works that were packed even worse than the Rutland old boiler. Believe Marty Knox posted one such photo on Chaski. In one of those cases, the firebox was bulged.

There's an old joke about how to get to Carnegie Hall? Practice, practice, practice. As such, what's the best way to care for a boiler? Clean, clean, clean. Question is...how often should cleaning be performed? ...1x per year? ...more often? This will be one of those discussion/debate topics where most everyone will have an idea how to address this.

Still have a few more photos and thoughts to share. I shall return. Carl B.
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NP317
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Re: 730 Old Boiler Dissection

Post by NP317 »

CarlB:
"Change it out."
I was referring to replacing the entire boiler.
When a crown sheet is that eroded, the rest of the pressure vessel becomes suspect.
Just my approach.
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Re: 730 Old Boiler Dissection

Post by Steggy »

ccvstmr wrote: Fri Sep 27, 2019 9:59 amThere's an old joke about how to get to Carnegie Hall? Practice, practice, practice. As such, what's the best way to care for a boiler? Clean, clean, clean. Question is...how often should cleaning be performed? ...1x per year? ...more often? This will be one of those discussion/debate topics where most everyone will have an idea how to address this.
Also to be contemplated is the wisdom of using chemically-active cleaning agents. They have the potential to break loose gunk, which presumably can be expelled through the washout ports. However, the next question is what are the chemically-active agents doing to the interior of the boiler.

Back when I was working at a certain railroad supply manufacturer, we would advise the users of steam generators in hard water areas to occasionally run a solution of sulfamic acid (H3NSO3) and water through the coils. This procedure was generally quite effective in removing scale, and would not damage the coils, which were wound from DOM steel tube. However, it was necessary to disconnect the feedwater pump and check valve from the coil inlet to avoid seal damage, as well as damage to the aluminum body of the pump.

In at least one case (a railroad who will remain unnamed due to having a maintenance crew at the time that was trained by the Three Stooges—Carl will know of which railroad I speak :D ), a mixture of hydrochloric acid—the active chemical in commercial-grade toilet bowl cleaner—and water was used. It removed the scale alright—along with a significant quantity of "rust" (technically, iron(III) oxide), which of course, was material from the inside of the coil tubing. Thanks to that little stunt, yours truly ended up supervising the replacement of the coils, not a trivial process on a steam generator crammed into the rear of an E-unit. :shock:
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Re: 730 Old Boiler Dissection

Post by doublereefed »

I still don't understand what process thinned out that crown sheet relative to the rest of the sheets. Am I to understand that a new one was welded in at some point?
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Re: 730 Old Boiler Dissection

Post by ccvstmr »

NP317 wrote: Fri Sep 27, 2019 10:39 am CarlB:
"Change it out."
I was referring to replacing the entire boiler.
When a crown sheet is that eroded, the rest of the pressure vessel becomes suspect.
Just my approach.
RN
Hi Russ...well, believe this was pointed out in the 703 New Boiler thread.

One of the options provided was to cut out the old firebox, flues and front flue sheet. No cost estimated would be provided other than "time and material". Maybe that would have been less expensive...maybe not. At that point, there was no way of knowing the condition of the boiler barrel. In particular, the bottom surface (6 o'clock position) where water might reside after a day of operation and blow down. Saw little value to replace other parts of the boiler...only to find 2-5 years down the road the barrel SHOULD have been replaced from the start.

Decided to bite the bullet and simply get an entire new boiler. I knew the entire process would not be cheap, but at that point, I simply wanted to get back on the rails and get steaming once again. There were a couple benefits to the new boiler solution...upgraded boiler design with a keyhole firebox vs rectangular firebox. This increased the number of flues...ie, more heat exchange area. Another benefit included slightly wider water legs that might be easier to clean (or another way of looking at...take longer to fill with sediment).

During the new boiler discussions, the subject came up regarding a tapered boiler. The original 730 boiler had a straight boiler and a dummy tapered boiler jacket decoration. Asked Ridge Loco Works if there was any value in building a true tapered boiler? Considering the slight benefit of marginally increasing the steam space vs the added cost...decided to stick with the straight boiler design and used the dummy tapered boiler jacket with added/improved insulation wrapped around the back half of the boiler.

In the end, like to think the better decision was made. Carl B.
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Re: 730 Old Boiler Dissection

Post by ccvstmr »

Fender wrote: Fri Sep 27, 2019 9:49 am The thickness of the crown sheet may be unseen, but is not difficult to monitor. An ultrasonic thickness tester is not expensive, and can be used to identify problems that are not revealed by a hydrotest. (This would be done in addition to, not instead of, other inspections.)
Hello Dan...evidently there are a lot of those ultrasonic testing units "out there". Looks like they're made by one company and private labeled for others. Many look the same. Saw some prices down around $20! Also saw where the calibration gauges cost MORE than the test unit itself!

There's one problem that comes up when identifying such a tool. What are the condemning limits? If I recall, those units can measure material thickness down to 1.2mm or .047". Also wonder how clean the surface has to be to get accurate readings?

The next time I'm at the shop where the old boiler is (during the next week or two), I'll put a caliper/micrometer to the boiler barrel, crown sheet and other surfaces to measure thickness. Will gladly share those values with the Chaski gang as part of this thread. There's nothing to hide here.

Would seem most of us operate under the "it's okay until it doesn't work" philosophy. Not saying that's good or bad...more like, fact of life. Not much different that automobiles, appliances and other devices. Comes down to...cost to repair vs cost to replace. However, at such a low price, it might be worth the investment. It's not much worse than getting a pair of channelok pliers. Thanks for the heads up on the tester. Carl B.
Life is like a sewer...what you get out of it depends on what you put into it!
I don't walk on water...I just learned where some of the stepping stones are!
I love mankind...it's some of the people I can't stand!
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Re: 730 Old Boiler Dissection

Post by ccvstmr »

doublereefed wrote: Sat Sep 28, 2019 12:16 pm I still don't understand what process thinned out that crown sheet relative to the rest of the sheets. Am I to understand that a new one was welded in at some point?
Hello doublereefed...

The "thinning process"? Would attribute that to rust formation during periods of non-use (poor dry-out practices, other) and the crown sheet being one of the most thermally exposed surface of the firebox during operation.

Back in 2005, a new front flue sheet was installed and welded in place as part of an effort to replace the original steel flues. Those flues were welded in the fire box and rolled in place in the front flue sheet. No other fire box surfaces were replaced. Thereafter, all the flues were replaced with hard copper pipe and silver soldered in place at both ends.

Carl B.
Life is like a sewer...what you get out of it depends on what you put into it!
I don't walk on water...I just learned where some of the stepping stones are!
I love mankind...it's some of the people I can't stand!
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Re: 730 Old Boiler Dissection

Post by Marty_Knox »

BigDumbDinosaur wrote: Fri Sep 27, 2019 2:44 pm Back when I was working at a certain railroad supply manufacturer, we would advise the users of steam generators in hard water areas to occasionally run a solution of sulfamic acid (H3NSO3) and water through the coils. This procedure was generally quite effective in removing scale, and would not damage the coils, which were wound from DOM steel tube.
BDD, I was very interested to read this. The first department I worked in when I hired in as a boilermaker at DuPont's Grasselli Plant was the Sulfamic Acid Dept. Making Sulfamic Acid is an exothermic process. When you mix urea and oleum it gives off a tremendous amount of heat. We had steam cooling coils in the mixing vats. Yes, I said steam cooled!
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Fender
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Re: 730 Old Boiler Dissection

Post by Fender »

Carl,
The tester I bought came with “testing standard”, which is a coin-shaped piece of steel of known thickness (I believe it is 4 mm). In operation, you adjust the device so that it registers 4 mm on the display when using the tester on the standard. The way the tester works is that it measures the time the ultrasonic pulse takes to go through the sample and be reflected back from the other side. To get a clear reading, the tested surface must be clean and relatively flat. I used some glycerin between the boiler and the transducer so a clear signal is received. I used some sandpaper to clean off oxidation and soot from the inside of the firebox.
There are several things that will prevent a clear reading. If the surface is rough or pitted (on either side), or if the surface is not sufficiently flat, such as in a sharp corner.
Since sound propagates at different speeds in different materials, the device would need to be recalibrated for copper or other boiler materials.
Generally, scale or rust buildup on the water side will not prevent a good reading, because the ultrasound signal will reflect from the interface between the steel and the dissimilar rust or scale, not from the outside surface of the rust/scale.
Again, I consider this as an additional test method, not as a substitute for hydrotesting or othe boiler inspection (looking for leaks, bulges, etc.)
Dan Watson
Chattanooga, TN
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