730 Old Boiler Dissection

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Fender
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Re: 730 Old Boiler Dissection

Post by Fender »

As far as condemning limits, I seem to remember that a loss of 40% of the original thickness indicates that replacement is warranted. I suppose you’d need to consider the original factor of safety too. Maybe Marty can correct me on this?
Dan Watson
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10 Wheeler Rob
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Re: 730 Old Boiler Dissection

Post by 10 Wheeler Rob »

I suspect the horizontal crown sheet corroded quicker than the vertical side walls because the of 3 factors. First the crown sheet is more prone to scale build up staying in place, second the fire is directed towards it, and third the side walls have better heat removal buy the convection of the boiling water. These factors mean its going to be hotter than the side walls which accelerates the corrosion.

So this makes me conclude maybe the crown sheet should be made thicker for better boiler life. It also makes me think some clean out ports allowing crown sheet cleaning could be benifical.

Anyway keeping scale build up down through water chemistry and periodic cleaning is probably the best defense, but difficult for us for us weekend engineers that do not spend much time on internal boiler mantainence.

Rob

Rob
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Re: 730 Old Boiler Dissection

Post by rkcarguy »

I think with what I've seen here and in other posts with the "legs" being chock full of scale, I'd prefer to leave the lower sides of the firebox "dry" and line the sides and back of the firebox with 1/2 thickness fire brick/insulation instead. Could the horizontal crown sheet be tilted forward somewhat to aid water circulation and prevent build up from sitting on top of it? Also, I'd think some sacrificial zinc anodes would greatly reduce the corrosion. Any time you have something steel and you add brass fittings and water, you've just created a battery that is going to consume the steel somewhere unless you give it something else to "eat".
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Re: 730 Old Boiler Dissection

Post by Glenn Brooks »

Very interesting discussion. Ryan’s idea about using sacrificial zincs is intriguing.

One thing that struck me about this boiler design is that the builder looks to have built the crown sheet flat on top, with very sharp radius corners. My two boilers, a code boiler in 1950, the other, a riveted boiler from early 1900’s both have round crown sheets - no flat top surfaces, and very smooth, large radii edges - almost circular in design. Certainly elipitcal. They both are in excellent condition, current ultrasound shows almost no reduction in sheet thickness. The picture is the 1900’s boiler.

I am wondering if the flat crown sheet contributed to this boilers early demise. Also wondering if the steel formulation was not appropriate for boiler construction...

Glenn
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Fender
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Re: 730 Old Boiler Dissection

Post by Fender »

Glenn Brooks wrote: Mon Sep 30, 2019 2:54 pm One thing that struck me about this boiler design is that the builder looks to have built the crown sheet flat on top, with very sharp radius corners. My two boilers, a code boiler in 1950, the other, a riveted boiler from early 1900’s both have round crown sheets - no flat top surfaces, and very smooth, large radii edges - almost circular in design. Certainly elipitcal. They both are in excellent condition, current ultrasound shows almost no reduction in sheet thickness. The picture is the 1900’s boiler.

I am wondering if the flat crown sheet contributed to this boilers early demise. Also wondering if the steel formulation was not appropriate for boiler construction...

Glenn
Some very interesting points. At this point, the type of steel used is probably unknown. Was pressure vessel quality steel (such as SA516) used, or something else? Did the radius of the curves and type of steel used contribute to the deterioration in the corners? What boiler water treatments were done, and were they effective?
From the quantity of scale or rust in the firebox sides, my guess is that ineffective or little water treatment and cleaning of the boiler is the biggest factor in the thinning of the sheets.
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rkcarguy
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Re: 730 Old Boiler Dissection

Post by rkcarguy »

Glenn Brooks wrote: Mon Sep 30, 2019 2:54 pm Very interesting discussion. Ryan’s idea about using sacrificial zincs is intriguing.

One thing that struck me about this boiler design is that the builder looks to have built the crown sheet flat on top, with very sharp radius corners. My two boilers, a code boiler in 1950, the other, a riveted boiler from early 1900’s both have round crown sheets - no flat top surfaces, and very smooth, large radii edges - almost circular in design. Certainly elipitcal. They both are in excellent condition, current ultrasound shows almost no reduction in sheet thickness. The picture is the 1900’s boiler.

I am wondering if the flat crown sheet contributed to this boilers early demise. Also wondering if the steel formulation was not appropriate for boiler construction...

Glenn
I just realized something, so this boiler (the cut apart one) was originally steel tubes and they were replaced with copper.
Copper and Steel are a fair distance apart on the galvanic reaction chart, i.e. the steel will be consumed as the "anode" in the "battery". Heat speeds the process, and the crown sheets close proximity to the copper tubes (and all the brass fittings and valves at the control end) and increased heat would have made those copper and brass items the perfect cathodes to eat away the steel. Furthermore, the firebox side tube sheet would have experienced vertical water flow as the water was heated, which probably swirled at the top depositing additional "stuff" on that shelf of a crown sheet.
If you really want to get into this galvanic corrosion science, a good dissimilar metals chart and a digital voltmeter can really go a long ways. In the boating world, voltages created by dissimilar metals on outdrives due to lack of zincs or poor contact/grounding of the zincs to the other parts not only eat your submerged metal parts but higher voltages also spook fish. If you can measure voltage across the two dissimilar metals, then you have some battery action going on which will consume the anodic metal. I know at one point I had 5.8 volts measured across my outdrive castings and my zinc. It turned out that the bolted connection under the zinc wasn't conducting good and the zinc was being eaten quickly. Cleaning everything up and putting a little grease on there to keep the salt water out, dropped it down to less than 1 volt. Any dissimilar metals, say a large brass fitting with Teflon sealing tape around the threads, will act as a cathode and create the battery affect. That's why it's important to use pipe dope or sealant on the brass heads of the zinc anodes so they aren't electrically isolated.
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Re: 730 Old Boiler Dissection

Post by ccvstmr »

Fender wrote: Sat Sep 28, 2019 7:17 pm 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).

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.

Again, I consider this as an additional test method, not as a substitute for hydrotesting or other boiler inspection (looking for leaks, bulges, etc.)
Dan...thanks for the comments on ultrasonic testing. You made several good points. The last comment perhaps being the most important...an ultrasonic test is not a substitute for a hydro test. As noted, these instruments are not expensive. They can be a great little tool. In my case, if it's necessary to lift the boiler off the frame for some non-destructive testing...a casual thickness check is not going to be practical.

Suspect most people in the hobby, might not be interested in knowing their boiler is deteriorating. That decay starts after the 1st steaming of a new boiler. The open question is...how long will the boiler last until it can no longer pass a hydro? The answer depends on too many variables.

Think we can all agree...once metal surfaces start to deteriorate...they do NOT get better. Some sheets are replaceable...others not. In particular, if the surfaces are overly rusted. In which case, the condemning limit becomes... a) when one can no longer generate steam at a rate to overcome leaks that developed... b) when there's water running out of places other than threaded fittings, blow downs, drains or maybe around flues...the end of the line may be in sight. Carl B.
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Re: 730 Old Boiler Dissection

Post by ccvstmr »

10 Wheeler Rob wrote: Sun Sep 29, 2019 5:56 am I suspect the horizontal crown sheet corroded quicker than the vertical side walls because the of 3 factors. First the crown sheet is more prone to scale build up staying in place, second the fire is directed towards it, and third the side walls have better heat removal buy the convection of the boiling water. These factors mean its going to be hotter than the side walls which accelerates the corrosion.

So this makes me conclude maybe the crown sheet should be made thicker for better boiler life. It also makes me think some clean out ports allowing crown sheet cleaning could be beneficial.

Anyway keeping scale build up down through water chemistry and periodic cleaning is probably the best defense, but difficult for us for us weekend engineers that do not spend much time on internal boiler maintenance.

Rob
Rob...there was no doubt the horizontal crown sheet took the brunt of decay. Can't say if crown sheet scale build up was a factor or not. Your other two points carry some validity.

Clean out ports...no doubt, more would be better. Easier to accomplish on larger locos with larger fireboxes.

Water chemistry...here again, good chemistry should help. But believe it all comes down to what goes into the boiler from the start...water quality.

As for the Rutland, the majority of the material in the side/rear water legs...was magnetic. Most likely came from the crown sheet, girder stays and the wet side of the water legs. Would take a little more than "some casual cleaning" to dissolve the steel for removal. Prevention being the better course than reaction...good dry out practices might go a long way here. Carl B.
Life is like a sewer...what you get out of it depends on what you put into it!
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Re: 730 Old Boiler Dissection

Post by ccvstmr »

Glenn Brooks wrote: Mon Sep 30, 2019 2:54 pm Very interesting discussion. Ryan’s idea about using sacrificial zincs is intriguing.

One thing that struck me about this boiler design is that the builder looks to have built the crown sheet flat on top, with very sharp radius corners. My two boilers, a code boiler in 1950, the other, a riveted boiler from early 1900’s both have round crown sheets - no flat top surfaces, and very smooth, large radii edges - almost circular in design. Certainly elipitcal. They both are in excellent condition, current ultrasound shows almost no reduction in sheet thickness. The picture is the 1900’s boiler.

I am wondering if the flat crown sheet contributed to this boilers early demise. Also wondering if the steel formulation was not appropriate for boiler construction...

Glenn
Glenn, came to the same conclusion about crown sheet geometry contributing to the boiler failure long before the old Rutland boiler was cut open. Listed this as a criteria for the new boiler construction by Ridge Loco Works. Marty Knox explained the construction of his keyhole firebox supports this concept. Don't need much pitch in the crown sheet...but anything better than flat would be desirable to shed water when the boiler was idle.
Here again, some pix from Marty showing his firebox construction with a "peaked crown sheet"...

IMG_1442.JPG
IMG_1444.JPG
IMG_1457.JPG

Will add, the Rutland boiler did...and still has a sloped mud ring to drain water towards the blow down valves. Can only hope this will eliminate one of the problems with the original boiler fabrication. 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!
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Re: 730 Old Boiler Dissection

Post by ccvstmr »

rkcarguy wrote: Mon Sep 30, 2019 6:21 pm I just realized something, so this boiler (the cut apart one) was originally steel tubes and they were replaced with copper.
Copper and Steel are a fair distance apart on the galvanic reaction chart, i.e. the steel will be consumed as the "anode" in the "battery". Heat speeds the process, and the crown sheets close proximity to the copper tubes (and all the brass fittings and valves at the control end) and increased heat would have made those copper and brass items the perfect cathodes to eat away the steel. Furthermore, the firebox side tube sheet would have experienced vertical water flow as the water was heated, which probably swirled at the top depositing additional "stuff" on that shelf of a crown sheet.
RK...good points. While I've heard only occasionally of some boiler operators installing sacrificial zinc or magnesium rods in their boiler...would think the hobby as a whole (generally speaking) is going to be in a big hurt!

Most steel boilers are now being build with copper flues. At some point as the boiler is mounted and piped, there's going to be a steel to brass/bronze interface for pipes or other boiler accessories. Does galvanic decay occur at such a rate steamers need to be overly concerned about? This is not something causing me to loose sleep (yet).

Here again, too many variables to take into consideration. I know some steamers that run 1x per month for 4 months during the Summer...with the boiler being drained between runs. Other steamers...running as much as 3x or 4x per month for as many running months as they can squeeze from early Spring to late Fall. Would almost believe...better care for a more frequently used boiler can outlast a boiler with less than desirable practices for an occasionally used boiler (have no data to substantiate that...but it could happen).

Internal water flow...having watched a local club member clean/de-scale a boiler with the steam dome removed...I can confirm the violent cyclonic water flow (rear to front) as the water is heated around the firebox, rises to the top, flows forward, cools and sinks to the bottom of the barrel to replace the water around the water legs. Not sure that flow could lift debris and deposit same on top of the crown sheet. Sorry, don't have that kind of background. In the Rutland boiler...if "sub standard steel" was used for the firebox, safe bet the same kind of steel was used for the girder stays implying lots of steel degradation.

Appreciate your thoughts on galvanic reactions. 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!
doublereefed
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Re: 730 Old Boiler Dissection

Post by doublereefed »

I came to own an Allen Mogul with boiler in unknown condition, other than that the blowdowns were blocked. I removed the dome, the boiler was FULL of scale. I just used water, no chemicals, and some tools and wire to start scraping and loosening things up. I built a water jet pipe that shot the water at a 90 angle to the entry on the blowdowns. I pulled piles and piles of what looked like potato chips out of that boiler... mostly with a vacuum but much of it with various magnet tools (magnet on a string, magnet on a stick, etc.) I got the blowdowns cleared again, but no idea how clean or clear the firebox water legs are. However, the point of that little story is that I threw a pile of those scale/rust chips into a bucket with CLR... and there wasn't a whole lot of metal in that pile. It was 90+ maybe even 95% scale... not rust. There was just enough steel in those chips to make them magnetic so I could fish them out. The boiler continues to pass inspections... it might last 1 year or 10 years, I don't know. During the first year of running the blowdowns would restrict with scale chips, I would knock them with a wire, and they would blast free. That isn't happening any more. Two other notes: I think the original owner would leave the boiler full of water after running, and the area he was in is known for very hard water. This could account for all that scale, also the price of the locomotive was commensurate with the fact that the boiler was in very bad shape.

In the annual hydros it will be interesting to see what eventually goes first on this boiler. (I'm almost looking forward to it because there's a lot of work I'm going to do when I have the boiler off of the frame.)
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Re: 730 Old Boiler Dissection

Post by rkcarguy »

ccvstmr wrote: Tue Oct 01, 2019 2:59 pm
rkcarguy wrote: Mon Sep 30, 2019 6:21 pm I just realized something, so this boiler (the cut apart one) was originally steel tubes and they were replaced with copper.
Copper and Steel are a fair distance apart on the galvanic reaction chart, i.e. the steel will be consumed as the "anode" in the "battery". Heat speeds the process, and the crown sheets close proximity to the copper tubes (and all the brass fittings and valves at the control end) and increased heat would have made those copper and brass items the perfect cathodes to eat away the steel. Furthermore, the firebox side tube sheet would have experienced vertical water flow as the water was heated, which probably swirled at the top depositing additional "stuff" on that shelf of a crown sheet.
RK...good points. While I've heard only occasionally of some boiler operators installing sacrificial zinc or magnesium rods in their boiler...would think the hobby as a whole (generally speaking) is going to be in a big hurt!

Most steel boilers are now being build with copper flues. At some point as the boiler is mounted and piped, there's going to be a steel to brass/bronze interface for pipes or other boiler accessories. Does galvanic decay occur at such a rate steamers need to be overly concerned about? This is not something causing me to loose sleep (yet).

Here again, too many variables to take into consideration. I know some steamers that run 1x per month for 4 months during the Summer...with the boiler being drained between runs. Other steamers...running as much as 3x or 4x per month for as many running months as they can squeeze from early Spring to late Fall. Would almost believe...better care for a more frequently used boiler can outlast a boiler with less than desirable practices for an occasionally used boiler (have no data to substantiate that...but it could happen).

Internal water flow...having watched a local club member clean/de-scale a boiler with the steam dome removed...I can confirm the violent cyclonic water flow (rear to front) as the water is heated around the firebox, rises to the top, flows forward, cools and sinks to the bottom of the barrel to replace the water around the water legs. Not sure that flow could lift debris and deposit same on top of the crown sheet. Sorry, don't have that kind of background. In the Rutland boiler...if "sub standard steel" was used for the firebox, safe bet the same kind of steel was used for the girder stays implying lots of steel degradation.

Appreciate your thoughts on galvanic reactions. Carl B.
I agree that a boiler used more often would probably fare much better, but more so it comes down to water quality and maintenance(drain and dry after each run). Debris lifting can and will happen with fine particles and minerals in the water used, my last home had very hard water and the water heater inside, faucets, and sinks/tubs always built up a white chalky layer around the water line that I had to clean up with CLR. Larger chunks of scale are of course going to sink. If you think about rusty water in a barrel, it's easy to stir up and takes hours to settle out so the water is clear again so fine particles can certainly be suspended in water. As far as galvanic corrosion happening, I don't think it's a huge issue as long as the water is drained and the boiler dried out after each use. The difference here is huge though. For example my boat has a old Volvo 4-cylinder engine, and the cast iron manifold I got on a parts engine from a great lakes boat that was 20+ years old and virtually spotless inside from fresh water and being drained after every use. When I purchased my boat, it was overheating and leaking because it had been poorly cared for and the manifold was so full of scale it was choking off the raw water flow exiting the exchanger and over-pressured the fittings causing leaks. This manifold casting was only 4 years old. Furthermore when I went to remove the bronze/brass fittings from the clogged manifold to transfer to the good one, many of the female NPT threads in the cast iron had simply been consumed by corrosion. So I think the biggest thing is to NOT leave the water in the boiler any longer than you have to, and if you have to(operating every day or every other day), a zinc anode would really help.
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