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Author Topic: Boiler corosion too bad to use?  (Read 973 times)

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Boiler corosion too bad to use?
« on: December 07, 2021, 05:08:18 pm »
Just bought a 9 year old PM research boiler, that I am discovering issues with. When removing the blow down plug, it is clear that the plug was not often used. There was a bit of corosion on it, but the biggest issue was that the plug is very brittle and looks as if all the metal was eroded away except for a copper "framework" that is very brittle. Plugs aren't that big of a deal, but that got me thinking about the boiler bushings. Upon inspection with a borescope, it is clear that the bushings are also very brittle (at least on the blow down) I don't imagine there is an easy way to replace this bushing, so I assume my options are to accept that I wasted my money, or pressure test it and confirm if it can or cannot stand up to 1.5 or 2 times the operating pressure.i would love to hear if this is something that others have successfully reworked without unsoldering the whole darn thing.
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Re: Boiler corosion too bad to use?
« Reply #1 on: December 07, 2021, 05:48:57 pm »
Hi,

That looks like a classic case of de-zinc caused by exposing BRASS bushes and fittings to hot steam and water.

The bushes and all fittings, or at least the threaded portions of fittings, should be made from BRONZE.

The only way you can remedy this is to drill out all the bushes and fit new ones made from BRONZE and silver braze them into position.

I would not recommend that you steam it whilst in current condition since if one of the bushes gives way under steam pressure you will get a rapid expansion and ejection of very hot scalding water, which can travel a lot further than you would imagine and could well injure someone.

Where are you located?... if you are in the UK I may be able to make you some new BRONZE bushes.

I hope this is of some help.

Sandy.

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SandyC      West Coast of Scotland.
“Don’t think about your errors or failures; otherwise, you’ll never do a thing.” Bill Murray.

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Re: Boiler corosion too bad to use?
« Reply #2 on: December 07, 2021, 07:43:18 pm »
I'm always looking for used PM stuff. If you don't want to mess with repairing it and you're in the US, I might be interested in it. Let me know how much you might want.
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Re: Boiler corosion too bad to use?
« Reply #3 on: December 07, 2021, 08:35:34 pm »
"That looks like a classic case of de-zinc caused by exposing BRASS bushes and fittings to hot steam and water.

The bushes and all fittings, or at least the threaded portions of fittings, should be made from BRONZE."

I have many 50-70 yr. old Jensen's with all Brass boilers and threads as well , with no signs of erosion and very little wear , am I missing something ?
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Bruce, St. Paul Indiana, USA
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Re: Boiler corosion too bad to use?
« Reply #4 on: December 07, 2021, 11:49:52 pm »
I suspect the reason may be Chloramines from tap water. In talking with a metalurgical budy, this can be a large issue for plumbing components made with pure brass. Had the engine been run on distilled or DI water without the chlorine, it may not have degraded. I put a tool in and flaked some of the bushing out with light pressure. I do not have the means to say how deep the metal has been affected, or if the soldered joints are near the degradation. I may make this boiler available for sale, I need to think through what this rework would take, and if I have the time. I am located in the US but I appreciate the offer Sandy, I may still be willing to buy/ship some over the pond. Enginerd, if you have an idea what this boiler is worth to you, that is a better base than my limited exposure to pm research prices. Feel free to shoot an offer in PM if you want, I'm definitely still weighing my options right now.


It's a non-rivited boiler if that is of interest, I was a little surprised by it. [ Guests cannot view attachments ]
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Re: Boiler corosion too bad to use?
« Reply #5 on: December 08, 2021, 06:24:44 am »
Quote from: St Paul Steam on December 07, 2021, 08:35:34 pm
"That looks like a classic case of de-zinc caused by exposing BRASS bushes and fittings to hot steam and water.

The bushes and all fittings, or at least the threaded portions of fittings, should be made from BRONZE."

I have many 50-70 yr. old Jensen's with all Brass boilers and threads as well , with no signs of erosion and very little wear , am I missing something ?

Hi Guys,

De-Zinc is caused by an electrolytic reaction between the Zinc in Brass acting as an anode and the very much larger area of the Boiler body being made from Copper (a more noble metal)acting as the Cathode in conjunction with hot, often acidic water such as rainwater, or tap water which contains Chlorine etc, acting as the electrolyte.
It can be more pronounced in boilers that are left partially filled and not drained down and dried fully after use.

St Paul,

If the boiler and bushes are both made from Brass then the problem is largely eliminated as there is very little electrolytic action, although there is still some, since Brass is largely Copper with some Zinc added, and can often appear as small brownish spots on the surface, this is especially so if the boiler is not drained and dried properly after use.
Boilers, bushes and fittings made from DZR Brass (De-Zinc Resistant) are generally immune to this problem.

MadeForThat,

Your metallurgical buddy is quite correct, and YES Pure distilled water (PH Neutral) is the best type of water, with DI as a second option, although this too can cause some issues with ion exchange problems.

That is a nice looking boiler and I am sure it could be restored by fitting new bushes and fittings, however, it would need to be done by someone with the correct equipment and skills.

I wish you good fortune whichever way you choose to proceed.

SandyC (retired boiler maker).
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SandyC      West Coast of Scotland.
“Don’t think about your errors or failures; otherwise, you’ll never do a thing.” Bill Murray.

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Re: Boiler corosion too bad to use?
« Reply #6 on: December 08, 2021, 08:45:50 am »
Sandy, as a retired boilermaker, what do you figure this kind of rework would cost if done by someone with the proper skills? I am always willing to try to learn a new skill, but my soldering experience is purely copper pipe and electronics, and silver solder uses so much more heat. I think from using the borescope that only the 2 bottom bushings were effected, the bottom sight glass bushing is in much better shape and I would feel fairly confident with it, but if someone is going to strip the paint and drill one out, might as well do both. Thanks for the input, I wish this is something I could have identified before I bid as high as I did, but it can't be changed now :)
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Re: Boiler corosion too bad to use?
« Reply #7 on: December 08, 2021, 12:12:39 pm »
Hi,

Hard to be too specific, but I would think that given the time needed to strip the paint,drill out all the old bushes, clean up the boiler shell, make new bushes from Bronze, Silver Braze them all into position, clean up the flux residue and retest the boiler to 2 x working pressure then repaint, I do not think you would get much change from $100 - $150.00... there is quite a lot of work involved... a good 3-4hrs + paint drying time... it would largely be determined by how many bushes required replacement... if it were mine, I would replace the lot and be done with it.

I hope this helps.

SandyC.
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SandyC      West Coast of Scotland.
“Don’t think about your errors or failures; otherwise, you’ll never do a thing.” Bill Murray.

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Re: Boiler corosion too bad to use?
« Reply #8 on: December 12, 2021, 09:09:53 pm »
If you are going to use anything except distilled water or RO water, add another threaded bushing below the water line for a sacrificial rod. Both of my steam locomotive boilers have sacrificial rods and they do erode and have to be replaced. This because the boiler is steel and the tubes are copper.
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Re: Boiler corosion too bad to use?
« Reply #9 on: December 13, 2021, 11:38:54 pm »
Keith is sometimes a little over the top but has some very practical, down to earth techniques. Here he covers boiler repairs.

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Re: Boiler corosion too bad to use?
« Reply #10 on: December 18, 2021, 07:14:59 pm »
Welp I ordered a map torch and a book written by Alex Weiss/Kevin Walton about making small steam boilers! I will drill out these bushes to the OD of the replacement bushes that are in the mail
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