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My Garn Corrosion Fiasco Part 1

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by Rick Stanley, Feb 6, 2011.

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  1. bpirger

    bpirger Minister of Fire

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    Here's another question for the newer Garn owners.....or all for that matter. Was the entire bottom surface of your tank covered in the white epoxy "paint"? Do you have a 2000, 1500, 3200, etc?

    In my 1500, I only had the "paint" under the sacrifical rod....not covering the entire length of the unit. This surprised me somewhat....I'd think covering the entire bottom where whatever sludge will sit is good. But perhaps they only coat under the sacrificial rod, as if somehow the pieces of rod drop down directly below?

    Perhaps I should have been more proactive about this before forging ahead with installation and fill.....

    So what do you have? Full covering or just partial, and what size unit?

    My plan is to take some photos of the inside of the Garn, the water, the corrosion, and try and get the camera "looking up" at the top side of the tank. Perhaps we can all post our current status to get a feel for what everyone has. Nothing like a little experience to know what to expect as the norm.....

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  2. Jim K in PA

    Jim K in PA Minister of Fire

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    Trevor, your comment is what I have been thinking all along. There is no way you can completely prevent corrosion from occurring in a mild steel tank filled with water and some amount of oxygen. ALL metals can and do corrode. Heck, I have taken pictures of corroded welds inside a "stainless steel" tank on a fire department water truck. Zinc and copper, two highly "corrosion resistent" metals, actually RELY on the formation of an outer layer of zinc or copper oxide to slow the progression of corrosion. Have you ever seen an old steel car fender out in the field from the 1920s? Brown with rust, but that outer layer of FeO2 has actually protected the core metal from rapid, progressive corrosion.

    Now, I am not saying that anyone, me included, wants a big rusty tank of water. But, I surely do NOT expect my GARN to remain "rust free" no matter how many tests I perform or additives I add. Conversely, bacteriological corrosion can be insidious, and as mentioned in the manuals, can be vigourous enough to pit through a tank wall in months and must be dealt with quickly and aggressively. The photographs Rick took are good, but I cannot discern any particular features that would cause ME concern about imminent or even distant failure. But his actions were sound, and his decision to share his experience commendable.

    If anyone does find localized corrosion in their storage tank, GARN or other boiler, clean off the loose material and try to get a gage measurement of the depth of the pit. That is the only way to really know what, if any, real damage has been done.
  3. jebatty

    jebatty Minister of Fire

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    Do some reading on the difficult issues presented by the range of biological corrosion and you will find there are no easy or necessarily inexpensive remedies, and this is not likely to be "protective rust," but corrosion protected by the surface corrosion which continues to eat away underneath. I understand that in extreme cases 3/16" steel could be penetrated in a few weeks.

    My post above on my old OWB describes a bladder expansion system, but also the boiler had a weighted vent that maintained, with the bladder, about 2 psi in the system. I doubt the water jacket ever had much, if any, free air space, as that was filled with water as the water jacket cooled and the water expansion flowed back into the water jacket. So I guess this might have been a hybrid open/closed system with very low pressure. Others may have the same type of boiler.
  4. heaterman

    heaterman Minister of Fire

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    Just a FYI and a story to illustrate what can and sometimes does happen.

    A very large midwestern city ceased adding chromate to their boiler water supply when the use of them was banned. The chromate (probably zinc chromate) was specifically introduced into the water to prevent bacterial corrosion in piping and other vessels. Long story short, during the first heating season, 30% of the boilers in city owned buildings failed due to corrosion that was found to be bacterially related. These were all closed system boilers, and I didn't hear it said during the telling but I would bet they were all steam boilers that of course, ran above 212*.

    I'll say this again here for some who have missed it previously.

    190* in a Garn, a storage tank or any other open system is not an issue. BOILING the water is the issue that drastically changes PH levels due to a host of factors. Biological contamination being only one of them.
  5. Rick Stanley

    Rick Stanley Feeling the Heat

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    Ok, so that means we shouldn't BOIL a Garn. Because there might be a dead mouse in there:). Right? It says on page 5 of the manual that I have, that if you build a fire in a Garn when the water temp is at 185 that you will approach the boiling point of water and water will come out of the overflow pipe and that is a "nuisance, wastes energy and evaporates water from the tank". Maybe it should say "HOLY CRAP STUPID FARMER DON'T EVER EVER OVERFIRE" just sayin
  6. Kemer

    Kemer Member

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    Mine is only coated under the rod.I also agree with heaterman and Jim K on there comments
  7. Rick Stanley

    Rick Stanley Feeling the Heat

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  8. Der Fuirmeister

    Der Fuirmeister Member

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    Our 1500 purchased in 2009 was not completely covered. Only under the rod.
  9. Rick Stanley

    Rick Stanley Feeling the Heat

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    Mine is a 2000, bought in 2008, the whole bottom is covered
  10. heaterman

    heaterman Minister of Fire

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    LOL I can ask Martin and see if they can make that change in the manual.

    In regards to temperature(s)......bear in mind that the temp you are seeing on your gauge is measuring at that one particular point. It would be logical to assume that variations can and do occur throughout a boiler. especially one the size of a garn. I use 190 as a reference point of my own recommendation to allow some margin for error on the gauge as well as variation in the tank. The issue is and always will be actually getting the whole mess to the boiling point. As we all understand now, it's something to be avoided.

    This has been a good learning experience for everyone involved. I've looked up stuff and read stuff and learned stuff about water quality that I never would have realized otherwise.
    Talking with Mike yesterday, it became pretty clear that there are so many variables involved with incidents like yours that pinpointing any one thing that caused it is almost impossible. I have to admit that while I knew elevated water temps can possibly cause problems, I never really understood the mechanisms that make it happen. Now at least I know a couple out of the hundreds. One other thing that I'm beginning to understand is that if manufacturers put all the stuff that can happen into the owners manual, it would take up more space than the boiler itself. No one would ever buy a wood boiler just from the shock of the manual. ....kinda like having kids. If we knew what we were getting into when we had 'em we'd have thought twice about it. :)

    I just want to thank you again Rick, for bringing this up in a forthright and candid fashion. It helps us all.
  11. nt30410

    nt30410 Member

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    Manuals are suggesting 185*F the max.......others are saying the chemicals are breaking down at 190*F.....and yet I am told the new controller has a sticker advising not to exceed 200*F. This is confusing. To correct the new manuals will not accomplish much for those owners who have older units with older manuals. If any changes are made to manuals then an addendum should be sent to all so they can up date their manuals which could be the difference between a healthy or dead boiler.
  12. Willman

    Willman Minister of Fire

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    I realize elevation affects boiling point. Doesn't pressure raise it also? A closed system that loses power and is at the beginning of a burn without enough dump zone could boil real quick setting off the MRSA of steel. Anyone know what a closed system boils at an average seal level?

    When heaterman mentioned the boilers prolly being steam I wondered how many years ago the dead men handled water quality within their systems. Did they use the banned chemicals back then an not have any of the bacteriologic issues or did they ? Or is the bacteria that is around a new strain brought on my "modern living"

    Will
  13. heaterman

    heaterman Minister of Fire

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    Elevation, as in higher elevation lowers the boiling point of water.

    A closed system at sea level pressure will boil at 212*F/100*C. One could get into a circular argument and say that once it starts to boil the pressure will elevate in a closed system thereby raising the boiling point......... But at 10PM after a long day I ain't gonna go there.

    AFA your last question is concerned, that is a very good one. I think that it would be very educational to ask it over at heatinghelp.com from the people who hang out on "the Wall". If anyone would know over there it would be Steamhead or Dan Holohan himself. Those two guys have more knowledge of old steam systems than anyone I know.
  14. heaterman

    heaterman Minister of Fire

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    I can spout this, that and the other thing based on my experience but in the end, regardless of whose equipment you have, follow the manufacturers recommendation. The manual is your friend.
  15. Como

    Como Minister of Fire

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    Technically boiling point is a function of pressure rather than altitude.
  16. heaterman

    heaterman Minister of Fire

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    Noted and corrected........

    Elevation, as in higher elevation lowers the boiling point of water due to reduced atmospheric pressure.
  17. Willman

    Willman Minister of Fire

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    Existing post on heating help from the steam thread.
  18. Willman

    Willman Minister of Fire

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    Searching existing threads on heating help found this
    Will
  19. Frozen Canuck

    Frozen Canuck Minister of Fire

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    I think were starting to mix apples & oranges here. The 2 references are from posts about steam boilers. They are different beasties than a water boiler. One always makes steam the other never should. Hence the different (change in) chemistry in the water as some of the replies in this post allude to when steaming/boiling occured, as well as all the possible sources of contamination that are present on a farm that may have also altered water chemistry. I have to agree with other posters in this thread that if it was a bacteria...well there are just far too many of them to justify the cost of testing to find out which one(s) did the deed. Far better from both a time & cost perspective to do a total kill then, clean-test, flush-test, then start the process of balancing the fluid & take more care so as not to boil/steam in future. Great thing about this thread is that we all get a lesson in why not to make, what are probably common mistakes for many members. Plenty of threads here about the "oops overfired my particlar brand" yesterday.
  20. jebatty

    jebatty Minister of Fire

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    Another idea on keeping the Garn filled with water to prevent empty air space. Might the Garn overflow be plumbed to the bottom of a vented tank, which could be installed at the same level as the Garn, so that the vented tank would accept Garn overflow water, and the vented tank then also would backfill the Garn as the Garn cools down; that is, water in the Garn contracts as it cools, vacuum in the Garn pulls water from the tank back into the Garn?
  21. Kemer

    Kemer Member

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    When I received my Garn I was very disappointed in the fact that it was shipped with out any coverings on the openings.It states in the Manuel to keep it clean yet they ship it open to the elements.If it so important to keep it sterile why don't they do a better job of shipping? Some plastic would of kept the leaves out of mine and saved me some work.
  22. woodsmaster

    woodsmaster Minister of Fire

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    Just a guess, but I'm guessing it may condensate and cause surface rust if all closed up and the temp changes.
  23. TCaldwell

    TCaldwell Minister of Fire

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    check out www.ceram-kote.com the product is ceram-kote 2000, upon talking to the mfgr, for boiler water treatments it is rated to 350degf, also www.dampney.com the protexier system using the 795 primer and 794 topcoat. there seem to be several products mostly sharing novalic epoxy as the primary component., Precision chemical says this practice is not uncommon.
  24. TCaldwell

    TCaldwell Minister of Fire

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    Well notwithstanding the isolated bacterial incidents but the overfiring issue of the condensate turning the water acidic, there are probably enough reasons not to fire above 190+/- anyway, primarily reduced heat absorbsion capability, ie lower effiency. It would probably be more productive to re-evaluate lower supply water temps, emitters, mixing, injecting, reset ect. brings to mind a neighboring garn owner who had the luxury of owning a garn before building his second house. his supply temp is 90degf he gets around the dwh issue simply by preheating his indirect fired hwh to 90 then feeds a elec hwh, to bring it up to 125 deg. this might not be attainable for most but there are probably areas that in most of our systems that gains could be had with a lot less risk. since my garn is parked in the garage and has to be cleaned anyway, I will probably do more research on coating the inside of the tank, unless proven to be detramental, as i have already voided my warranty many times over.
  25. steam man

    steam man Minister of Fire

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    I would almost think that a high level coating application is going to involve some serious prep work such as sandblasting. If that 190F is such a critical number to maintain and a garn shouldn't be "shutdown" while firing wouldn't it be an idea to think about installing a heat dump mechanism? I use a Modine heater on my solar system when the tank gets to 165F and it works great. Keeps the tubes below 200F easily. Granted it would have to be a big one.
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