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  • boiler plate

    i got a call to repair a wood boiler stove.when i looked at the material (i was told by the manufacturer it was boiler plate) it seemed to be fatieged from the wood side not the water side. what would cause this?the material was smooth on the water side but very choppy on the wood side.the stove is only 2 years old . any help is much appriciated.

  • #2
    Since no one else has touched this yet, I'll give you my best guess I can without having seen the piece:

    This is an educated GUESS

    It is corrosion from the combustion gasses and combustion gas condensate. This is a common problem with wood, especially with certain types of wood.

    It tends to be less of a problem with clean, seasoned hardwoods than with pitchy, acidy softwoods (many pines). Barked woods tend to be less of a problem as well.

    It can be controlled, to a point, when firing less desirable wood by maintaining the proper air mix, proper overfire air (enough to combust the gasses thoroughly, but not enough excess to cool the gasses), keeping the firebox clean, but not shiney (a very thin coat of soot helps protect the surface, but more than a very thin coat inhibits heat transfer), and by being sure that stack condensate doesn't run back into the firebox. On a boiler, especially low pressure or atmospheric pressure boiler, it can be tough, since the sheet temperature can't get too high in normal operation (the water on the wet side keeps the sheet cool by taking the heat)

    If the fire is run with excess air, the material could have just burned (oxidized, rusted), with the oxide breaking off and ending up going out with the ash, especially if the wood is wet or very dirty (lots of moisture and corrosives in the combustion gasses)

    Corrosion will be more pronounced where a sheet has been bent (knuckle corners, bumps on bump-bent material, etc) being more of a problem with higher strain bends, such as hard corners and bend points on a bump-bent cylinder. Cylindrical sections should be rolled for this reason, and hard corners should generally be welded with a proper joint design rather than flanged or bent (there are exceptions, but design and manufacture process is very important, including appropriate material selection and stress relief).

    The corrosion tends to grow from start points (several mechanisms: water side you get electrolytic cells at pits due to concentration of impurities in the water where the pits begin. It can be similar on the fire side, but there are other mechanisms as well), and may run in lines rather than pits (condensed corrosives run due to gravity and may be pulled by moving gasses), and if there is a waterline on the sheet, the temperature differential due to the difference in cooling (water cools the sheet well, steam doesn't much), stresses can be set up that give corrosion lines parallel to the water line. The wastage will also follow lines where the material has been distressed (in manufacture or in service)

    Look for indications that condensate has been running on the sheets or back out the stack (water, creosote, etc), as this is an indicator that firing and fuel are likely contributors.

    If the material is 'boiler plate' and the piece is two years old, it is likely a low carbon steel such as SA516. Weldable with E7018 or TIG 70s-2 (not -3 or -6... -2 is lower silica). If the boiler is ASME or is operated at pressure above atmospheric, check carefully to see if there are jurisdictional requirements for the repair (requirement of an R-stamp from NBIC or state) for the unit before doing repair.

    Welds should be full pen with a clean, flush root side. No lack of fusion at the root (a place for cracks to run, corrosion to start, and cells for chemical attack). If sheets are replaced, they should be rolled, not bump-bent, and about a thousand other details.

    For small amounts of wastage on material of sufficient thickness, pad welding to bring hte material back to thickness is ok (NBIC requires at least 60% of original thickness, but on material less than 1/4" thick I would replace it)

    I would check the material for embrittlement or carborization before welding it.

    THis ended up much longer than I intended, but is at best a rough summary. There is a LOT more to consider. If you can come up with pictures, more detail of the design and service, etc, I, and others here, can probably give better responses.
    I may not be good looking, but I make up for it with my dazzling lack of personality

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    • #3
      boiler plate

      thank you for the response.the repair i made was with 517 material.the origional material i don't know but its supposed to be boiler plate.i rooted with 6011 and capped with 7018.the material that was removed was sent to the manufacturing plant for testing.but the stove is still unoperatable because of more damage in all corners and fatiege of the steel.i sent faxes to the manufacturer saying the stove is to far gone to be repaired and to give the customer a new stove but that will be a fight.thanks again

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      • #4
        Originally posted by enlpck View Post
        Since no one else has touched this yet, I'll give you my best guess I can without having seen the piece:

        This is an educated GUESS

        ....

        THis ended up much longer than I intended, but is at best a rough summary. There is a LOT more to consider. If you can come up with pictures, more detail of the design and service, etc, I, and others here, can probably give better responses.
        Excellent response, Enlpck, teachers do tend to get wordy, but that's a gift that makes them able to communicate. I always enjoy your posts. Good job.

        dsweld, I think you did the right thing to hand that problem to the manufacturer...I wouldn't have tried to even fix it...too much liability involved.

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        • #5
          boiler plate

          well rocky i did end up putting 6" x 12" patch on the stove being that a family was out of heat.the patch was on the bottom of the stove and was a place that was a pain.as soon as the stove was patched we filled it with water and all the other leaks started to show.... i then said get a new stove or replacement.my patch was textbook repair,the stove is to far gone for further repair.the only problem i have is getting paid from the manufacturer.it will all work out in the end i hope.have a merry christmas, god be with everyone. thanks

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          • #6
            Originally posted by Rocky D View Post
            Excellent response, Enlpck, teachers do tend to get wordy, but that's a gift that makes them able to communicate. I always enjoy your posts. Good job.

            .
            I always like Eric-o-pedia over Wickopedia.
            Masterfly writen.
            vg
            sigpicViceGrip
            Negative people have a problem for every solution

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            • #7
              Originally posted by dsweld View Post
              well rocky i did end up putting 6" x 12" patch on the stove being that a family was out of heat.the patch was on the bottom of the stove and was a place that was a pain.as soon as the stove was patched we filled it with water and all the other leaks started to show.... i then said get a new stove or replacement.my patch was textbook repair,the stove is to far gone for further repair.the only problem i have is getting paid from the manufacturer.it will all work out in the end i hope.have a merry christmas, god be with everyone. thanks
              Maybe make sure they don't burn the trash in there too,
              before rubbing against the man'f'r.
              Some farmers do this.
              vg
              sigpicViceGrip
              Negative people have a problem for every solution

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              • #8
                boiler plate

                i don't think any garbage was burned but the hole thing top to bottom is just shy of rot.i put burnables in my stove in the shop and thats 5 years old no rot on that one. who knows they could have burnt tires all this time i never saw the stove even work just tried to repair ......... thank you for all the input vicegrip

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                • #9
                  If that stove was only 2 years old and it's already rotted out that tells me something is wrong.
                  Outdoor wood fired water heaters run at atmospheric pressure (no pressure).
                  What water are they filling the stove with? Out of a well? Hard water?
                  These stoves need to have good clean demineralizated water in them. Good clean water is the number one cure for corrosion in these stoves.
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                  • #10
                    boiler plate

                    well snoe,the water has to have the right ph level as i understand it inbetween 7-9.the company that installs the stove tests all that before filling.in my opinion the stove failed from the wood side and not the water side.the plate is very very fatieged from the wood side so bad that you can stick pencils in the holes.it is supposed to be boiler plate 1/4'',i had a hard time tying into anything above 1/8".the owner is struggling with getting anything out of the manufacturer as far as a new stove.i'm struggling to get paid........the owner is basicly running off little heaters to stay warm,i offered to weld the stove to get them heat but we're affraid this might hurt them in the long run....

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                    • #11
                      I understand where your coming from. I am a licensed operating engineer myself.
                      I used an outdoor wood fired boiler (hot water heater) to heat my house for years in the past.
                      Your correct on the PH requirements for the water. But....all it takes is a power outage (water no longer circulating) or the door being left open (too much air) and forgotten about, then the stove boils over, basically overheats, runs the water level down lower than it should be ran at. This happened to me much more often than one would think it would. That puts major stress on the metal in the stove unless it's refilled immediately. All these stoves I have seen all have a make up water valve in the system that will fill the system with the household water. My old Dahl boiler never had a water level sight glass on it so I made up a dip stick to dip the stove on a regular basis to check water level. I also used condensed steam (very clean water) from the power plant I work at in mine.

                      In my opinion, just because you see corrosion on the fire side of the stove doesn't necessarily mean it's the wood that caused it. What you can't see is the corrosion on the water side of the stove. In my opinion, there's no way a new stove like this will rot out in 2 years from the wood being burned in it. I used to burn all and every kind of wood in mine, anything I could get my hands on. Lots of pine and lots of birch.
                      May I ask what brand of stove this is? The new Central Boilers and and Crown Royal boilers have 25 and 20 year corrosion warranty on them respectively. For the price you pay for these units (they are not cheap), they should have a guarantee like that.

                      enlpck listed some good points.
                      Last edited by snoeproe; 01-12-2010, 11:12 PM.
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                      Thermal arc Hefty 2 feeder
                      Thermal Dynamics Cusmaster 52
                      Torchmate CNC Table

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                      • #12
                        boiler plate

                        the stove may have run low on water i don't really know i don't own it just repaired it.the stove has a 20 year warranty but its not going anywere..i will post pics and the name of the company as soon as i get paid.the manufacturer sent the owner plate for more repairs but refuses to pay more $$.the stove is defective in oneway or another, i suppose legal action is going to be taken.its just a shame a family spent alot of money for the stove and it only lasted two winters.now theyre fighting to stay warm in 0 degree weather.

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                        • #13
                          Interesting...The stove has a corrosion warranty and all the manufacturer does is send more plate? Ya, I feel for the family, for sure.
                          I hope that for the time being they have the stove drained, along with the two water lines going to and from the stove. With the cold temps, I'd hate to see anything freeze and break and thus create even more problems for them. Unless they have a good concentration of glycol in the water that's still left in the system.
                          Last edited by snoeproe; 01-14-2010, 08:23 PM.
                          Lincoln Idealarc 250
                          Miller Bobcat 250
                          Thermal arc Hefty 2 feeder
                          Thermal Dynamics Cusmaster 52
                          Torchmate CNC Table

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