peterl95124
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this is a rhetorical question about a problem that should be answered with engineering data.
Welding a copper boiler?
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this is a rhetorical question about a problem that should be answered with engineering data.
Should be de oxygenated copper, C106 here don't know what your code would be
peterl95124
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c122 plumbing copper is what we all use, about 99.9% pure, phosphorus de-oxidized high residual phosphorus. electrolytically purified fully de-oxidized copper, c101, is for electrical, more like 99.99% pure, c106 is in the later category so at least in the USA is what plumbing copper is made of.
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Sorry that should be de oxidized as you say not de oxygenated but the C106 is still the usually suggested grade.
I have the same thought. A walk through a food processing plant will likely have all kinds of stainless unfired pressure vessels working at all kinds of pressures. And I have seen at least one commercial boiler size of about 30000 lbs per hour and maybe 300 psig in operation. It was a rare one but it exists. Now it could be only the drum was stainless but I do regret now not to have taken a closer look. Was busy at the time and wanted to get what I had to do done so left it alone.
peterl95124
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I believe there's some UK - USA nomenclature issues, looking at applegate.co.uk
your C101 ETP (electrolytic tough pitch) is what we call c110 ETP, and is about 99.95% pure
our c101 OFHC (oxygen free high conductivity) is 99.99% pure for electrical wire
but your C106 DHP (phosphorus deoxidized) doesn't exist here, we use c122 (phosphorus deoxidized) which as near as I can tell is the same thing, at applegate its listed as a related specification (whatever that means).
here in the USA if you're buying sheet metal its mostly c110 and some c101, but as far as I can tell phosphor deoxidized isn't available in sheet.
here in the USA if you're buying tube/pipe its all c122. we would have to saw it and unroll it to make our own sheet.
Richard Hed
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If it was TIGged with the same material there would be no galvanic corrosion.
Richard Hed
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for one thing, if it is a water tube type boiler, it woud NOT explode. At most, a tube wou;d split and blow out a line of steam which could cut you in half, or a line of water that turns to steam as it blows out. But explode? Naught.
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The model live steam locomotive hobby is bigger per capital in England and they use copper boilers.
Yes, I also find it strange that quite a few people disagree with using stainless steel as a steam boiler
My goal is to make a steam train, and the boiler will definitely be stainless steel
Interesting to note a couple of comments in the paper:
https://www.materialwelding.com/stress-corrosion-cracking-scc/# "Even though SCC is a brittle kind of failure, the cracking hardly ever propagates rapidly enough to cause a catastrophic failure, even in the case of vessels which operate under pressure".
# "In austenitic stainless steels, SCC can occur in the unwelded parent material due to residual stresses from cold working or service stresses.
In the welded products where welding may add to the stresses, SCC can occur both in the parent plate and weld-metal. The most significant environment causing SCC is aqueous solutions of chlorides at elevated temperatures."
# "the preventive measure consists of avoiding the sensitization of the stainless steel by appropriate material selection or welding procedure control. Another effective measure is of course control of the environment." (I reckon many businesses capable of making certified pressure vessels in stainless steel will have suitable processes to minimise residual stresses in boilers and heat exchangers: But the "hobby" welder will probably not have such expertise and capability).
# "In the welded products where welding may add to the stresses, SCC can occur both in the parent plate and weld-metal. The most significant environment causing SCC is aqueous solutions of chlorides at elevated temperatures". - Thus, it would seem sensible practice to avoid TAP water that has been processed by the addition of Chlorine/chlorides and Fluorides. Natural rainwater should be OK in this respect.
"nuff said"?
K2
https://www.materialwelding.com/stress-corrosion-cracking-scc/# "Even though SCC is a brittle kind of failure, the cracking hardly ever propagates rapidly enough to cause a catastrophic failure, even in the case of vessels which operate under pressure".
# "In austenitic stainless steels, SCC can occur in the unwelded parent material due to residual stresses from cold working or service stresses.
In the welded products where welding may add to the stresses, SCC can occur both in the parent plate and weld-metal. The most significant environment causing SCC is aqueous solutions of chlorides at elevated temperatures."
# "the preventive measure consists of avoiding the sensitization of the stainless steel by appropriate material selection or welding procedure control. Another effective measure is of course control of the environment." (I reckon many businesses capable of making certified pressure vessels in stainless steel will have suitable processes to minimise residual stresses in boilers and heat exchangers: But the "hobby" welder will probably not have such expertise and capability).
# "In the welded products where welding may add to the stresses, SCC can occur both in the parent plate and weld-metal. The most significant environment causing SCC is aqueous solutions of chlorides at elevated temperatures". - Thus, it would seem sensible practice to avoid TAP water that has been processed by the addition of Chlorine/chlorides and Fluorides. Natural rainwater should be OK in this respect.
"nuff said"?
K2
Peter 195:
Your statement "My guess is the Brits simply don't want to go through the time and effort to establish a safety record with stainless for the necessary insurance, which is entirely understandable"
A good guess, and I suspect nearly all true. But we Brits have a working standard for pressure vessel and boilers covering all materials, and as Model Engineers have a "special clause" permitting Silver Soldered Copper Boilers for our model use to be outside some of the regulations. Probably because our laws are based on "precedent": If we have done it successfully for a long time and no-one got killed or maimed, then we can carry-on doing it - for now.
But until the last few decades, stainless steel was expensive, (e.g. In the 1970s most public toilets were glazed ceramic, now (I.E. this century) they are stainless steel - due to cost!), so when "expensive", Brits don't use it for their hobbies. Hence such boilers would have to comply to latest regulations for design, materials, manufacture, etc. - which makes them expensive, thus not first choice for hobbies.
And many of us have "Old blow-lamps" - or modern ones - for heating so we do not need to invest in expensive welding equipment for our silver-soldering. - Just a few fire bricks and a bucket of sand. Some of us like to retain and practice the skills we learned in the 1960s (or whatever century) and thus do not need "modern technology" for a practical result. Many models are made to maintain the memory of technology from decades and centuries past. - They were not intended to be made by "modern methods with modern materials, etc.". And they are for hobby use, not commercial duty, as reflected in the legislative special clause and insurances.
K2
Your statement "My guess is the Brits simply don't want to go through the time and effort to establish a safety record with stainless for the necessary insurance, which is entirely understandable"
A good guess, and I suspect nearly all true. But we Brits have a working standard for pressure vessel and boilers covering all materials, and as Model Engineers have a "special clause" permitting Silver Soldered Copper Boilers for our model use to be outside some of the regulations. Probably because our laws are based on "precedent": If we have done it successfully for a long time and no-one got killed or maimed, then we can carry-on doing it - for now.
But until the last few decades, stainless steel was expensive, (e.g. In the 1970s most public toilets were glazed ceramic, now (I.E. this century) they are stainless steel - due to cost!), so when "expensive", Brits don't use it for their hobbies. Hence such boilers would have to comply to latest regulations for design, materials, manufacture, etc. - which makes them expensive, thus not first choice for hobbies.
And many of us have "Old blow-lamps" - or modern ones - for heating so we do not need to invest in expensive welding equipment for our silver-soldering. - Just a few fire bricks and a bucket of sand. Some of us like to retain and practice the skills we learned in the 1960s (or whatever century) and thus do not need "modern technology" for a practical result. Many models are made to maintain the memory of technology from decades and centuries past. - They were not intended to be made by "modern methods with modern materials, etc.". And they are for hobby use, not commercial duty, as reflected in the legislative special clause and insurances.
K2
Carbide precipitation comes to mind with stainless steels. Thats why many grades have an "L" suffix to there grade (ASTM austenetic grades). Having said that elevated temps for to long a period will cause carbide precip and the stainless will rust. Many guys weld either to hot or to cold and with a very slow travel speed inputting way to much heat and then continue welding without maintaining an interpass heat of about 300F.
Having said that I've tig welded type "k" copper pipe to copper fittings with argon and turned out visually acceptable.
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Does visually acceptable mean it looks good from the outside, but not so much from the inside? Were the welds structurally acceptable to you?
Bentwings
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As far as welds go the coupling to pipe joint would be classified as a lap joint or if it were carbon stainless or any other material it would be called a "socket weld" which uses a fillet weld to fuse the two together.
Being a pipewelder by trade and looking at the exterior and interior I would say that is an acceptable weld visually. However unless tested for mechanical qualities through destructive testing the visual means nothing
Bentwings
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When I inspected a weld the visual look gave me an indication of the skill of the welder but did not confirm the weld was good. I would look for under cutting, spatter, weld pattern, and usually but not always it was the first indication of a good or bad weld. I also knew I would not be able to check the porosity or penetration of the weld without testing. Now I have also seen ugly looking welds that passed with flying colors. But more often then not a weld with defects on the surface also has defects underneath. But unless you know and understand what you are looking at the visual can mean nothing. As one old welder told me once " I can make this look pretty or make it to hold I made it to hold."
A strange experience:
I experienced a weld - from a factory process, with speed controlled and jig held MIG torch, so gas, feeds and speeds, etc. all calibrated and set, and batch recorded.... but of thousands of welds joining structural end fittings to steel tubes, one single end casting had some "contamination" so the weld that looked as perfect as the rest had zero penetration into the casting. Sent to the Welding Institute for a report on "Why? and what went wrong?" they were completely bamboozled. This was not a pressure weld, but a tension member: When the load was applied as the structure was assembled, a ring of unwelded steel casting appeared as the end piece pulled-out of the tube. Micrograph sections showed perfect penetration and welding to the tube and a non-welded friction joint between the weld and the end casting. The report suggested the end casting may have been simply VERY cold, or had some insulating pollution (Oxide?) on the surface that prevented the arc from "hitting" real metal so the feed metal "spray" simply sat on the surface of the end casting. Further metallurgical lab studies had failed to find any contamination, so the Welding Institute report had "no conclusion" for the failure. - Had this been a pressure vessel shell, pipe-joint or whatever, the pressure test would have definitely exposed the faulty weld. The Company had stringent checks in place, so all welded and bolted joints were examined for movement as the structure was built and during loading up to completion. These checks had identified the failure part way through construction of the building. No other faults were found.
Conclusion. A visually externally perfect weld can have a total failure within. But if it "holds the load without failure", then it can be deemed OK. - Except the "Factor of Safety" may be compromised.
For Boilers in service, the equivalent loading "to ensure safety" is the periodic Hydraulic test at an excess well above the Safety valve release pressure. (ASME and UK regs require different pressures, but both have "Excess" pressure applied hydraulically).
I personally feel that there can be many boilers "in service" where joint integrity is "Imperfect", even by design, such that an over-pressure of the boiler could fail a joint at well below the "design expectation". The Safety valve must therefore be suitably respected and checked against the gauge at every steaming to be sure that boilers cannot experience adverse conditions. ALL Boiler operators MUST also be well trained and "compos mentis" when operating boilers to prevent operation outside the correct operating limits.
(compos mentis: = (law) Of sound mind, sane; thus criminally responsible for one's eventual wrongdoing).
K2
I experienced a weld - from a factory process, with speed controlled and jig held MIG torch, so gas, feeds and speeds, etc. all calibrated and set, and batch recorded.... but of thousands of welds joining structural end fittings to steel tubes, one single end casting had some "contamination" so the weld that looked as perfect as the rest had zero penetration into the casting. Sent to the Welding Institute for a report on "Why? and what went wrong?" they were completely bamboozled. This was not a pressure weld, but a tension member: When the load was applied as the structure was assembled, a ring of unwelded steel casting appeared as the end piece pulled-out of the tube. Micrograph sections showed perfect penetration and welding to the tube and a non-welded friction joint between the weld and the end casting. The report suggested the end casting may have been simply VERY cold, or had some insulating pollution (Oxide?) on the surface that prevented the arc from "hitting" real metal so the feed metal "spray" simply sat on the surface of the end casting. Further metallurgical lab studies had failed to find any contamination, so the Welding Institute report had "no conclusion" for the failure. - Had this been a pressure vessel shell, pipe-joint or whatever, the pressure test would have definitely exposed the faulty weld. The Company had stringent checks in place, so all welded and bolted joints were examined for movement as the structure was built and during loading up to completion. These checks had identified the failure part way through construction of the building. No other faults were found.
Conclusion. A visually externally perfect weld can have a total failure within. But if it "holds the load without failure", then it can be deemed OK. - Except the "Factor of Safety" may be compromised.
For Boilers in service, the equivalent loading "to ensure safety" is the periodic Hydraulic test at an excess well above the Safety valve release pressure. (ASME and UK regs require different pressures, but both have "Excess" pressure applied hydraulically).
I personally feel that there can be many boilers "in service" where joint integrity is "Imperfect", even by design, such that an over-pressure of the boiler could fail a joint at well below the "design expectation". The Safety valve must therefore be suitably respected and checked against the gauge at every steaming to be sure that boilers cannot experience adverse conditions. ALL Boiler operators MUST also be well trained and "compos mentis" when operating boilers to prevent operation outside the correct operating limits.
(compos mentis: = (law) Of sound mind, sane; thus criminally responsible for one's eventual wrongdoing).
K2
HMEL: Your comments are probably the most pertinent of all - and should be read slowly and carefully by all weld inspectors... "When I inspected a weld the visual look gave me an indication of the skill of the welder but did not confirm the weld was good. I would look for under cutting, spatter, weld pattern, and usually but not always it was the first indication of a good or bad weld. I also knew I would not be able to check the porosity or penetration of the weld without testing."
Thanks,
K2
Thanks,
K2
