I am by no means an expert on this and my responses are based on my research. You should do what I plan on doing and that's to have a discussion with your local boiler inspector before making a purchase (new or used). The answers to these questions depend on which state you live.
I'll make the point once again. Even if a boiler isn't certified as a code boiler it still needs to be designed to those minimum standards and operated in the same manner (yearly inspections, etc). You also need to see how the boiler code for your state is written. Found in California's code "
(a) All fired pressure vessels shall be constructed, inspected, and stamped in accordance with the Code insofar as applicable. Those vessels not included in the scope of the Code shall be designed and constructed in accordance with good engineering practice regarding pressure vessel design for the pressure and temperature to be expected in service with a factor of safety of at least four.
(b) Good engineering practice as used in this article shall be construed to require the employer to provide details of design and construction which will be as safe as otherwise provided by the rules in the Code including shop inspection
I read this to mean that you can get a operating permit on a home built boiler as long as you can show that it is designed and built to the standards in the code (these would be the good engineering standards). It also appears that California exempts boilers with steam drums under 16 inches from annual inspection. This seems to be in line with Bart's postings
JonRiley56 wrote:1. If one acquires a used boiler, what kinds of "provenance" or proof do you need as to the integrity of the design and the quality of the build ? How does one know if there have been any modifications, repairs etc ? Could you in fact face a greater liability with a "tired" code boiler than with a fresh home built ? If the only in service test for biolers is hydro pressure testing and they both pass............how could you predict one might fail sooner than the other ?
Great answer from detroittug. You will face liability if you don't do you due diligence, You need to have an older boiler inspected by a qualified individual before operating the boiler. This would entail a though visual inspection. The inspector may request that an ultrasonic thickness test be done if there is any indication that there is any thinning. A code boiler will have a code stamp somewhere on the pressure vessel, if this is absent you may need to show proof that the boiler design was done to standard. And of course, a hydrostatic test will be done to 1.5 MAWP (higher pressure is not needed and could potentially damage the pressure vessel). Either way, a new boiler or used boiler, if it's not up to snuff it should never be fired up.
JonRiley56 wrote:2. Is there a difference between public and private use ? If it is not for hire etc are the regulations different. I believe in some activities there is a difference between "hobby" and "commercial".
Commercial use requires a higher standard. Code boilers and annual inspections are mandatory and there may be more. As far as "hobby" use is concerned; A power boiler is a power boiler, there is no distinction on use. There are miniature boilers that are exempt in some jurisdictions but the definition usually places this category outside of what would be useful to drive a steamboat. (Usually size and MAWP are restricted)
JonRiley56 wrote:3. Could one make the argument that the need for code assemply is directly proportional to the potential for injury/damage resulting from a malfunction and that therefore in decreasing need would be Fire Tube, Water Tube, and Monotube Flash ?
You could, but the regulating agencies don't. They already have definitions usually based on volume and working pressure. A flash boiler could fall into an exempted category based on volume but if it doesn't it still is under the jurisdiction of the ruling agency. And anyway all boilers still need to meet the minimum design criteria listed in the code to be considered safe. As Wesley pointed out, this isn't the end of the story, any boiler used improperly can (will) have issues.
JonRiley56 wrote:3. Is the code approved construction requirement just for the rpessure vessel or the entire assembly ? Is it conceivable to have someone build the pressure vessel part with the appropriate outlets etc and then finish the rest yourself ?
It's up to the first valve outside of the boiler. You will usually need to add the appliances, valves, safeties, water glass to the boiler but it depends on what you purchase.
JonRiley56 wrote:4. As an aside, I havent seen any talk in the marine boiler world of "fusible" plugs as sagety devices. Are they used and I have not noticed them, or are they particularly related to stationay steam like traction engines.
As far as I can tell, fusible plugs are not dictated by code and seem to be found mostly on locomotive style boilers.
Ken
For testing and similar considerations: check out the "FAQs" page on this website and view the "SAFE BOILER GUIDELINES" topic. Everyone reading this forum should do the same, even if you're not in the USA. 