Boiler Material: Difference between revisions
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: Seamless pipe, SA106B, would be my first choice for the shell. Flat plates should be Pressure Vessel Quality, SA516-Gr70 is the most common. Couplings and half couplings should be 3000# forged steel, ASTM A105. Stays and mudrings can be made from SA36. | : Seamless pipe, SA106B, would be my first choice for the shell. Flat plates should be Pressure Vessel Quality, SA516-Gr70 is the most common. Couplings and half couplings should be 3000# forged steel, ASTM A105. Stays and mudrings can be made from SA36. | ||
: 10" pipe is 10 3/4" OD. In a boiler this size I usually use 5/16" plate. | : 10" pipe is 10 3/4" OD. In a boiler this size (41-inch length) I usually use 5/16" plate. | ||
[[File:Keyhole Boiler Inside View.JPG|thumb|center|300px|Keyhole boiler inside view. Photo by Marty Knox.]] | [[File:Keyhole Boiler Inside View.JPG|thumb|center|300px|Keyhole boiler inside view. Photo by Marty Knox.]] |
Revision as of 14:24, 16 August 2013
Copper
- How much stronger is Type K over type L copper tubing? Only 0.009" difference in the wall.
- Let's assume for the moment you are looking for a boiler barrel (The barrel is the long'ish, tubular, front part of the boiler). If you run it through the applicable formlae for boiler barrels you will find that Type M is actually sufficiently strong for 100psi steam. But because there are always other forces acting on the boiler, both during and after construction, as Bill has just mentioned, I don't use Type M. All three types meet the basic strength requirements, but the extra rigidity and weight of Types K and L allow me to handle the material a little bit more like a solid and machine and work it with less concern for deformation. My personal preference is Type L for barrels and Type K for flues. I can usually get Type L locally but the Type K for flues almost always has to be ordered.
Steel
- Pipe and HRS plate are NOT the material to build a boiler, unless the pipe is something like oil well casing which has the same specification / inspection requirements as boiler tubing (I worked for an oil company for 10 years and know this from experience). You need to get certified material that is OK for Pressure Vessel application. A36 is a grade that comes to mind -> here are others, but my head is in European / DIN grades and for the life of me cannot remember the ANSI equivalents at this time.
- I prefer to use rod stays (as opposed to girders). It is easier to calculate the stresses, they don't put a bending stress on the side stays, and they allow better circulation.
- Seamless pipe, SA106B, would be my first choice for the shell. Flat plates should be Pressure Vessel Quality, SA516-Gr70 is the most common. Couplings and half couplings should be 3000# forged steel, ASTM A105. Stays and mudrings can be made from SA36.
- 10" pipe is 10 3/4" OD. In a boiler this size (41-inch length) I usually use 5/16" plate.
What not to use
- It's not a good idea to use brass in a boiler, as it can suffer de-zincification (and failure). I expect the pieces you have are made of bronze, not brass. Bronze does not suffer the same fate.