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Using distilled water and regular flushing should keep it pretty rust-free Thomas. It's 316 stainless, right? Since it only gets pressure once in a while (not continuously) it should last a long while.[/quoteHi Bent,No the material is ASTM A500b steel so it will need some kind of protection. I have ordered some chemicals that the model steam locomotive folks use in their boilers and will actually "coat" the interior. I do plan to completely drain it when not in use for any long period of time. Have a great day,Thomas
4 to 1 factor of safety is appropriate. That said the working pressure should be 15 psig. Per your calculations.That is a parameter that is set when the boiler is built, and then verified with a hydrostatic check to no more than 2x working pressure after completion.Now is not the time to raise the working pressure. Dave
If it is the type of water treatment we use over here then you don't actually apply a coating to the inside of the boiler. You add it to the water and it will leave a deposit on the inside surfaces as the boiler is used, they are usually tanin based and exclude oxygenDave beat me to the other bit, I'd also add that the three calculations you showed all had diameter as part of the calculation which you used the ID of your pipe as the figure used. A round pipe will have a lot more inbuilt strength than a flat sided (square) pipe. You should really be using the calcs for fireboxes or tubeplateswhich are flat.
The formulas that I used are for non-cylindrical vessels, ie. flat side, not pipe or tube.Thomas
Quote from: Ye-Ole Steam Dude on October 24, 2017, 12:45:54 PMThe formulas that I used are for non-cylindrical vessels, ie. flat side, not pipe or tube.ThomasThe three formulas you posted all have "D" in them for ID of tube so don't know how you can say they are for flat surfaces and not tube?I just ran some sizes through a spreadsheet that is used by a commercial model boiler maker here in the UKWith 3/16" wall a round seamless pipe would be good for 783psiIgnoring wall thickness the bottom of your boiler on the large side of the Z shaped baffle will be 6" x 9" that just about squeezes in at 15psi MAX WORKING PRESSURE see 6x61 belowNow if you were to run one stay from side to side and end to end of each of the 9 opposed faces you could get the boiler so it would work to the pressures you are now talking about see 6x62 below