I was thinking agout the material Old F brought up, the 160. I tried to identify it and could not find that exact grade. closest thing to that I could find was N 155. I figure this must be some type of inconel alloy 600. And if im not mistaken this is a material that retains its tensile strength at very high temps. My uncle uses a simular material for the propane heat exchanger on his ballon burner. That is a super-alloy, its really amazing stuff, it can be red-hot and still holds its strength.
I want to add something here that will give others an idea of the kind of things, that you should educate yourself on, should you become involved with a steam project. I have done this on every-single-peice thats in my system. there is a formula called "Barlow's Formula" its what you use to determine what your componets bursting pressure is. "P=2St/D"
where P = bursting pressure in psi
S = tensile strength of tube material
t = Wall thickness in inches
D = outside diameter in inches
here's an example-
to find bursting pressure of a tube with a 4" OD X .250 wall, with tensile strength of 80,000 psi:
2 X 80,000 X .250 40,000
P= ------------------- = -------- = 10,000 psi bursting pressure
4 4
the formula may be rearranged to determine necessary dimensions or tensile strength to produce a desired bursting pressure, as follows:
DP 2St DP
t = ---- D = ----- s = ----
2S P 2t
examples:
to find the wall thickness nessiary to withstand a pressure of 10,000 in a 4" OD tube with 80,000 psi tensile strength:
4x 10,000 40,000
t = ------------ = -------- = .250 wal thickness
2 x 80,000 160,000
to find necessary OD to withstand a pressure of 10,000 psi in a tube with .250" and a tensile strength of 80,000 psi:
2 x 80,000 x .250" 40,000
D = --------------------- = ----------- = 4" outside diameter
10,000 10,000
to find the tensile strength of material necessary to withstand a pressure of 10,000 in a tube 4" OD x .250" wall:
4 x 10,000 40,000
S = ------------- = ---------- = 80,000 psi tensile strength
2 x .250 .500
2 St
Again the formula is P = -------
D
tensile strength is very important, material analysis will give you this information for example 316L , which is the material I use, has a tensile strength of "minumum" 75,000 psi.
Working pressures are generally 1/4 of the bursting pressure from barlow's formula. so if it busts at 10,000 psi safe working limit should be 2,500 psi.
temperature compensation should also be alocated for as well, generally if the material is 'hot" it losses tensile strength. for example 316L losses 15% of its tensile strength at 600*f.
Interesing note here the 160 material Old F brought up does not lose as much strength at the same temp. 600*f
Old F I was thinking about i fred's website sorry. got you two mixed up there for a second sorry.
-JW