Brittle Fracture of Layered Vessels
Brittle Fracture of Layered Vessels
(OP)
I have a question regarding the thickness used in MDMT calculations for layered vessels. The minimum design metal temperature is related to wall thickness in the ASME temperature exemption curves. For layered vessels, do you sum the thicknesses or use the thickest layer (usually inside shell) for calculating your MDMT?
TIA.
TIA.





RE: Brittle Fracture of Layered Vessels
I would use the stress and temperature of the weaker material assuming your using two different materials.
desertfox
RE: Brittle Fracture of Layered Vessels
Cheers,
gr2vessels
RE: Brittle Fracture of Layered Vessels
I still don't understand how I am going to lower my MDMT to our site CET by taking credit for the stress ratio at a lower pressure. It almost seems like I'm conservative for using effective thickness, ULW-16, and just assuming the layered vessel acts as monobloc. Ugh.
This analysis is simply a tool for my boss to judge if he wants to acquire a set of layered firebox vessels from the early 60's for use as ambient temperature accumulators.
RE: Brittle Fracture of Layered Vessels
Why are you worried about temperature if there at ambient?
Can you not just calculate the stresses at ambient for a compound cylinder and be done with it?
Sadly I have no ref to ASME so I can't see what your refering to.
regards
desertfox
RE: Brittle Fracture of Layered Vessels
So I have a vessel with a 3.75 inch inner layer surrounded by 12 0.25 inch layers, of higher toughness. I can find the MDMT at 3.75, but I have difficulty in the stress ratio approach since the MAWP requires those other layers. If I use the equivalent thickness, based on toughness of the two materials, the vessel comes out to be 5.22 inch thick. I can work with that if I assume it's monobloc. It just doesn't seem physically correct, unless those layers somehow contribute to brittle fracture.
RE: Brittle Fracture of Layered Vessels
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