Molybdenum pressure vessel
Molybdenum pressure vessel
(OP)
Hi,
I am designing a pressure vessel out of pure moly. It should hold 1 atm of nitrogen and will be heated to 1500C. The max. diameter is 600mm and it will be about 1m long. I am concerned about sealing the vessel (i.e. what metal to use as a seal) and constructing valves ( since welding moly. is very difficult). Does anyone have any experience with these conditions or working with moly.? Thanks
I am designing a pressure vessel out of pure moly. It should hold 1 atm of nitrogen and will be heated to 1500C. The max. diameter is 600mm and it will be about 1m long. I am concerned about sealing the vessel (i.e. what metal to use as a seal) and constructing valves ( since welding moly. is very difficult). Does anyone have any experience with these conditions or working with moly.? Thanks





RE: Molybdenum pressure vessel
RE: Molybdenum pressure vessel
What property of this metal appeals to you ?
Explain why you cannot use a high grade of stainless steel in this application
There is an expensive alloy called TZM that is ~99% Molybdenum,... used in high-temperature molten salt reactors
Moly, of course, is an important alloying element for may grades of stainless steel.
MJCronin
Sr. Process Engineer
RE: Molybdenum pressure vessel
@MJCronin I don't believe anyone has done this before. I need to use moly. because of the high temperatures and nitrogen atmosphere, stainless steel will not work for these temperatures.
RE: Molybdenum pressure vessel
Regarding Molybdenum, like many metals, the pure form is not always your best choice where strength at temperature is your desired property.
See the following:
http://www.lr.tudelft.nl/organisatie/afdelingen/sp...
http://www.fusion.ucla.edu/apex/meeting4/2ghoniem0...
Consider rocket motor INCONEL 718 as an alternative.
Consider the alloy TZM at 1500C, It seems that it was developed for high temperature service..
Respect us..... tell of your final decision and the reasons for your choice
MJCronin
Sr. Process Engineer
RE: Molybdenum pressure vessel
I would hope your pressure vessel is exempt from local regulations within the US where pressure vessels are regulated. If it is not exempt, you will be in violation of the law unless you follow ASME B&PV code rules.
Do you have Boiler and Machinery insurance? You may want to consider this when you build this pressure vessel. Do you know and understand pressure vessel theory?
RE: Molybdenum pressure vessel
@MJCronin It's between TZM and moly. The other materials just aren't as strong at high temperatures and I'm afraid of this thing blowing up like a balloon. If the design works it won't be built for at least another year but I'll let you know what happens with it. Thanks for you help.
RE: Molybdenum pressure vessel
RE: Molybdenum pressure vessel
RE: Molybdenum pressure vessel
I truly hope you understand mechanical design theory better than I understand Chemistry.
RE: Molybdenum pressure vessel
there are a couple of books you should look at, that will have a wealth of high temperature operating strength data for refractory alloys:
https://books.google.com/books?id=yl9kAAAAMAAJ&...
http://link.springer.com/chapter/10.1007%2F978-1-4...
RE: Molybdenum pressure vessel
Use TZM or one of the other Mo alloys.
Have the half spheres spun formed, when weld them together in a vacuum chamber.
You may need to use ceramic for the valve, not too many options.
The ceramic could be metallized and them diffusion bonded to the Mo.
A lot of R&D work to build this.
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P.E. Metallurgy, Plymouth Tube
RE: Molybdenum pressure vessel
@EdStainless I need to fit another cylindrical chamber inside this pressure vessel so a sphere would not work.I'll look into ceramic valves, thank you!
RE: Molybdenum pressure vessel
Could you help me to understand how the state of stress in a hemispherical vessel is less than that of a cylindrical shell when designed for a pressure of 0 psig?
RE: Molybdenum pressure vessel
Not too many ceramics are brittle at 1500 C- and after first heat up, your moly will be brittle below 300 C too. So what does using metal really gain you?
RE: Molybdenum pressure vessel
RE: Molybdenum pressure vessel
As long as welding is not required, a FeCrAl alloy (Kanthal etc.) might be worth considering.
RE: Molybdenum pressure vessel
Never any positive pressure?
Why not graphite? they make vacuum furnace liners and elements out of it.
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P.E. Metallurgy, Plymouth Tube