Material for high pressure hot oxygen gas

[Suresh babu]

Friends, I am new to this site. I found this site very useful for engineering issues. I have one material related problem. I need to chose suitable material for oxygen transportation at 120 bar and 700 kelvin temperature. Based on some literature, I found inconel and monel. Gas velocity will be a factor? Somewhere I read pv factor. Pressure multiplied by velocity. Inconel 718 has high pv factor compared to monel 400. Another reference tells monel 400 has higher exempt pressure than inconel 718.also, some references tell minimum material thickness. I need to design a convoluted hose for flexibility requirement. That means I can have thickness of the order of 0.4 mm for making convolution. Is there anybody who can help to select suitable material for my application.
Thanks in advance.

 

[EdStainless]

Flexible hose at 120bar/700K? Sounds like a stretch. Do you really need hose or are you just making up for thermal expansion?
There are publications from NASA that address metals use in pure oxygen and the ignition risks.
I would start with those (I have them in hard copy but not electronic).


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[MGZmechanical]

You can try at Eiga site:

https://www.eiga.eu/publications/catalogue-of-publications/

With oxygen service you have pressure, temperature, velocity, degreasing of materials,...

Regards

 

[Suresh babu]

Thanks for your quick reply.
My application is to connect an inlet line to swivellable thruster. Hence, flexibility is a must. Thruster swivels by around 50 degrees. I have to supply hot oxygen to that. I gave gone through one of the eiga publications applicable for ground oxygen systems. There, they are not recommending flexible connections for oxygen lines.

 

[btrueblood]

The space shuttle used bellows joints (and they were Inco 718 if memory serves, it's been 30 years since I worked on it) on the main engines, but these carried LOX not hot oxygen. Also, the swivel angle was less than 10 degrees max. So, you are breaking new ground I fear...tread carefully.

Ground oxygen piping rules will only take you so far, rocket science is a different matter. In piping manuals, monel gets a better rating because its high copper content makes it more thermally conductive, and thus less likely to ignite from abrasion/impact events. But its strength-to-weight ratio is a lot less than inconels in general, and worsens at higher temperatures.

 

[IRstuff]

Is oxidation an issue? Inconel appears to oxidize at higher temperatures:

https://link.springer.com/article/10.1023/A:1010359815550,

Monel, possibly:

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19740017913.pdf

TTFN (ta ta for now)
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[racookpe1978]

"swivel 50 degrees" is +/- 25 about the centerline? Wow.

I doubt even a "spring coil" pipe (looped once or even twice), would be flexible enough in a small enough space.

 

[Suresh babu]

Where can I get temperature dependent properties for materials like monel, inconel etc. Is there any reliable database online?
I am thinking of flexible hose made of monel. Is there any minimum thickness constraint for monel for hot oxygen.

 

[moltenmetal]

Pressure piping codes such as ASME B31.3 list both inconel 600 and monel 400 as pressure bearing materials and give safe allowable stresses for them versus temperature. But there's more to it than that in designing a flex hose...

The risk with oxygen is METAL COMBUSTION, not merely oxidation. You can turn your component into a cutting torch.

 

[mdm55]

To expand on moltenmetal's comment, most heat resistant alloys rely on an oxide film that is relatively brittle. Flexing of the convoluted hose will tend to disturb the oxide film, which will result in exposure and re-oxidation of the underlying metal. You might be able to avoid a conflagration, but accelerated surface oxidation will have an impact on service lifetime.