Inlet Nozzle - Steam Centrifugal Compressor

[awhicker84]

Hi,

I'm trying to figure out the best materials for an inlet nozzle on a steam machine. The steam is superheated, but inevitably some liquid condensates.

The current solution is cast iron with a nickel coating. I see other steam machines using 316L, but I'm having a hard time finding repair history. (The impellers are 17-4PH) 17-4PH has a much harder surface than 316L. If we are using stainless to remove corrosion effects, but also trying to pick a material that will slow down water drop erosion, would 17-4PH be the best solution?

Cheers and thanks,

 

[metengr]

What is the superheated steam temperature and pressure on your steam machine? You need to know this before one could consider a materials recommendation. The 17-4 impeller is exposed to direct impact with flow and centrifugal forces, which requires increased strength. I have seen carbon and low alloy steel cast, fabricated or forged centrifugal compressor casings with a corrosion resistant overlay (CRA) depending on the contents/quality of the steam.

 

[EdStainless]

The 316 is very corrosion resistant, has good high temp resistance, and the surface will work harden under droplet impingement. If you need better performance a Ni alloy such as 625 or the Co based Ultimet would be logical options.
I am not sure that 1704PH would offer any advantage.

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P.E. Metallurgy, Plymouth Tube