I am considering to use alloy 602CA for the retort of a batch type hydrogen brazing furnace. The furnace has a double walled retort. The interspace is evacuated and the sealing is through the bottom flange. The interspace serves as a barrier of hydrogen leakage towards the Kanthal heating elements. The interspace will be continuously evacuated by a rotary pump to monitor the hydrogen concentration which may show up when there is a a leak from the inner retort. This way, we can obtain an explosion proof design. But the external vessel of double walled retort needs design against buckling at 1100 deg C. How can we get the properties / external pressure chart applicable to 1100 deg C?
Article Case Histories of Successful Applications of Alloy 602CA, UN...
I would not expect hydrogen diffusion through the wall to be an issue. I see more problems with your design (greatly reduced heat transfer) than it solves. Normally just nitrogen purging the space between the retort and heating elements is considered sufficient to be safe.
Your temperature is not extremely high, 602CA and other HT alloys will work well in this range. I have hydrogen annealed in retorts made of alloy X, 600, 242, cast HK and HX, and pure iron. It all depends on configuration and mechanics.
Thanks Ed for your informative reply. The maximum temperature of the retort can go up to 1100 deg C; therefore I thought 602CA to be the material. Nitrogen purging between the heating elements and single wall retort appears to be a better solution. We can put some hydrogen sensor in this space to find out if hydrogen is leaking from the retort to initiate corrective action. Can you suggest me how to seal the retort if the bottom flange is not actively cooled?
I want to add Ed that I am not concerned about permeation through 602 CA walls but a leakage through the welds or the seal.
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