We have had two failures in the last 8 months on two separate butterfly valves in which the shaft has galled. These are 30" valves in vacuum service and the process fluid freezes at ~ 100C. Heating fluid is flowed through the valve body jacket at 280C to keep the process fluid vaporized. There is a potential to run heating fluid through the butterfly disc as well, but this requires a flexible hose connection which has been deemed unsafe for carrying heating fluid.
The galling occurs in the bearing area of each end of the shaft. The shaft is Nitronic 50 and the bearing is nitrogen hardened 316SS.
I have a couple questions.
First, is there such a thing as nitrogen hardened 316SS? I did not think this was possible.
Second, is there any data for galling resistance between these two steels? I can only find information on Nitronic 60.
Finally, if the product were to freeze in the bearing area, would this aggravate a galling situation?
Please let me know.
The galling occurs in the bearing area of each end of the shaft. The shaft is Nitronic 50 and the bearing is nitrogen hardened 316SS.
I have a couple questions.
First, is there such a thing as nitrogen hardened 316SS? I did not think this was possible.
Second, is there any data for galling resistance between these two steels? I can only find information on Nitronic 60.
Finally, if the product were to freeze in the bearing area, would this aggravate a galling situation?
Please let me know.
