Quote:
Originally Posted by Craig Sawyers
... The background is that cycling to liquid nitrogen results in stress relieving. So at least the plausibility argument is that doing the same thing with a valve changes in some way its characteristics, at least audibly.
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Temperature cycling can indeed relieve stress, but it works just as well if the parts are heated and then cooled. It's just a shame that there's no way for the internal metalwork in a valve to be heated up and cooled down a few times.
Oh ... hang on ...
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Seriously though, during the pumpout procedure for almost all valves the metalwork has to be heated much hotter than the normal operating temperature of most of it to get it to release any trapped gases. By the time it leaves the factory it will have experienced much greater temperature excursions than the 200-odd degrees that an LN2 bath will give it.
I know what you mean about 316 stainless though. When I was a graduate student I used to have TEA laser electrodes machined from it and we went through the same process of rough cutting followed by annealing followed by closer working followed by more annealing followed by even closer working etc etc.
Cheers,
GJ