spots on metal surface after applying pressure

[jangolobow]

Hallo

I have question. From raw material supplier we obtain material in desired form (cast). We assemble this part and clean it (with first hot water and after with dry ice and again in hot water). Material surface is completely clean. After applying pressure on this part some spots appear on the material surface. We did analyses of those spots and they are from carbohydrates. Does somebody have idea why those spots would appear and from where do the arise? Prior we apply pressure there is no spot after we apply pressure spot appear. Is it possible that there are some impurities “hidden” in material? And after applying pressure they diffuse out from valve body? Applied pressure is up to 600 bar, surrounding temperature (up to 30degC)? We apply pressure by water 8it is clean – spots can not appear from test fluid)!

 

More info needed, starting with the material.

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[IRstuff]

OK, so can you detect carbohydrates on the surfaces prior to pressurization? If not, then the pressurization process is adding them, no? Or, an alternative is that the water is leeching carbon from the valve material itself; have you analyzed the material for carbon?

Have you analyzed the water itself; pressurization implies pumps, which imply lubricants, which are often carbon-based, i.e., oils.

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[EdStainless]

Dry ice is a good source C as well and can from many compounds. Perhaps your final wash isn't as thorough as needed.

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