English to Finnish Tech/Engineering Mechanics / Mech Engineering freezer dryer manual

With a manually operated gas ballast valve, the valve is normally set half open, but is fully open when pumping solvents or condensable vapors.

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"The gas ballast valve fitted to the pump prevents deterioration of the pump performance to be resulted from mixing of condensed vapor with the pump oil. The gas ballast valve plays the role of exhausting the condensed vapor outside the pump."