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How to Attain Extremely Low RH/O2 Concentrations:
Vacuum Cycling vs. Purge and Bleed
Vacuum cycling provides the quickest, most economical way to achieve extremely low moisture and oxygen levels inside a glovebox.
Purge-and-bleed displacement relies on a continuous purge of dry process gas (typically, nitrogen or argon) to displace moisture-laded air, which exits through a bleed valve. This process typically requires many hours, consumes a high volume of process gas, and may never achieve very low oxygen concentrations (below 5 ppm) required in many applications.
Vacuum cycling evacuates ambient air – and with it, moisture and oxygen – inside a vacuum chamber or glovebox. When air is removed, you simply backfill the chamber with process gas until the chamber attains neutral pressure. If needed, this process is repeated until oxygen or moisture concentration reaches the desired level. Typically, only a few cycles, requiring only a fraction of the gas and time of a purge-and-bleed protocol, are all that’s needed to reach single-digit oxygen concentrations.
Once set point levels are attained, close off vacuum valves and use a Dual Purge System and appropriate controller (NitroWatch™ for relative humidity, Trace Oxygen Analyzer for O2 concentration) to maintain dry, anaerobic conditions.
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No. 3305-54B, shown with optional metering valves and vacuum gauge
