A double-stage vane pump used in a glove box is designed to achieve a higher vacuum level compared to a single-stage pump, making it suitable for maintaining an inert atmosphere (e.g., nitrogen or argon) by removing contaminants like oxygen and moisture. Here’s a breakdown of its key aspects:
How It Works
1. Two-Stage Design:
– The first stage creates a preliminary vacuum (e.g., ~10⁻² mbar).
– The second stage further reduces pressure (down to ~10⁻³ mbar or lower), enhancing purity.
– Vanes rotate in an eccentric chamber, trapping and compressing gas before expulsion.
2. Oil-Sealed vs. Dry:
– Oil-sealed: Offers better ultimate vacuum but requires maintenance (oil changes) and risks contamination.
– Dry (oil-free): Preferred for glove boxes to avoid hydrocarbon contamination; uses self-lubricating materials like carbon vanes.
Applications in Glove Boxes
– Atmosphere Control: Removes trace gases/moisture after initial purging.
– Regeneration: Cleans desiccants (e.g., molecular sieves) by evacuating absorbed contaminants.
– Process Evacuation: Prepares the glove box for refilling with inert gas.
Advantages
– Higher vacuum levels than single-stage pumps.
– Compact and compatible with glove box
stems.
– Dry versions eliminate oil contamination risks.
Considerations
– Maintenance: Dry pumps may have shorter lifespans due to vane wear; oil pumps need regular servicing.
– Speed vs. Ultimate Vacuum: Balance between pumping speed (m³/h) and final pressure requirements.
– Compatibility: Ensure materials resist corrosion from process gases (e.g., solvents).
Example Models
– Edwards nXDS (dry scroll pump, often paired with vane pumps).
– Pfeiffer Duo series (two-stage rotary vane).
– Leybold SOGEVAC (oil-sealed, high-performance).
For glove boxes, dry pumps are typically favored unless ultra-high vacuum (<10⁻³ mbar) is needed, where oil-sealed pumps may be justified with proper filtration.
Would you like recommendations based on specific pressure requirements or glove box size?