A liquid ring vacuum pump (LRVP) uses an eccentric impeller rotating in a cylindrical casing partially filled with service liquid (typically water). The liquid ring forms a seal and creates expanding and contracting volumes that draw gas in at the suction port and discharge it at a higher pressure — typically atmospheric or into a separator vessel.
Operating Range
| Parameter | Typical Range |
|---|---|
| Suction pressure | 30–500 mbar absolute (deeper vacuum requires two-stage LRVP) |
| Capacity | 50 to 50,000+ m³/hr air equivalent |
| Suction gas temperature | Limited by service liquid temperature — typically < 80°C |
| Power consumption | 5–50 kW per 100 m³/hr depending on vacuum level |
| Seal water consumption | 0.5–2 l/min per m³/hr capacity (recirculated in closed loop) |
Service Liquid Selection
- Water: Standard for most applications. Seal water temperature directly affects achievable vacuum — warmer water = higher suction pressure (worse vacuum). Keep seal water below 15°C for deep vacuum.
- Oil (sealed LRVP): Used when water contact with process gas is unacceptable. Common in pharmaceutical and food vacuum applications.
- Solvent-compatible liquid: When process gas dissolves in water, use a service liquid compatible with the process (e.g., glycol, process solvent).
LRVP vs Steam Jet Ejector — Decision Matrix
- Choose LRVP when: electricity is cheaper than steam, suction pressure is above ~30 mbar abs, cooling water for ejector intercondensers is limited, or the gas load is relatively constant.
- Choose steam ejector when: deep vacuum (< 10 mbar) is required, suction gas contains corrosive or high-temperature vapours, steam is available as waste heat, or gas load varies widely.
- Hybrid systems: Steam ejector first stage + LRVP as backing pump — common for 5–50 mbar applications in chemical plants.
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