Two-Stage Rotary Vane Vacuum Pump

What is the Two-Stage Rotary Vane Vacuum Pump?

A two-stage rotary vane vacuum pump reaches about 0.5 to 0.05 mbar and is the workhorse for medium-vacuum laboratory work. It is used for rotary evaporation, drying, filtration and backing high-vacuum pumps.

Overview

The two-stage rotary vane pump has two rotors in series, each with sliding vanes, so the second stage exhausts into the intake of the first and reaches a deeper vacuum than a single stage. Ultimate pressure is typically 0.5 to 0.05 mbar, and pumping speeds range from 30 to 300 liters per minute. A gas ballast valve admits air to purge condensable vapors from the oil, which is essential when pumping solvents. Oil seals the vanes and lubricates the bearings, and a mist filter on the exhaust keeps oil out of the laboratory air. Internal coatings and oil grades are chosen for chemical service where needed. These pumps are common in rotary evaporation, vacuum ovens, gel drying, freeze dryer backing and Schlenk lines, and they require periodic oil changes and vane inspection.

How does it work?

Vacuum pumps remove gas molecules to lower pressure in a sealed volume. Positive-displacement types, including rotary vane, diaphragm, scroll and roots pumps, trap a volume of gas and push it out. Momentum-transfer pumps, including turbomolecular and diffusion pumps, accelerate molecules toward an exhaust that a backing pump removes. Water-ring and ejector pumps use a liquid or a jet to entrain and carry gas away. Performance is described by ultimate or base pressure and by pumping speed, which is measured in liters per second or cubic meters per hour. Real performance also depends on the gas load, on outgassing from chamber walls, and on the conductance of the connecting piping. Vapor handling, corrosion resistance and cleanliness determine which pump suits a given process, and pumps are often combined in stages to cover a wide pressure range.

What are the key features?

• Two rotors in series for 0.5–0.05 mbar ultimate pressure
• Pumping speeds of 30–300 L/min
• Gas ballast for condensable vapors
• Oil mist filter on the exhaust
• Corrosion-resistant options for solvent duty
• Suitable as a backing pump for high-vacuum pumps

What are the technical specifications?

A typical two-stage rotary vane vacuum pump configuration offers ultimate pressure of 0.5–0.05 mbar, pumping speed of 30–300 L/min, number of stages of 2, motor power of 0.25–1.5 kW, oil capacity of 0.3–1.5 L and gas ballast of Yes. Values are indicative of the product class; the exact figures for each configuration are confirmed on the quotation and the calibration documents supplied with the instrument.

Which applications is it used for?

The Two-Stage Rotary Vane Vacuum Pump is used in rotary evaporation, vacuum oven and drying, freeze dryer backing, schlenk line vacuum and filtration under medium vacuum. Across the wider Vacuum Pumps class, laboratories also deploy it for chamber evacuation for drying and degassing, rotary evaporation and distillation and freeze drying and centrifugal concentration.

Which standards and certifications apply?

Relevant standards and methods include IEC 61010-1, IEC 61326-1, ISO 21360, ISO 27893, ISO 20485 and GB 4793.1. Certification candidates for this model are CE, RoHS and ISO 9001 manufacturing; each is to be confirmed for the specific configuration before shipment, and certificates are supplied only where they have been issued.

Protect the pump from the process with a cold trap, foreline trap or filter, and vent to atmosphere before switching off a high-vacuum pump. Change oil and check seals on schedule for oil-sealed pumps, and inspect scroll tips and diaphragms for dry pumps. Keep tubing as short and wide as possible to preserve conductance, and use the correct flange type and vacuum grease sparingly. Monitor pressure with gauges appropriate to the range, such as Pirani, capacitance or ion gauges. Follow IEC 61010-1 for electrical safety and local pressure equipment rules. For oil-free or clean processes, confirm that the pump cannot backstream oil or particles. Record base pressure and pump-down curves during commissioning and at each service so that degradation is detected early.

How do I select the right Two-Stage Rotary Vane Vacuum Pump?

Choose a two-stage rotary vane pump for medium vacuum with low cost and proven reliability, adding a trap and mist filter for solvent work. For oil-free cleanliness, choose a scroll pump. In the RFQ, state ultimate pressure, pumping speed, solvent exposure and connection size.

How does it compare with other Vacuum Pumps variants?

Work from the required working pressure, the gas composition and the volume to be evacuated. For rough vacuum in filtration and drying, a diaphragm or single-stage rotary vane pump is sufficient. For medium vacuum in rotary evaporation and coating, a two-stage rotary vane or scroll pump is appropriate. For high and ultra-high vacuum in electron optics, surface analysis and semiconductor work, a turbomolecular pump with a suitable backing pump is needed. Consider whether the gas is condensable, corrosive or particle-laden, and add traps, filters and corrosion-resistant materials as required. Size pumping speed from the chamber volume, the target pressure and the acceptable pump-down time, remembering that conductance limits real speed. Decide between oil-sealed and dry designs based on contamination risk, and specify gauges, valves and controllers as part of the system.