The single-stage, lubricated rotary vane pump comes with an integral and closed-loop oil-circulation system. Though the construction is compact, it is a heavy-duty vacuum pump.
These vacuum pumps use the rotating vane assembly in the pumping chamber to move the gas or fluid mediums, creating areas of low pressure. This feature makes the rotary vane vacuum pumps workable for the low-pressure application requiring small or medium vacuum ranges.
Understanding the Working of Rotary Vane Pump
These vacuum pumps operate on the principles of positive rotary displacement. The system includes a housing, rotor, vanes, along with an inlet and outlet valve.
When the rotor starts turning, the vane ends hardly touch the housing. This process creates a seal from inlet to outlet. The inlet and outlet are usually perpendicular in position. The working chamber divides into two individual spaces with variable volumes, owing to the rotor and vanes.
As the rotor turns, the gas continues to flow into the large suction chamber, until it gets sealed off by the next vane. It results in an increased cell volume on the inlet port side, thus creating a vacuum. This enclosed gas gets compressed until the outlet opens against atmospheric pressure.
Listed below are some essential specifications of these vacuum pumps, making them suitable for low-pressure applications.
Maximum Achievable Operating Vacuum
The ultimate operating vacuum is the lowest possible pressure these pumps can generate within a stipulated timeline. You must understand the conditions and assumptions made by the manufactures to achieve these values.
The manufacturers, at times, make unrealistic assumptions like ignoring the pressure from condensable gases like water vapor.
The pumping rate or vacuum flow is the volumetric rate at which the gas gets emptied from the vacuum chamber. These pumps come with pumping speed ranging between 0-5, 6-12, and 13-21 m3/h. This rated pumping speed is the pump’s maximum attainable pumping speed, over its entire pressure range.
Pumping speed must match as per the needs of the low-pressure application, which is dependent on the pump’s chamber volume, desorption, and process gas volume.
The rotary vane vacuum pumps get powered by an electric source, usually alternating current (AC) and, at times, direct current (DC).
AC power is a more standard power source for these pumps. The single-phase AC motors are generally cheaper compared to the three-phase AC motors. However, they are relatively less efficient. On the contrary, DC power sources make use of DC power from the battery.
Role of Gas Ballast
The gas pumped out of the vacuum system gets contaminated with water vapor, solvents, alcohols, and other condensable gases. These gases cause condensation inside the chamber housing before they get exhausted. This process contaminates pump fluids. The contamination increases gradually, adversely affecting the performance of the pump. The pump then, cannot attain the ultimate pressure required for low-pressure applications.
It is where the gas ballast valve comes into use. It lets the ballast air enter the compression chamber. This air forces out the contaminants from the chamber before they condense.
These rotary vane pumps are practical and versatile, with good airflow. These are robust and cost-effective pumps suitable for low-pressure applications.