Efficiency Comparison for Vacuum Pumps

Efficiency Comparison for Vacuum Pumps

Which vacuum pump achieves the higher efficiency factor? When tested under realistic conditions, the result is very clear: In a direct comparison with an oil-lubricated screw vacuum pump, the R 5 from Busch proves to be far superior.

Background: Apples vs. oranges

A compressor manufacturer that was also attempting to apply its technology to vacuum generation initiated a trial. During the test, it compared its oil-lubricated screw vacuum pump (SVP) with an oil-lubricated rotary vane vacuum pump (RVVP) from Busch. During the test cycle, both vacuum pumps also continued to run during long breaks in production. The frequency-controlled SVP's rotational speed dropped while idling, meaning that its power consumption also dropped.

However, this scenario (leaving the vacuum pump running while the rest of the machinery is idle) barely ever occurs in actual industrial settings. Furthermore, it is like comparing apples with oranges, as the RVVP was operated without a frequency converter.

Realistic testing conditions

The independent German testing organization TÜV Süd then conducted a comparison test using the same vacuum pumps under realistic conditions. The RVVP was fitted with a built-in frequency converter. The test simulated the typical working cycle of a packaging machine – one of the most common applications for industrial vacuum technology.

The results of the tests were clear: The rotary vane vacuum pump evacuates faster and consumes less energy than the screw vacuum pump. In terms of specific energy consumption (SEC), the RVVP was superior to the SVP at all levels. The differences ranged between 13% and 73%. At the level of 10 mbar (typical in practice), the RVVP consumes 38% less energy than the SVP.

Vanes significantly better

The RVVP uses classic vacuum pump technology, while the SVP is essentially a converted compressor, which generally runs at a high rotational speed. At full load, the speed is around 7,000 rpm, while the RVVP has a maximum speed of 1,000 rpm. The lower rotational speed during operation generally facilitates lower power consumption, while also reducing the mechanical load and, as a result, maintenance requirements.

The less residual gas there is to be conveyed, the more economical the rotary vane vacuum pump becomes. Its performance remains constant, from the start to the end of evacuation. In contrast, the SVP requires separate pressure control to prevent overloading. Until the rough vacuum is reached, its output is lower, which is why it also takes a lot longer to evacuate.

Our overview summarizes the most important aspects of the efficiency comparison.

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