On June 28, Blower & Vacuum Best Practices hosted a webinar on how to maximize benefits of Variable Speed Drive (VSD) vacuum pumps. Industry experts including Compression Engineering Corporation’s Tim Dugan shared valuable tips on the fundamentals of vacuum, determining vacuum and flow requirements, and sizing vacuum pumps. Following Tim’s presentation, I reviewed the importance of considering both the vacuum pump and the process in order to maximize benefits and savings.
There’s a common misconception that allowing pumps to run at ultimate vacuum means that users will have the lowest power consumption, but that’s simply not the case. In this scenario, the user is simply considering the pump alone and not thinking about the actual process. If the pump runs continuously and achieves the manufacturer’s published ultimate vacuum level, it’s likely that the pump is oversized and wasting energy.
Power consumption: fixed speed compressor vs. fixed speed vacuum pump
If you take a fixed speed compressor you’ll see that its power level matches demand at full load, which is also true for a fixed speed vacuum. The difference occurs during unload situations. When demand goes away, a fixed speed compressor’s power drops back to 25 percent of full load power. For a vacuum pump at ultimate vacuum with virtually no flow, it still consumes roughly 60 percent of its loaded power.
VSD vs. fixed speed system pressure
Vacuum processes are never constant and the demand varies. It’s important to achieve a stable pressure to meet the varied demand. With a fixed speed pump, the machine cannot adjust its rotor speed so the process demand increases while the system pressure increases. On the other hand, with a VSD pump, the technology adjusts the rotor speed to match demand coming from the process and maintains a constant pressure. With process demand increasing, the VSD machine accelerates and as the demand decreases, the machine slows down.
To learn more about VSD technology and ways to optimize vacuum pumps for VSD control, visit Blower & Vacuum Best Practices to access the full webinar.