Speaking the Same Industrial Language: Vacuum Terms for the Compressor Expert

If you work with compressors, you probably know a lot about the terminology that goes with them. What about vacuum pumps? At first, it may seem like they are just the opposite of air compressors, removing air molecules from a space rather than compacting them. And they do — but this technology comes with an entirely different set of terms and measurements. Today on Speaking the Same Industrial Language, we’ll take a look at some common vacuum terms and put them in context for compressed air experts.

Flow measurement

Unlike compressed air flow, vacuum performance is not expressed in power (horsepower or kW), but in volumetric flow rate (cfm or m³/hr). And not just any flow; vacuum measures in actual cubic feet per minute (ACFM). This means the flow is measured at the actual conditions at the inlet of the pump; in other words, at the conditions in which the customer operates.

This is another departure from compressed air flow measurements, which are typically assessed in standard cubic feet per minute (SCFM) or free air deliver (FAD). Volumetric flow measured at the standard conditions assume a pressure of 14.7 PSIA and temperature 68°F, regardless of actual conditions.

Performance

Ultimate pressure is the best vacuum that the pump can achieve. At this point, the machine delivers zero net flow. A perfect vacuum means there are zero molecules in a space. This is theoretical, as no one has achieved it; outer space is the best example of a perfect vacuum.

Levels of vacuum are divided into four main categories: rough, medium, high and ultrahigh. Ultrahigh vacuums come the closest to achieving a perfect vacuum and are used in particle accelerators, atomic physics, surface analytic techniques and other scientific research.

Gauge and absolute pressure

There are two ways to measure vacuum pressure: gauge pressure and absolute pressure. Gauge pressure is dependent on barometric pressure, and when a vacuum is vented, the pressure gauge should point to zero. On the other hand, absolute pressure is independent of local pressure, making it a more accurate reading. When a vacuum measured in absolute pressure is vented, the gauge will point to atmospheric pressure.

So there you have it — a vacuum terminology introduction for compressed air experts. What industrial terms do you want to know more about? Let us know in the comments below!