Higher Flow Rates for Higher Productivity

The “flow rate” (air displacement) specification of a vacuum pump represents its peak ability to move vapor when the pump is generating little or no vacuum. The actual flow rate steadily decreases to zero as the pump reaches its design “ultimate vacuum.” A well-designed pump retains more flow rate throughout its working range, then drops off sharply close to the ultimate vacuum. Less powerful pumps sacrifice flow rate rapidly as vacuum builds in the application.

At every point in between the flow rate specification and the zero flow rate at the pump’s ultimate vacuum, the pump has a flow rate capacity that can be measured. To present several orders of magnitude of vacuum data concisely, it is often charted as a “flow curve” on a log-log scale.

Pumps with the same ultimate vacuum and specified ”flow rate” often differ dramatically in their ”work rate,” that is, their flow rate at working vacuum levels*. Here, the performances of two hypothetical pumps are plotted on a flow curve. Both pumps depicted have identical ultimate vacuum (~10 mbar) and flow rates at atmospheric pressure (~1.8 cfm), but different work rates during use.

Why is this important? Selecting a pump with a higher workrate can greatly reduce process times. For example, if you were using vacuum to evaporate water at 20°C (vapor pressure 23mbar), the pump represented by the red curve would evaporate it twice as quickly as the pump represented by the blue curve, despite their identical specifications. This greatly improves process productivity, saving you time on every application.