4.1.2 Pumping speed and throughput

The pumping speed $S_0=\frac{dV}{dt}$

(Formula 1-17) is the mean volume flow through the cross section of the inlet port of a vacuum pump. In diagrams the volumetric flow rate or pumping speed is displayed on the Y axis versus the inlet pressure on the X axis. The maximum pumping speed which a pump can achieve due to its geometry is referred to as its rated pumping speed. Determination of the pumping speed is described in basic standard ISO 21360-1: 2012. Pumping speed is indicated in m3 · s-1. The units of m³ · h-1, l · s-1 and l · min-1 are also customary.

The throughput $q_{pV}=S \cdot p=\frac{dV}{dt} \cdot p$

(Formula 1-16) denotes the gas throughput in a vacuum pump as a function of inlet pressure. It is expressed in Pa · m3 · s-1 or hPa · l · s-1 = mbar · l · s-1. In the case of pumping stations that consist of gas-displacement pumps, all pumps connected in series have an identical throughput.