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Vacuum Pumping Speed per. ISO 21360-1 Formulas

Fluid Dynamics Vacuum Engineering and Design

Vacuum Pumping Speed per. ISO 21360-1 Formulas

Vacuum pump performance is rated in terms of throughput, pumping speed, and vacuum pressure capability. They are rated for either intermittent or continuous duty. Throughput is the product of volumetric flow rate and pressure. Pumping speed has units of volume/time and is the mean volume flow through the cross section of the inlet port of a vacuum pump. Determination of the pumping speed is described in ISO 21360-1.

Vacuum pump performance curves are plots of pumping speed as a function of inlet pressure. The lowest pressure that can be achieved by a vacuum pump can be calculated using the following calculator and equation:

pmin = p0 e ( -Sefft / V ) ) + Qo / Seff + QD / Seff + QK / Seff


pmin = deepest vacuum achievable,
p0 = initial pressure,
t = time,
Seff = effective pumping speed,
V = evacuation volume,
Qo = Outgassing flow rate,
QD = Diffusion flow rate,
QK = Permeation flow rate



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