Vacuum  Evacuation Time
Vacuum pumps  calculate flow rate and required evacuation time.
The evacuation time for a vacuum pump can be calculated as
t = V / q ln(p_{0 }/ p_{1}) (1)
where
t = evacuation time (s)
V = enclosed evacuated volume (m^{3}, cu.ft)
q = volume flow rate capacity of the vacuum pump (m^{3}/s, cu.ft/s)
p_{0} = initialization pressure  normal atmospheric pressure (mbar, mmHg)
p_{1} = end vacuum pressure (mbar, mmHg)
Note! Leakage through sealing's etc. should be compensated by adjusting the volume flow rate of the vacuum pump.
(1) can be simplified to
t = V / q N (2)
where
N = natural log constant for the actual vacuum
N = 1 for vacuum up to 15 in Hg gauge
N = 2 for vacuum up to 22.5 in Hg gauge
N = 3 for vacuum up to 26 in Hg gauge
N = 4 for vacuum up to 28 in Hg gauge
Example  Vacuum Evacuation Time
Evacuation time of 1 m^{3} volume, evacuated to 500 mbar abs  vacuum pump volume flow capacity 0.1 m^{3}/s  can be calculated as:
t = (1 m^{3}) / (0.1 m^{3}/s) ln((1000 mbar) / (500 mbar))
= 6.9 (s)
Evacuation to 100 mbar abs:
t = (1 m^{3}) / (0.1 m^{3}/s) ln((1000 mbar) / (100 mbar))
= 23 (s)
Evacuation to 10 mbar abs:
t = (1 m^{3}) / (0.1 m^{3}/s) ln((1000 mbar) / (10 mbar))
= 46 (s)
Vacuum Evacuation Time Calculator
The calculator below can be used to calculate the vacuum evacuation time.
Estimated Evacuation Time to Reach 500 Micron Vacuum  6 feet pipe
Related Topics

Gases and Compressed Air
Air, LNG, LPG and other common gas properties, pipeline capacities, sizing of relief valves.
Related Documents

Vacuum
Vacuum is defined as air pressure below atmospheric pressure. 
Vacuum  Air Expansion Ratio
Convert vacuum air volume to standard air volume 
Vacuum  Flow Measurement
Measure air volume flow in vacuum. 
Vacuum  Pressure Units Converter
Converting between vacuum units like % vacuum  mm Mercury  psi  torr  micron  kPa. 
Vacuum Pipes  Flow Velocities
Air velocity diagrams for vacuum pipe lines. 
Vacuum Pipes  Pressure Loss vs. Air Flow
Calculate pressure drops in vacuum pipe lines. 
Vacuum Pumps  Exhaust Pipe Capacities
Capacities of vacuum pump exhaust pipes. 
Water  Boiling Points at Vacuum Pressure
Online calculator, figures and tables giving the boiling temperatures of water in varying vacuum, SI and Imperial units.