Vacuum systems : time to evacuate

Vacuum Systems

1. Introduction

When designing or operating a vacuum system based on ejectors, it is required to estimate the time necessary to bring under vacuum the process vessel connected to the vacuum system.

2. Time to evacuate

Te = 2.3 V / Ca
With :
Te = Time to evacuate a system from atmospheric pressure to design pressure of an ejector (min)
V = System volume, vapor space, (ft3)
Ca = Ejector design rate capacity (lb/h)

The value given by this formula is an approximation.

Source

Rules of Thumbs for Chemical Engineers, Brannan, Gulf, 2005