Typical Range Performance of Vacuum Producers

A useful summary of the typical equipment used for developing and maintaining process system vacuum is presented in Table 6-1. Also see Birgenheier [33]. The positive displacement type vacuum pumps can handle an overload in capacity and still maintain essentially the same pressure (vacuum), while the ejectors are much more limited in this performance and cannot maintain the vacuum. The liquid ring unit is more like the positive displacement pump, but it does develop increased suction pressure (higher vacuum) when the inlet load is increased at the lower end of the pressure performance curve. The shapes of these performance curves is important in evaluating the system flexibility. See later discussion. 

A simplified alternate to the previously cited procedures is suggested by Gomez [29] for calculating air inleakage, but it is not presented in detail here. 

Typical Capacities and Operating Ranges for Vacuum Equipment 

Type Lowest recommended suction pressure Capacity range, ft3/min 

Ejectors have the following features that make them good choices for continuously producing economical vacuum conditions  

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