Vacuubrand. One of the most common questions we hear from our customers is: What pump do I need? The right answer depends upon a variety of factors, such as the nature of the process or application, the working pressure and/or flow rate required, the desired process time, if the pump will be exposed to aggressive chemicals, and what sort of process control is desired (manual, electronic, automated). This paper addresses each of these issues, in turn. Step one in specifying a pump is to define how much vacuum you need. “Vacuum” in applied work simply means pressure below atmospheric pressure, so how much below atmospheric pressure is the key question, and determined by your process. Once you know the depth of vacuum needed, this will determine your technology options. Some technologies – such as diaphragm pumps – can support operations down to about 2 mbar, or about 0.2% of atmospheric pressure.