Types and Features of Mechanical Pumps

There are many mechanical pump designs, the most common of which is the rotary pump. It is named for its use of rotating internal parts that collect, compress, and expel gas from a system. Despite the simplicity in concept, there are very interesting mechanisms that pump manufacturers have developed to overcome the problem of mechanical pumps, namely, that they are inherently a slow pump. It is their simplicity, however, that has made them the general workhorse for creating a vacuum all over the world. 

Finally, because the piston does not need to make actual contact with the internal sections of the pump (only contact with the oil is required), there is less wear than with vane pumps. Because the piston pump parts do not make physical contact, they can tolerate larger-sized particulate matter (which may accidentally enter the pump) and are also more forgiving of internal scratches. 

Rotary piston pump studies made by Sadler12 demonstrated that the above attributes of piston pump design helped them outperform vane design pumps both in speed and vacuum achieved (Sadler compared pumps of comparable size). On the other hand, piston pumps had greater vibration. 

Aside from the two types of rotary pumps mentioned, you will often see the terms single-stage and double-stage mentioned in the context of pumps. A two-stage pump (also called a compound pump) simply refers to a mechanical pump that has one or two pumps connected in line together. The exhaust of the first one 

In the starting position, gas is just about to be drawn into the slide shaft. 

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