Diaphragm pumps belong to the group of dry transport pumps. They are used mainly in analytical and R&D applications, where high pumping speed is not important, but good vacuum cleanliness is required. In these cases it usually serves as the primary pump for Holweck stages turbomolocullar pump systems.
The principle of the operation is based on and oscillating flexible diaphragm stretched in a closed pumping chamber equipped with an intake and exhaust valves. This chamber then forms one stage of the pump. Depending on the number, size and arrangement of the individual stages the diaphragm pumps reach a pumping speed of 10 to 160l/min. - 1 and a limit pressure up to 0.5 mbar.
In principle, this type of pump has a limited possibility of pumping water vapor. The possibility of using gas-ballast valves in some types partially eliminates this feature.
Pumps with coated membranes and hausing with increased corrosion resistance are designed for pumping corrosive gases. These types are marked with the letter C.