Diaphragm vacuum pump

 The Design , Operating principle of Diaphragm vacuum pumps:

Diaphragm vacuum pumps are dry positive-displacement pumps, their operating principle is explained as in Figure. A crankshaft-driven connecting rod-3  moves the diaphragm-2 that is tensioned between head cover-5 along with compressor housing-4. The space between the head cover-5 along with the diaphragm-2 forms the suction chamber-6. Diaphragm pumps require inlet valves and outlet valves (check valves-1) to achieve aligned gas displacement. Pressure-controlled shutter valves made of elastomer materials are used as valves. Because the suction chamber is hermetically sealed off from the drive by the diaphragm, the pump medium can neither be contaminated by oil nor can aggressive media corrode the mechanics. The harmful space between the outlet valve and the suction chamber results in only a limited compression ratio. This means that an ultimate pressure of only approximately 70 mbar can be attained with a single pump stage. Connecting multiple pumping stages in series can reduce ultimate pressure to 0.5 mbar. Lower pressures cannot be achieved, as in this case there is no longer sufficient force to open the inlet valve. The principle of the diaphragm pump is particularly well suited for low pumping speeds of up to approximately 10 m3/ h.
If compared to rotary vane vacuum pump is Diaphragm pumps don't achieve as low vacuums as Rotary Vane pumps. But are a popular choice for everyday use with filtrations, desiccators and for aspiration of waste liquid in microbiology. Larger diaphragm pumps are also available to use with rotary evaporators or vacuum ovens.