Gear Pumps

Gear pumps are positive displacement rotary pumps used to transport high pressure and high volume flows.  They function through the use of two or more internal gears that create vacuum pressure, propelling the fluid media. Typically a rotating assembly includes a driving gear and a driven gear.  As each tooth of the gear makes contact, the load moves to the next tooth and fluid moves with each contact.  Internal gear pumps or “gear within a gear” pumps may have their smaller gear turning in the same direction as the larger gear, creating suction to move the pumped fluid media.  At various points during the process of turning, the gears create a seal between the inlet and outlet sides of the rotation assembly chamber or body. 

Gear pumps provide a comparably continuous, non-pulsating flow in relation to diaphragm pumps or peristaltic pumps.  For this reason, gear pumps may be preferred in a number of applications from laboratory to petrochemical and marine applications, and processes involving hydraulic presses and dry pit steam power.  Gear pumps are reliable when using media with heavier viscosities, however, build up or interference within the internal mechanisms may cause the gears to rotate more slowly.  The addition of a pressure relief valve to the system may help to alleviate some of this slow down, and provide a longer life cycle as well.

As in other mechanical applications, the speed ratio of the rotating assembly in gear pumps is dependent upon the size of the gears, the number of teeth in the gears, and the pitch.  The type of gears can alter the rotational speed of the gears; however, the flow rate is independent of the gear ratio. The flow rates may range from 3 ml/min to 10000 GPM. 

Gear pumps are available with a number of features that help sustain their service life cycle and enhance overall performance.  Some models are designed to “run dry,” meaning that if the supply of fluid media is cut off, they will still function.  Gear pumps without this ability may breakdown if the media flow stops; come as catastrophically as an engine forced to run without oil.  Other important features include ratings for continuous duty, where the pump can be left on with little fear of malfunction or overheating; and self-priming abilities, which also enhance the functional life cycle. These options are not available on all models, so knowledge of the applications in which a given pump will be used, and the rigors it will face should help to determine which are needed.