Fluid Flow Control Easy Source

Easy Source Fluid Flow Control - Gear Pump

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Gear Pump
Gear Pump
Gear Pump Gear Pump - External type gear pumps most often designed for generating flow in lubricous liquids, regularly found in fluid power hydraulic circuits. The concept involves generating oil flow by two gears meshing together in a relatively tight enclosure. Size of the gears & tightness of enclosure determine what the pump is capable of generating. "Internal gear" tend to be for lower rpm applications with higher viscosity liquids.

Wikipedia Gear Pump

Gear pumps use the meshing of gears to pump fluid by displacement. They are one of the most common types of pumps for hydraulic fluid power applications. There are two main variations; external gear pumps which use two external spur gears, and internal gear pumps which use an external and an internal spur gear. Gear pumps are fixed displacement, meaning they pump a constant amount of fluid for each revolution. Some gear pumps are designed to function as either a motor or pump.
As the gears rotate they separate on the intake side of the pump, creating a void and suction which is filled by fluid. The fluid is carried by the gears to the discharge side of the pump, where the meshing of the gears displace the fluid. The mechanical clearances are small—on the order of a thousandth of an inch (micrometres). The tight clearances, along with the speed of rotation, effectively prevent the fluid from leaking backwards.

The rigid design of the gears and housing allow for very high pressures and the ability to pump highly viscous fluids.
Many variations exist, including; helical and herringbone gear sets (instead of spur gears), lobe shaped rotors similar to superchargers, and mechanical designs that allow the stacking of pumps. The most common variations are shown below (the drive gear is shown blue and the idler is shown purple).

Pump formulas:
Flow rate in US gal/min = Displacement X rpm/231 (displacement in in3/revolution)
Power in hp = US gal/min X (lbf/in³)/1714

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