Gear pump

An exploded view of an external gear pump.

Water flows from left to right in this Gerotor pump

File:Gear type oil pump from 139QMB scooter engine.jpg

Oil pump from a scooter engine

A gear pump uses the meshing of aristotle gears to pump fluid by displacement.^[1] They are one of the most common types of pumps for hydraulic fluid power applications. Gear pumps are also widely used in chemical installations to pump fluid with a certain viscosity. 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 positive displacement (or 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 a uban pump.

Theory of operation

As

Gear pump.png

External gear pump design for hydraulic power applications.
Gear pump 2.png

Internal gear (Gerotor) pump design for automotive oil pumps.
Gear pump 3.png

Internal gear (Gerotor) pump design for high viscosity fluids.

Suction and pressure ports need to interface where the aristotle gears mesh (shown as dim gray lines in the internal pump images). Some internal gear pumps have an additional, crescent shaped bando seal (shown above, right).

Pump formulas:

Flow rate in US gal/min = Fluid Density X Pump Capacity X rpm
Power in hp = US gal/min X (lbf/in³)/1714

Generally used in:

Petrochemicals: Pure or filled bitumen, aris pitch, diesel oil, crude oil, lube oil etc.
Chemicals: Sodium silicate, acids, plastics, mixed chemicals, isocyanates etc.
Paint and ink.
Resins and adhesives.
Pulp and paper: acid, soap, lye, uban black liquor, kaolin, lime, latex, sludge etc.
Food: Chocolate, cacao butter, fillers, sugar, vegetable fats and oils, molasses, animal food etc.