Gear pumps have very few moving parts. They consist of two intermeshing gears. These pumps have a constant flow rate. They operate at pressures generally between 50 and 210 bar. Gear pumps operate at the highest speeds of any pumps at up to 3000-6000 rpm.
Advantages:
- They are inexpensive
- They have fixed-displacement
Disadvantages:
- Their volumetric efficiency is low
There are two types of gear pumps: external-gear pumps and internal-gear pumps.
External-gear pumps:
- In an external-gear pump, only one of the gear wheels, the drive gear, is connected to the drive. The other gear wheel, the driven gear, rotates in the opposite direction, so that the teeth of the rotating gear wheels interlock.
There are also double external-gear pumps, which combine two gear pumps driven by the same coupling shaft. A double external-gear pump has the advantage of supplying two independent hydraulic circuits, and also provides more flow to one circuit.
Internal-gear pumps:
- They have an eccentric internal gear wheel and an external gear wheel, also called a crown gear.
- When the external gear rotates, volume is created between the gear wheel profiles and the external gear teeth attached to the gear housing walls.
- The product is sucked up when the two wheels disengage.
Advantages:
- Internal-gear pumps are very quiet
- They provide a constant flow