A gear pump is a type of positive displacement pump that uses rotating gears to transfer fluids. It operates on the principle of trapping and displacing a fixed amount of fluid with each rotation of the gears. As the gears rotate, they create a low-pressure area at the inlet, allowing fluid to enter the pump.
There are two main types of gear pumps: external and internal. External gear pumps have two identical gears that mesh together and rotate in opposite directions. Internal gear pumps have one larger gear (rotor) and one smaller gear (idler) that fit inside the rotor and rotate in the same direction.
The following table summarizes the main differences between external and internal gear pumps:
| External Gear Pump | Internal Gear Pump |
|---|---|
| Two identical gears | One larger gear and one smaller gear |
| Gears rotate in opposite directions | Gears rotate in the same direction |
| Fluid is trapped between the gear teeth and the casing | Fluid is trapped between the gear teeth and the crescent-shaped partition |
| Higher pressure and flow rate | Lower pressure and flow rate |
| More noise and vibration | Less noise and vibration |
| More wear and tear | Less wear and tear |
| Suitable for low to medium viscosity fluids | Suitable for medium to high viscosity fluids |
The working principle of both types of gear pumps is similar. The fluid enters the pump at the inlet port, where it is trapped between the gear teeth and the casing (or the crescent). As the gears rotate, the fluid is carried along the pump chamber to the outlet port, where it is discharged. The amount of fluid delivered by the pump depends on the size and speed of the gears, as well as the clearance between the gears and the casing.
Gear pumps are widely used in various industries, such as oil and gas, chemical, food and beverage, and hydraulic systems. They can handle a variety of fluids, such as oils, fuels, paints, resins, adhesives, and molasses. Some of the advantages of gear pumps are:
- They are simple, compact, and efficient
- They provide a constant and pulseless flow
- They can operate at high pressures and temperatures
- They are self-priming and easy to maintain
Some of the disadvantages of gear pumps are:
- They are sensitive to contamination and abrasion
- They have limited suction capability and require positive inlet pressure
- They have high leakage and slip due to the clearance between the gears and the casing
- They are not suitable for fluids with solids or high viscosity
