The gear pump is a positive displacement (PD) pump that uses gears to deliver the fluids. The gear forms a liquid seal at the pump inlet with a pumping chamber and creates a vacuum. The liquid sucked by the pump is located in the gear cavity and is led to the outlet channel. The gear pump provides smooth, pulsation-free flow at the speed of your gear.
Gear pumps have two main designs, internal and external gear pumps. The two interconnected gears of different sizes are present in the internal gear pump, one of which rotates inside the other.
The two interconnected gears are supported by different shafts present in the external gear pump. Usually, one gear is driven by a motor, and the motor drives another gear (deactivated). In some cases, both axes can be driven by motors. The shaft is supported by bearings on both sides of the casing.
The gear pumps have many advantages over submersible pumps, such as these pumps don’t have cavitation problems while submersible pumps have cavity problems. A gear pump doesn’t require initial priming, while a submersible requires initial priming. But submersible pumps are more efficient than gear pumps.
Types of Gear Pumps
The gear pump has the below-given types:
1) External Gear Pump
The external gear pumps use two external gears to replace the fluid without oil (the gears are lubricated). This mechanism is usually driven by one gear, which in turn drives the other gear. Flow regulation consists of three factors: the volume of the interdental cavity, the speed of the gear, and the amount of fluid returning to the inlet mechanism (depending on the bearings).
There are three main types of external gears: hook teeth, helical teeth, and predatory teeth. Spiral forms and pruning fish produce more current at higher pressures and are quieter but require more direct pressure than direct forms.
2) Internal Gear Pump
Internal gear pumps are widely used. They are commonly used for medium and low viscosity liquids such as solvents and baking oil and have a wide temperature range. It has no pulsation, fills itself, and can dry in a short time. This is the main gear pump variety.
Includes an internal gear, an ordinary gear, a crescent-shaped seal, and a casing. Fluid enters the suction port between the rotor teeth (large outer gear) and the lazy one (small inner gear).
The liquid passes through the pump between the tooth and the crescent. It separates the liquid crescent and acts as a seal between the intake port and the exhaust port. When the teeth are in front of the crescent seal, the liquid exits through the pump discharge port, gear spacing can be adjusted to withstand high temperatures, control high-pressure fluids, and resist wear.
These pumps rotate in both directions, so they can be used to load and unload containers. Since these pumps have only two moving parts and a spare box, they are reliable, easy to use, and easy to maintain.
However, these pumps are not suitable for high-speed, high-pressure applications. Only one bearing is used in the pump, so loading the console onto the bearing reduces bearing life.
Advantages and disadvantages of the external gear pump.
External gear pumps can operate at higher pressures than other types of pumps and generally offer a more compact and cost-effective design. The external gear pump works well in medium and low temperatures while maintaining a relatively high flow rate. The external gear pump design requires solid internal space and is ideal for batch applications due to its accurate flow rate. It also checks liquids with lower viscosity because the distance between the parts is small, so there is little leakage. However, due to the limited space between moving parts, external gear pumps usually have a higher wear rate than other types of pumps.
Advantages and disadvantages of Internal Gear Pumps
The internal gear pump works best at medium pressure. It is generally larger and more expensive than its foreign counterpart. However, it has many advantages over external gear pumps:
- It has a higher adsorption capacity and is suitable for handling liquids with higher viscosity.
- It is stronger because it has weaker mechanical clearance.
- Loose mechanical loosening allows for better handling of higher fluid temperatures (more thermal expansion space for components), making it an ideal choice for high-temperature pumping systems such as oil heat transfer.
- The internal gear pumps have capability of providing direct two-way (two-way) fluid flow. This is useful when a pump is needed for two purposes, such as filling and emptying containers.
Applications of Gear Pumps
Some common applications of internal gear pumps are:
- Resins and polymers
- Alcohols and solvents
- Bitumen, bitumen and bitumen
- Polyurethane foam (isocyanate and polyol)
- Foods like corn syrup, chocolate, and peanut butter
- Dyes, inks, and pigments
- Soap and surfactant
- Glycol
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