A gear pump is a type of rotary pump that transports fluid using rotating gears. It works by pushing fluid through the pump, creating a vacuum pressure and completing its function with two or more intermeshing gears. Gear pumps can generate very high pressures and are among the most common pumps used in hydraulic fluid power applications. The invention of the gear pump dates back to the 1600s, attributed to Johanner Kepler. They are widely used in chemical plants to pump high-viscosity fluids. Gear pumps deliver a fixed volume of fluid per revolution, providing smooth, pulsation-free flow proportional to the rotation speed of the gears. They are suitable for pumping highly viscous fluids such as plastics, oils, paints, adhesives, and soaps.
Working Principle of Gear Pumps
Gear pumps operate on the principle of positive displacement, meaning they pump a fixed amount of fluid per revolution. The idle and drive gears rotate to create suction at the pump inlet, drawing fluid in. Fluid is trapped between the gear teeth and the pump casing, directed to the discharge point. As the volume between the gears decreases, pressure builds up, pushing the fluid out. The flow rate depends on the gear speed (rpm) and the internal clearances; as the pump wears, internal slip increases.
Features of Gear Pumps
Gear pumps are compact and simple, with a limited number of moving parts.
They provide higher pressure and efficiency than vane pumps, although they may not match the high flow rates of centrifugal pumps or the high pressures of piston pumps.
Designed for pumping oils and other high-viscosity fluids.
Often used for metering and mixing operations.
Can handle aggressive fluids if designed accordingly.
Typically made from cast iron or stainless steel.
Applications of Gear Pumps
Gear pumps are commonly used for pumping high-viscosity fluids such as:
- Oils
- Paints
- Resins
- Food products
They are ideal for applications requiring precise dosing or high-pressure output. Since the output of a gear pump is largely unaffected by backpressure, they can be used even in irregular feed conditions.
Types of Gear Pumps
Gear pumps are generally classified as external gear pumps or internal gear pumps.
External Gear Pumps:
- Commonly used in hydraulic power applications, lifting machinery, or mobile equipment.
- Useful where electrically driven systems are bulky, costly, or impractical.
- Moderate efficiency and relatively low cost.
- Can transfer fuels such as gasoline, diesel, and kerosene, and handle high-pressure applications in some hydraulic devices.
Internal Gear Pumps:
- Also called internal or idler gear pumps.
- Use an internal gear inside an outer gear to generate flow.
- As the gears rotate, fluid is drawn into expanding cavities and pushed toward the discharge.
- Capable of handling a variety of chemicals, resins, and viscous fluids.