Gear Pumps, The Internal and External of it all.
Gear pumps are a type of positive displacement pump that use intermeshing gears to transfer fluid. They are extensively used in various industries, including automotive, chemical, and food processing, for applications such as lubrication, transfer of viscous fluids, and circulation of process fluids. Gear pumps consist of two gears, one driving gear and one driven gear, that rotate in opposite directions within a casing. As the gears rotate, the fluid enters the pump through the inlet port and is trapped in the spaces between the teeth of the gears and the casing. The fluid is then carried around the casing and discharged through the outlet port.
Gear pumps are known for their simplicity and durability, as they have few moving parts and can operate at high pressures and temperatures. However, they can generate significant noise and are prone to leakage, which can be mitigated with proper maintenance and selection of appropriate materials for the gears and casing. There are various types of gear pumps, including external gear pumps, internal gear pumps, and gerotor pumps, each with its own specific design and operating characteristics.
External gear pumps are the most common type of gear pump.
They consist of two gears with external teeth that mesh together.
As the gears rotate, the fluid is trapped in the spaces between the teeth and the pump casing.
The fluid is carried from the pump's inlet to the outlet, providing a continuous flow.
External gear pumps are known for their simplicity, compact design, and reliability.
They are used in various industries for low-to-medium pressure applications.
Internal gear pumps are characterized by an external gear (driving gear) and an internal gear (driven gear) with internal teeth.
The external gear drives the internal gear, causing fluid to be trapped and transported from the pump's inlet to the outlet.
Internal gear pumps are capable of handling higher pressures and viscosities compared to external gear pumps.
They offer precise flow control, smooth operation, and low noise levels.
Internal gear pumps are often used in applications requiring accurate metering, high viscosity fluids, and precise flow rates.
External and Internal Gear Pump Comparison
| Typically, 4 bushings which are immersed within the liquid | 2 Working Parts – Rotor & shaft, and idler gear |
| High Pressure design up to 30bar | 2 bushings for shaft support. One bearing within the liquid |
| High Flow Design (up to 300M³H) | Medium pressure designs up to 15 bar |
| Fixed End clearances meaning slip is inevitable | Up to 200M³H |
| Unable to handle solids | Adjustable end clearance. |
| Handle small solids |
Applications for Gear Pumps
Gear pumps are cornerstones in the petrochemical industry. They are used for crude oil, diesel oil, lube oil, pitch, and bitumen. They are also used for transporting chemicals such as sodium silicate, mixed chemicals, acids, plastics, isocyanates, and other chemicals that must be handled with care.
They are also used for adhesives, resins, ink and paint. They are especially popular in the pulp and paper industries, where they are used for acid, lye, soap, black liquor, latex, kaolin, lime and sludge.
The food industry uses them for a lot of tasty options, including molasses, vegetable oils, pet food, vegetable fats, fillers, sugar, chocolate, and cacao butter.
The following table lists some typical applications of external and internal gear pumps:
| Type of gear pump | External | Internal |
| Acids and caustic (stainless steel or composite construction) | * | * |
| Industrial, agricultural, and mobile hydraulic applications | * | * |
| Chemical mixing and blending | * | * |
| Chemical additive and polymer metering | * | * |
| Various fuel oils and lube oils | * | * |
| Alcohols and solvents | * | * |
| Resins and polymers | * | |
| Asphalt, bitumen, and tar | * | |
| Food products: corn syrup, peanut butter, cacao butter, chocolate, sugar, fillers, vegetable fats, vegetable oils, animal feed | * | |
Polyurethane foam (Isocyanate and polyol) | * | |
| Paint, inks, and pigments | * | |
| Soaps and surfactants | * | |
| Glycol | * |
If you need gear pumps you can trust Kelair to have the best options for sale. From fuel distribution and construction through to mining, manufacturing, earthmoving, transport, automotive, and oil/gas, we supply our gear pumps to a wide range of industries across Australia. Get in touch with our team today for recommendations on the best gear pump to suit your requirements.
How our experts at Kelair can help you:
- Design and cost a system or project.
- Customise and engineer solutions for your specific application.
- Provide spare parts and maintenance services.
- Pump Manuals and Technical Guides
- And so much more!