What are External Gear Pumps?

A gear pump operates by enclosing a fixed volume within rotating gears to convey fluids in a smooth, pulse-free flow. There are two basic designs of gear pumps: the internal gear pump, which has two interlocking gears of different sizes, and the external gear pump, consisting of two identical interlocking gears supported by independent shafts. The three stages of operation for an external gear pump are filling, transfer, and delivery, with the volume minimized and fluid forced out under pressure during the delivery stage.

External gear pumps are compact and simple, offering higher pressure and throughput compared to vane and lobe pumps. They are suitable for pumping water, polymers, fuels, and chemical additives. Gear pumps can be run at high speeds, up to 700 rpm for larger helical or herringbone gear designs, and handle pressures up to 7250 psi (500 bar) for hydraulic power applications. These pumps find extensive use in various industries, including engines, gearboxes, hydraulic power applications, and fluid handling in harsh environments.

Although gear pumps have several advantages, they do have limitations. They require regular fluid lubrication and should not be run dry for extended periods. External gear pumps are less suitable for handling abrasive fluids due to tight tolerances and multiple bearings in the pumped medium. To reduce wear from abrasive solids, selecting pumps with higher capacity to operate at lower speeds is recommended. It is essential to ensure that gear pumps operate within their recommended speed and temperature range to prevent wear and performance degradation.

Over time, gear pumps may succumb to wear and increase flow slip, leading to reduced efficiency. Relief valves should be fitted in the system to protect downstream equipment from over-pressurization caused by blockages. Gear pumps are commonly used for various applications, such as water pumping, chemical mixing, industrial hydraulic systems, and more. However, they are not suitable for high-viscosity fluids or mediums with entrained solids due to their design and operating characteristics.

In conclusion, external gear pumps are reliable and widely used for fluid handling in various industries, offering accurate dosing and high-pressure output capabilities. While they have limitations related to wear and handling certain fluids, they remain a valuable and versatile choice for many applications.