Does your loader require maintenance, but you’re uncertain what parts to choose? Parts vary depending on the project, especially for gear pumps since they push fuels and oils to power the engine in 2 different designs. Unsure of which choice best suits your loader? Let’s examine the 2 types of gear pumps and their uses in loaders together.
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What are Gear Pumps?
Gear pumps work by rotating cogs or gears to create a vacuum seal within the pump, which repeatedly transfers fluids into enclosed cavities between the gears’ teeth to run the engine. This process drives one gear to engage the second, activating the loader’s motor to pump light fuels, oils, and solvents through the system.
The gear pump working cycle follows 3 stages:
- Filling—the gears create an expanded volume as they come out of the pump’s inlet side mesh, letting liquid flow into the cavities and be trapped by the teeth while rotating against the pump casing.
- Transfer—the trapped fluid moves from the inlet to the discharge around the casing.
- Delivery—volume is reduced as the gears interlock on the pump’s discharge side, forcing the fluid out under pressure.
Due to the close interlocking and tolerances between the gears, the pump casing develops suction, preventing fluid from leaking back to the center or discharge inlet. Both types of gear pumps are used to measure and blend various liquids due to their low internal volume providing a reliable measure and control of liquid flow through the pump.
Internal
Internal gear pumps operate when 2 identical gears of varied sizes—large and small—engage.
As demonstrated, the smaller idler is rotated by the larger rotor’s inner teeth to direct fluid, set off-center, and fitted with a crescent partition to seal the ports during transfer. Simple and compact, internal gears have better suction capabilities and compatibility with high viscosity fluids, bearing an operating range from 1cP (1 centipoise, or fluid viscosity unit) to over 1,000,000cP. Meaning any liquid from solvents and fuels to asphalt, paint, or tar flows easily.
External
External gear pumps operate when 2 identical, interlocking gears that engage side by side as a motor-driven gear moves its idler counterpart.
*Pump diagrams from Michael Smith Engineers
As seen above, external gears mesh via outer teeth to create volume and propel fluid around the gears towards the discharge. Compatible with water, fuels, and chemicals, external gear pumps’ close tolerances and shaft support allow operation up to 7250 psi (500 bar), with small models up to 3500 rpm and large ones at 700 rpm. These metrics make them perfect for engines, gearboxes, and hydraulic power applications like vehicles or loaders. In areas where electrical equipment is bulky or costly, external gear pumps reverse to provide motor power by pumping oil from elsewhere.
Whichever type of gear pump you choose, recognizing the differences between designs can ensure the best results in your loader projects. For help finding internal and external gear pumps at great prices, contact us at Loader Parts Source today!
