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External Gears

External Gears. Dinesh Bakthavatsalam 20192297 4M-I September 30 th , 2005. External Pumps Overview. External gear pumps are a popular pumping principle and are often found in lubrication pumps in machine tools, in fluid power transfer units, and as oil pumps in engines

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External Gears

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  1. External Gears Dinesh Bakthavatsalam 20192297 4M-I September 30th , 2005

  2. External Pumps Overview • External gear pumps are a popular pumping principle and are often found in lubrication pumps in machine tools, in fluid power transfer units, and as oil pumps in engines • External gear pumps can come in single or double (shown, left) pump configurations with spur, helical, and herringbone gears • Small external gear pumps usually operate at 1750 or 3450 rpm and larger models operate at speeds up to 640 rpm. • Reduced speeds with high-viscosity liquids results in greater efficiency. • The design of external gear pumps allows them to be made to close tolerances. • Tighter internal clearances provide for a more reliable measure of liquid passing through a pump and for greater flow control.

  3. How External Gear Pumps Work • The external gear pump uses two identical gears rotating against each other • One gear is driven by a motor and it in turn drives the other gear. • Liquid flows into the cavity and is trapped by the gear teeth as they rotate. • Liquid travels around the interior of the casing in the pockets between the teeth and the casing • Finally, the meshing of the gears forces liquid through the outlet port under pressure.

  4. ADVANTAGES High speed. Medium pressure. No overhung bearing loads. Relatively quiet operation. Design accommodates wide variety of materials. DISADVANTAGES Four bushings in liquid area. No solids allowed. Fixed End Clearances. Advantages & Disadvantages

  5. Applications • Industrial and mobile applications • Fuel and lubrication • Metering • Mixing and blending (double pump) • Hydraulic applications • OEM configurations • Precise metering applications • Low-volume transfers • Light or medium duty

  6. Materials of Construction • Externals (head, casing, bracket) - Iron, ductile iron, steel, stainless steel. • Internals (rotor, idler) - Steel, stainless steel. • Bushing - Carbon, bronze, silicon carbide. • Shaft Seal - Packing, lip seal, component mechanical seal, magnetically-driven pump.

  7. Sources: www.wikepedia.com www.pumpschool.com/principles/external.htm

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