1. Internal External Gear Pump
By Andrew McKinney

2. External Gear Pump
Internal Gear Pump
Objective: Compare the two pumps

3. External Gear Pump Been around since the beginning oil pump industry
Used for high pressure applications (pulse free fluid flow)
Smaller - operate at rpm or rpm
Larger operate 640 rpm
Can handle viscous and water type liquids well
Thick liquids speed must be properly set (small meshing time)
True involute gear form (contour gear curved)

4. Internal Gear Pump Crescent pump Less than 100 years old
Generally run at rpm
Smaller ones run at rpm (same as external)
Fairly long meshing time (allowing higher speeds with thicker fluids than external)
Not true involute gear form
$$$

5. Pump Handling Comparison Difference in Pressure
Materials
Metals of various types and hardness through to plastics of various types and hardness
Metal allow for high temperatures and aggressive products
Pump Handling Comparison
Abrasives
Thin liquids
Viscous
Solids Dry
Difference in Pressure
Internal
Good
Excellent
Poor
Average
External

6. Stack Up References Internal pump, more modern pump
Both have a pulse free fluid flow
External pump, cheaper
External pump has to run slower with thicker fluids
External involute form allows for less wear and tear
Internal pump handles abrasive and viscous fluids a lot better
References