Gear pump
A gear pump uses the meshing of gears
to pump fluid by displacement.[1] They
are one of the most common types of
pumps for hydraulic fluid power
applications. The gear pump was
invented around 1600 by Johannes
Kepler.[2]
An exploded view of an external gear pump.
Fluid flow in an external gear pump
Water flows from left to right in this internal gear
pump.
Oil pump from a scooter engine
Gear pumps are also widely used in
chemical installations to pump high
viscosity fluids. There are two main
variations: external gear pumps which
use two external spur gears, and internal
gear pumps which use an external and an
internal spur gears (internal spur gear
teeth face inwards, see below). Gear
pumps are positive displacement (or fixed
displacement), meaning they pump a
constant amount of fluid for each
revolution. Some gear pumps are
designed to function as either a motor or
a pump.
Theory of operation
As the gears rotate they separate on the
intake side of the pump, creating a void
and suction which is filled by fluid. The
fluid is carried by the gears to the
discharge side of the pump, where the
meshing of the gears displaces the fluid.
The mechanical clearances are small— in
the order of 10 μm. The tight clearances,
along with the speed of rotation,
effectively prevent the fluid from leaking
backwards.
The rigid design of the gears and houses
allow for very high pressures and the
ability to pump highly viscous fluids.
Many variations exist, including helical
and herringbone gear sets (instead of
spur gears), lobe shaped rotors similar to
Roots blowers (commonly used as
superchargers), and mechanical designs
that allow the stacking of pumps. The
most common variations are shown
below (the drive gear is shown blue and
the idler is shown purple).
External gear pump design for hydraulic
power applications.
Internal gear (Gerotor) pump design for
automotive oil pumps.
Internal gear (Crescent Internal Gear )
pump design for high viscosity fluids.
An external precision gear pump is
usually limited to a maximum working
pressure of 210 bars (21,000 kPa) and a
maximum speed of 3,000 rpm. Some
manufacturers produce gear pumps with
higher working pressures and speeds but
these types of pumps tend to be noisy
and special precautions may have to be
made.[3]
Suction and pressure ports need to
interface where the gears mesh (shown
as dim gray lines in the internal pump
images). Some internal gear pumps have
an additional, crescent-shaped seal
(shown above, right). This crescent
functions to keep the gears separated
and also reduces eddy currents.
Pump formulas:
Flow rate in US gal/min = Pump
Capacity × rpm
Power in hp = US gal/min ×
(lbf/in2)/1714
Generally used in:
Petrochemicals: Pure or filled bitumen,
pitch, diesel oil, crude oil, lube oil etc.
Chemicals: Sodium silicate, acids,
plastics, mixed chemicals, isocyanates
etc.
Paint and ink.
Resins and adhesives.
Pulp and paper: acid, soap, lye, black
liquor, kaolin, lime, latex, sludge etc.
Food: Chocolate, cacao butter, fillers,
sugar, vegetable fats and oils,
molasses, animal food etc.
See also
Gerotor
Hydraulic pump
Vane pump
References
1. "Welcome to the Hydraulic Institute" .
Pumps.org. Archived from the original
on 2013-06-26. Retrieved 2013-08-18.
2. Frank Prager, Kepler as inventor, Vistas in
Astronomy, Volume 18, 1975, Pages 887889, https://doi.org/10.1016/00836656(75)90184-1 .
3. Pinches, M J (2000). Kempe's Engineers
Year-Book, p. 2070. Miller Freeman, Kent.
ISBN 0863824420.
External links
Wikimedia Commons has media
related to Gear pump.
External gear pump description
Internal gear pump description
Retrieved from
"https://en.wikipedia.org/w/index.php?
title=Gear_pump&oldid=1009617598"
Last edited 2 months ago by Tom.Reding
Content is available under CC BY-SA 3.0 unless
otherwise noted.