Service Manual # 67
Page 5 of 36
Section 2: The Pumping Principle
Figure 1 - Internal Gear Pumping Principle
Tuthill 6000, 7000 & 8000 Series pumps employ the internal gear pumping principle (see Figure 1).
There are only two moving parts. Pumping action is based on a rotor, idler gear and crescent-
shaped partition cast integral with the cover.
Power applied to the rotor is transmitted to the idler gear with which it meshes. The space between
the outside diameter of the idler and the inside diameter of the rotor is sealed by the crescent.
As the pump starts, the teeth come out of mesh, increasing the volume. This creates a partial
vacuum, drawing the liquid into the pump through the suction port.
The liquid fills the spaces between the teeth of the idler and the rotor and is carried past the
crescent partition through the pressure side of the pump.
When the teeth mesh on the pressure side, the liquid is forced from the spaces and out through the
discharge port.
Section 3: Proper Installation
Unsatisfactory pump installations are usually characterized by poor suction conditions for the
specific liquid being handled. Suction conditions should be minimized to prevent vaporization of the
liquid. If vacuum conditions force the liquid to vaporize, cavitation will occur, resulting in loss of
capacity, premature wear and noisy operation.
For optimum pump performance, the suction line must be at least as large as the corresponding
pump port. It should be as short as possible in order to avoid excessive pressure drops and must
be airtight. The placement of a strainer on the suction side of the pump will restrict any solids or
abrasives from entering the pump which could cause internal damage.
Note: Pipe line friction increases at a rapid rate with an increase in viscosity. For a given pump and
motor, larger pipe lines are necessary to maintain the same pump pressure when changing from a
thin fluid to a thick one.
When handling high viscosity liquids, the speed of the pump must be reduced and the size of the
lines increased to prevent cavitation.
Summary of Contents for 6000
Page 28: ...Service Manual 67 Page 28 of 36 Figure 3 Typical 6110 Series Pump ...
Page 29: ...Service Manual 67 Page 29 of 36 Figure 4 Typical 7110 Series Pump ...
Page 30: ...Service Manual 67 Page 30 of 36 Figure 5 Typical 6200 Series Pump ...
Page 31: ...Service Manual 67 Page 31 of 36 Figure 6 Typical 6210 Series Pump ...
Page 32: ...Service Manual 67 Page 32 of 36 Figure 7 Typical 6300 7200 8200 Series Pump ...
Page 33: ...Service Manual 67 Page 33 of 36 Figure 8 Typical 6310 7210 8210 Series Pump ...