Overview of pump principles

External gear pump

Fig. 1: External gear

As a specialist for rotating displacement pumps, Scherzinger relies on external gear pumps for the delivery of aggressive, toxic and low-viscosity liquids. The rotor installed on the driven shaft of the gear pump transfers the rotary motion to the second rotor. The rotation displaces a liquid volume proportionate to the rotation speed. This way, liquids can be sucked into the pump and they can also be pumped at high pressures.

Due to the low internal friction coefficient, this pump principle is very energy efficient and there is little wear to the pump.

Gerotor pumps

Fig. 2: Gerotor

Gerotor pumps are mostly used as highly integrated units for oil lubrication in larger series. The cost benefits result from the use of sintered positive displacers in combination with simple case machining. Gerotor pumps are frequently designed as separate pumps without shafts, and can be mounted onto existing gear or intermediate shafts. Because of the high degree of integration into the customer’s system, no rotary shaft seal is required in most cases.

This type of gear pumps can also be easily set up to operate in either direction. In this case, the direction of flow does not change, regardless of the direction of rotation.

Internal gear pump

Fig. 3: Internal gear

Internal gear pumps, also called crescent pumps, are frequently used for applications that require low pulsation and a particularly smooth flow. Which is to say that the high degree of regularity of the discharge constitutes a particular advantage of internal gear pumps.

Due to the long sealing sections within the pump, very high suction heads and high differential pressure of up to 120 bar can be realized. The overall efficiency of this type of pump is excellent, as no compensation elements are required even at high pressures.

Overview of the benefits of the individual pump principles

  External gear Internal gear Gerotor
Maximum pressure o + ++
Low viscosity - + o
High viscosity + ++ +
Wear resistance + ++ +
Efficiency o ++ +
Costs ++ - o
Mainly used for Serial production, oil applications Single series, all-purpose liquids Serial production, diesel applications

Legend:    - poor   /   o acceptable   /   + good   /   ++ excellent


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