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Internal gear pumps

Below you will find an overview of internal gear pumps from the manufacturer ZEIFLELDER Pumpen. Learn more about characteristics, special features and applications.


Internal gear pumps - overview​​



Internal gear pumps are positive displacement pumps.

However, due to their design, they belong to the gear pumps and represent a class of their own.


Pump head with internal gear rim, which is connected to the drive shaft. The externally toothed gear wheel is driven by the internal gear wheel rim. The externally toothed gear wheel is cantilevered in the pump cover. The drive unit usually consists of a coupling and a geared motor. However, there are also other designs such as direct-coupled motors, often in combination with a magnetic coupling.


Due to the asymmetrical position of the external gear wheel, the size of the delivery space changes during one revolution of the internal gear wheel rim, which pushes the medium from the suction side to the pressure side of the pump. The internal gear rim connected to the drive shaft drives the smaller gear. The liquid medium is conveyed horizontally or vertically, sometimes also with a 90° angle, depending on the design or orientation of the pump head. The gear wheels are lubricated by the medium.

The size, module and design, in combination with power and speed, determine the flow rate. The flow rate is variable by speed control or bypass solutions. The delivery pressure is determined by the back pressure on the pressure side of the system and is limited by the power limit of the machine and the gap losses.

Power range

Pressure: up to 16 bar

Flow rate: 0.6 to 290 m^3/h 

Viscosity: up to 1 - 200,000 mPas

Temperature: - 40 to 300 °C

Power: 75 kW 

Solids content: up to X% (always requires testing)

Solids size: variable (always requires testing)

Suction height: up to 4 m

Heating: electrical, thermal oil, steam, water


Internal gear pumps are suitable for pumping primarily clean, non-abrasive media; robust designs allow a certain amount of solids.

As positive displacement pumps, these machines are suitable for pumping low- to high-viscosity liquids. Different gear shapes ensure optimum pumping of the liquid 

Internal gear pumps are self-priming and relatively economical to purchase due to the small number of components.


In the field of positive displacement pumps, internal gear pumps are considered to be low-pulsation/free.

Sealing technology

Stuffing box packing, lip seals, single mechanical seals, double mechanical seals, magnetic coupling


Grey cast iron, cast steel, steel, stainless steel, other special alloys on request

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