Choosing a gear type

What types of gearing are there?

There are basically three different gear tooth systems for gear pumps.

Spur, helical and herringbone gearings are available to choose from for the pumps. Each of these types of tooth system has different properties that are decisive for the use of the type of gearing. The most commonly used system is spur gearing. Classically, involute gearing is used for gear pumps.

Qualitative differences in pulsation behaviour

When pumping fluids, it is often important for the process that a constant product flow is present. Gear pumps are used in the plastics industry, for example, to produce profiles or foils. To ensure consistently high product quality, the product flow must not pulsate, as this would result in uneven layer thicknesses. The graph qualitatively illustrates the different pulsation behaviour of the various tooth systems. If particularly shear-sensitive media are conveyed or the process requires a low pulsation behaviour, a herringbone gearing is very suitable.

Compared to oscillating displacement pumps, the pulsation behaviour of gear pumps is significantly lower than that of piston diaphragm pumps, for example.

 

The types of gearing and areas of application

Spur gearing

Viscosities:
Low, medium and, as a special variant, also high viscosities
Differential pressure:
120 bar, as special version also up to 250 bar
Volumetric efficiency:
high
Pulsation:
exists

Helical gearing

Viscosities:
Medium to high viscosities
Differential pressure:
250 bar
Volumetric efficiency:
high
Pulsation:
Less pulsation than the spur gearing

Herringbone gearing

Viscosities:
Medium to high viscosities
Differential pressure:
250 bar
Volumetric efficiency:
Lower than with helical gearing
Pulsation:
low