Rotary pumps external gear

Rota.ry Lobe Pumps. Rotary lobe pumps are similar to gear pumps in principle. These pumps have an added advantage of noncontacting metal parts by use of external gears, which reduces the wear, but adds complexity. Low wear and improved shear characteristics make these pumps apphcable to the food industry, where cleanliness and absence of contamination are required. These pumps produce a strong pulsing flow that must be addressed. 

One of the most common rotary pumps is the external gear pump illustrated in Figure 4.11. The fixed casing contains two meshing gears of equal size. The driving gear is coupled to the drive shaft which transmits... 

Cutaway view of external gear (rotary) pump. 

More recently, HNP Mikrosysteme GmbH [14] has commercialized a type of rotary pump called micro annular gear pump. This t3q>e of pump is a positive displacement pump with an externally toothed rotor and internally toothed ring, which are assembled with a small eccentricity of their rotation axes with respect to each other. The rotation of the internal rotor forces the fluid pockets which are interlocked between two gears to flow. The pump flow rates vary from product to product, but are in a range of 1 pL/h to 1.2 1/min. Advantages of this product include accurate control of flow rate and minimum pulsation in delivery. 

External rotary gear pumps are particularly suitable for moderate-to-very high-kinematic viscosity liquids in the range of 100 to 500,000 centistokes for flow capacities to at least 1,500 gpm (0.252 mVs) and heads to at least 3,000 ft (914.4 m). They are moderately priced, but usually more expensive than radial centrifugal pumps. They cannot be used with liquids containing particles and do not give as smooth a flow rate as do radial centrifugal pumps. 

Many other specialized pumps are available for services that cannot be handled by radial centrifugal, external rotary gear, and plunger and piston reciprocating pumps. Specialized pumps are not considered here. Purchase-cost data are given next only for the three most commonly used types of pumps. 

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