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. 

External gear None Power input and heat generated increases with increasing viscosity May be suitable for handling viscosities up to 25 000 centristokes without modification. For high viscosities (a) Clearances may be increased (b) Speed reduced (c) Number of gear teeth reduced... 

External Gear Purnp Internal Gear Pump Three-Lobe Pump... 

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... 

The type of driver will be specified by the purchaser. The driver shall be sized to meet the maximum specified operating conditions, including bearing, mechanical seal, external gear, and coupling losses, as applicable, and shall be in accordance with the applicable specifications, as stated in the inquiry specification, data sheets, and order. The driver shall be suitable for satisfactory operation under the utility and site conditions specified. 

Figure 7.4. Performance of several kinds of pumps, (a) Comparison of small centrifugal and turbine pumps (Krista and Annett, 1940). (b) An axial flow pump operating at 880 rpm (Chem. Eng. Handbook, 1973). (c) An external gear pump like that of Figure 7.12(e) (Viking Pump Co.), (d) A screw-type positive displacement pump, (e) NPSH of reciprocating positive displacement pumps.

A pilot plant scale starch solution, approximately 300 l, was prepared in a stainless steel container equipped with a paddle wheel electric stirrer, steam-heated coils, steam injection, an external gear pump with recirculation capability, insulation surrounding the container, a container lid, and a vent. The starch solution was prepared with the same percentage composition and duration of heating as described for the laboratory scale process. The first batch was pimped into the "sizing box" of the slasher and utilized immediately hot as a conventional yarn treatment. 

Cutaway view of external gear (rotary) pump. 

FIGURE 4.5 Various types of pump impellers, continued (a) lobe type (b) internal gear type (c) vane type (d) impeller with stationary guiding diffuser vanes (e) impeller with volute discharge and (f) external gear type impeller. 

A steam-heated concentric displacement body is placed within this cylinder, which rotates slowly by an external-geared motor. Many segmented air guides are provided on the outer surface of the cylinder and are arranged at a suitable angle. The distance between these plates and the inner wall must be greater than the product film thickness. 

---