Centrifugal pressure developed

Booster Pump. Use of a centrifugal booster pump avoids a low intake pressure, particularly for large, high volume units. A low pressure (>26.6 kPa (200 mm Hg)) on the iatake of a timing pump can cause vaporization of the product. The booster pump is ia the circuit ahead of the timing pump and operates only when the FDV is ia forward flow, the metering pump is ia operation, and the pasteurized product is at least 7 kPa (1 psi) above the maximum pressure developed by the booster pump (Fig. 8). 

The purpose of a centrifugal pump is to increase the pressure of a liquid in order to move it through a piping system. The pump is driven by a motor, which must provide sufficient power to operate the pump at the desired conditions. You wish to find the pressure developed by a pump operating at a flow rate of 300 gpm with an oil having a specific gravity (SG) of 0.8 and a viscosity of 20 cP, and the required horsepower for the motor to drive the pump. The pump has an impeller diameter of 10 in., and the motor runs at 1200 rpm. 

The pressure developed by a centrifugal pump depends on the fluid density, the diameter of the pump impeller, the rotational speed of the impeller, and the volumetric flow rate through the pump (centrifugal pumps are not recommended for highly viscous fluids, so viscosity is not commonly an important variable). Furthermore, the pressure developed by the pump is commonly expressed as the pump head, which is the height of a column of the fluid in the pump that exerts the same pressure as the pump pressure. 

The pressure developed by a centrifugal pump for Newtonian liquids that are not highly viscous depends upon the liquid density, the impeller diameter, the rotational speed, and the volumetric flow rate. 

Thus if a centrifugal pump develops a total head of 100 m when pumping a liquid of density p = 1000 kg/m3, the pressure developed is 981000 Pa while for p = 917 kg/m3 the pressure developed is 900000 Pa. 

Equation 4.10 shows that when a centrifugal pump runs on air, the pressure developed is very small. In fact, a conventional centrifugal pump can never prime itself when operating on a suction lift. 

A centrifugal pump develops the same feet of head, regardless of the density of the liquid pumped, as long as the flow is constant. This statement is valid as long as the viscosity of the liquid is below 40 cp or 200 SSU (Saybolt Seconds Universal). But, as process operators or engineers, we are not interested in feet of head. We are interested only in pressure. Differential pressure is related to differential feet of head as follows ... 

A quite unconventional approach to internal fission-event detection was a device called the spinner. It operates on the same principle as the cloud chamber. The instrument, Figure 7, consists of a glass cylinder with glass arms filled with about one liter of the sample solution. Upon rotation, a negative pressure develops in the solution through the action of centrifugal forces. The solvent does not evaporate, however, but remains in a metastable... 

The objective of these experiments is to develop an aqueous suspension of silicon nitride containing 50-70 w/o solids for centrifugal/pressure casting of crack free NSF (Net Shape Formed) specimens. This requires development of suitable dispersant-binder system(s). Slips were developed using both alcohol milled (baseline) and water milled powders. 

In many cases, for example a plate and frame or a leaf press operated with the suspension supplied from a centrifugal pump, the early stages of fdtration are conducted at a nearly constant rate. As the cake becomes thicker and offers more resistance to the flow, the pressure developed by the pump becomes a limiting factor and the filtration proceeds at a nearly constant pressure. For such a combined operation, the plot of Ap against time is as shown in Figure 9.8. The equations are (see equation 9.23)... 

Consider now compaction in the centrifuge. In the decanter centrifuge the geometry is quite different, as illustrated in Figure 4.13. Nevertheless, the equivalent pressure heads may be derived using equation (4.61) for pressure. Pr, developed at radius r within a centrifuge. In equation (4.61) an expression is given for the pressure developed at radius r with liquor above to a level of radius rj. In the present case, it is required to know the pressure of the head of cake, at the bowl wall radius, r2, with the surface of the cake at radius, ri. Thus, meeds to be replaced by r2, and ri by r in equation (4.61). 

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