Pumps and Pumping

Pumps are devices for supplying energy or head to a flowing liquid in order to overcome head losses due to friction and also, if necessary, to raise the liquid to a higher level. The head imparted to a flowing liquid by a pump is known as the total head Ah. If a pump is placed between points 1 and 2 in a pipeline, the heads for steady flow are related by equation 1.14 

In equation 1.14, z, P/(pg), and u2/(2ga) are the static, pressure and velocity heads respectively and hf is the head loss due to friction. The dimensionless velocity distribution factor a is for laminar flow and approximately 1 for turbulent flow. 

For a liquid of density p flowing with a constant mean velocity u through a pipeline of circular cross section and constant diameter between points 1 and 2 separated by a pump, equation 1.14 can be written as 

For the most part, pumps can be classified into centrifugal and positive displacement pumps. 

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The need for redundancy in the culture system needs to be assessed. Failure of a well pump that brings up water to supply a static pond system may not be a serious problem in countries where new pumps can be purchased in a nearby town. However, it can be disastrous in developing countries where new pumps and pump parts are often not available, but must be ordered from another country. Several weeks or months may pass before the situation can be remedied unless the culturist maintains a selection of spares. 

A small rating submersible motor Submersible pump and pump in disassembled condition fipeq a... 

Lift pumps and pumps in suction lift conditions. 

Be aware that in some cases, you ll have to live with cavitation. Many pumps suffer cavitation for reasons of inadequate design, hor example, when operating only one pump in a parallel system, this pump tends to go into cavitation. Pumps that perform more than one dut through a valve manifold tend to suffer cavitation. Pumps that fill and drain tanks from the bottom tend to suffer cavitation. The last pump drawing on a suction header tends to cavitate. And of course vacuum pumps and pumps in a high suction lift arc candidates for cavitation. 

The majority of centrifugal pumps have performance curves with the aforementioned profiles. Of course, special design pumps have curves with variations. Eor example, positive displacement pumps, multi-stage pumps, regenerative turbine type pumps, and pumps with a high specific speed (Ns) fall outside the norm. But you ll find that the standard pump curve profiles are applicable to about 95% of all pumps in the majority of industrial plants. The important thing is to become familiar with pump curves and know how to interpret the information. 

Forced circulation Viscous and solid-containing liquids can be circulated. Enables an erosion-fouling balance. Circulation rate can be controlled. Relatively expensive due to extra shell volume. Cost of pump and pumping. Leakage of material at stuffing box. 

Rotary pumps with volume capacities up to 50 gal/min are considered to be small-volume capacity pumps. Pumps with volume capacities from 50 to 500 gal/min are moderate-volume capacity pumps. And pumps with volume capacities beyond 500 gal/min are large-volume capacity pumps. 

Turton, R. K. An Introductory Guide to Pumps and Pumping Systems (Mechanical Engineering Publications. London. 1993)... 

Now let us look at the systems and the components of the systems. Reports in the field are virtually mute on many small but annoying problems, which almost invariably accompany the operation of seawater RO systems. Here are some which have plagued us, starting with the pumps. I will not identify manufacturers, as I have avoided reference to any in this writeup. It is not my objective to accuse anyone. I just offer these comments in the hope to encourage those who I hope are aware of their product problems in the field and failures to rectify those for the benefit of all. I feel that considerably greater attention must be placed on pumps and pump materials selection for seawater RO use in order to improve reliability, simplify maintenance, and reduce failure frequency in the pump operations, and in turn improve on the RO system water supply capability. 

The diaphragm controller is therefore closed. When the system is started up, the connecting line between the vacuum pump and pump valve V2 is first evacuated. As soon as the pressure drops below the maximum switching point, valve V1 closes. When the pressure falls below the minimum switching point, valve V2 opens. 

Pumps and Pumping Systems Table 3.6 kn values for the Roots pump... 

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