Inplant Training

Topics: Electricity generation, Nuclear power, Turbine Pages: 9 (2048 words) Published: December 28, 2012
Centrifugal pumps

The applications  of  centrifugal  pumps  are  numerous; however, these pumps are most often used in buildings for the following purposes: To pump the general water supply. This includes both the overhead and pneumatic tank systems. In general water supply systems where the pump takes off directly from the city pressure main or where no suction lift is required, a centrifugal pump can be used. When a centrifugal pump is being used with a suction lift of no more than 15 feet is required, a pump with an automatic primer or a suction line equipped with a foot valve may be used. To provide booster service. In booster service, centrifugal pumps with in-take pressures from the city main operate only to boost this pressure. They may run continuously  or  automatically.  When  the  automatic type is not operating, the water flows by city pressure through  the  impellers. To pump the domestic water supply. In domestic water supply systems, the centrifugal pump is used in shallow wells (suction lift not over 22 feet), in deep wells (for greater depths than 22 feet), and in a complete pneumatic system with electric motors or gasoline engines.

To support the fire protection systems. Fire pumps usually are the centrifugal type, either single or multistage. Electricity, steam, or gasoline may drive them. Whatever the power supply, it must be permanent and, if steam, must have a constant minimum pressure of 50 pounds of steam. The pumps should agree with the specifications of the NFPA. Booster fire pumps have a low head to boost the pressure of the already available  city  supply

To provide a hot-water circulating service. Hot- water circulating pumps are centrifugal. They move water in a closed system and thus usually require only a low head, though the static pressure in the systems may be high. The pumps should be selected with attenti on to strength  of  casing,  efficient  stuffing  box,  freedom  from air  and  vapor  binding,  and  flexible  mounting. To provide sump drainage. Sump pumps are not classified as sewage pumps; however, they can be used as such. They may be vertical or horizontal centrifugal. The vertical type sump pump usually has the impeller submerged and the motor mounted above the pit. Units are equipped with an automatic switch operated by the float and are available in single or duplextype

* A centrifugal pump is basically a gear inside a bonnet (form-fitting housing). The pumped fluid enters the bonnet near the axis of rotation of the gear. Variability
* Centrifugal pumps can pump a wide variety of substances at variable rates of speed and volume. They are widely used as both water and air pumps in cars Scale
Centrifugal pumps are cheap

low maintaince

seldom &compactness

weight saving

adaptability to high-speed prime movers.
One  disadvantage  of  centrifugal  pumps  is their relatively poor suction power. Another  dis- advantage of centrifugal pumps is that they develop CAVITATION. Cavitation occurs when the velocity of a liquid increases to the point where the consequent pressure drop reaches the pressure of vaporization of the  liquid. When this happens, vapor pockets, or bubbles, form in the liquid and then later collapse when subjected to higher pressure at some other point in the flow. A centrifugal pump cannot pump air, therefore cannot self prime, like a positive displacement pump.

Applications of Reciprocating Pump
Reciprocating pumps has low discharge rate and high pressure ratios. For moderate pressures of the range 10 bar rotary pumps can be used but for sustained high pressure work of the range 500 bar reciprocating pumps are used. As the volume of fluid displaced per stroke is accurate the reciprocating pumps are used in metering application where a certain calculated amount...
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