CENT_PUM-NB.pdf

CENTRIFUGAL PUMPS e-notes: Dr.N.Balasubramanya Professor, Department of Civil Engineering M.S.Ramaiah Institute of Technology, Bangalore-560054 A pump is a hydraulic machine which converts mechanical energy into hydraulic energy or pressure energy. A centrifugal pump is also known as a Rotod ynamic pump or dynamic pressure pump. It works on the principl principlee of centrifugal centrifugal force. force. In this type of pump the liquid liquid is subjected subjected to whirling motion by the rotating impeller which is made of a numbe r of backward curved vanes. The liquid enters this impeller at its center or the e ye and gets discharged into the casing enclosing the outer edge of the impeller. The rise rise in the pressure head at any point/outlet of the impeller is Proportional to the square of the tangential velocity of the the u 2  liquid at that point (i.e, α  ) . Hence at the outlet of the impeller where the radius is 2g  more the rise In In pressure head will be more and the liquid will will be discharged at the outlet with a high pressure head. Due to this high pressure head, the liquid can be lifted to a higher higher level. Generally Generally centrifuga centrifugall pumps are made of the the radial flow flow type only. only. But there are also axial flow or propeller pumps which are particularly adopted for low heads. Advantages of centrifugal pumps:1. Its Its ini initi tial al cost cost is low low 2. Effi Effici cien ency cy is is high high.. 3. Discharge is uniform and continuous 4. Installation and maintenance is easy. 5. It can run at high speeds,without the risk of separation of flow Classification of centrifugal pumps Centrifugal pumps may be classified Into the following types 1.According to casing design a) Volute Volute pump b) diffus diffuser er or turbin turbinee pump pump 2. According to number of impellers a) Single Single stage stage pump b) multista multistage ge or multi impeller impeller pump pump 3. According to number of entrances to the impeller: (FOR FIGURES DOWNLOAD PRESENTATION) a) Sing Single le suct suctio ion n pump pump b) Doub Double le suct suctio ion n pum pump p 4. According to disposition of shaft a) Vert Vertic ical al shaf shaftt pump pump b) Hori Horizon zonta tall shaf shaftt pump pump 5. According to liquid handled a) Semi Semi ope open n impe impell ller er b) Open Open impe impell ller er pump pump

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6.According to specific speed a) Low specific specific speed speed or radial radial flow flow impelle impellerr pump pump b) Shro Shroud uded ed impe impell ller er c) Medium specific specific speed or mixed mixed flow flow impell impeller er pump pump c) High specific specific speed or axial flow type or propeller propeller pump. 7. According to head (H) • Low head if H