Pump Types and Pump Terminology

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nik.farid Member Join Date: Mar 2009 Posts: 7	Pump Types and Pump Terminology 04/10/2009 3:00 AM
	Can anybody tell me what's the difference between axial pumps, semi axial pumps and also centrifugal pumps. Also what is the meaning of the term head? have a bit of confusion in terns of high head and low head.. thank you..
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The Prof Guru Join Date: Aug 2006 Location: Western Australia Posts: 767 Good Answers: 58	#1 Re: Need some help.. 04/10/2009 3:53 AM
	Centrifugal pump impellers vary from radial flow (I think this is what you refer to as centrifugal) through Francis type through mixed flow (semi axial) through to propeller (axial). The specific speeds of these vary from 10 for a Radial to 300 for a propeller. Can be more clear on the meaning of this (and the units) if you can not find it on the internet. Head or Total head is the head in meters developed across the pump. Ther relationship between head and pressure is: Pressure = density x g x head. We use the term Head as it is basically independent of the density of the liquid being pumped, so the head versus flow curve is valid for all liquids (within limits of viscosity). The power curve shown is relative to density. High and low are relative terms, but higher head and lower flow is achieved at lower specific speeds and higher flow lower head is achieved at higher specific speed - normally. __________________ If you can't explain it simply, you don't understand it well enough. (A.E.)
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nik.farid Member Join Date: Mar 2009 Posts: 7	#4 In reply to #1 Thnx, anyway... 04/12/2009 5:55 PM
	anyway prof thnx, just i want to knw something... How does a pump can be categorized as good or bad in terms of the head value? Because now that i have understand the basic concept of centrifugal pumps; to convert kinetic energy into pressure energy in order to pump the fluid to the other path... and what makes me confused is that, when the value of head is high, the flow rate is low and when the value of head is low, the flow rate is high.. Can u plz explained this? Thank you..
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The Prof Guru Join Date: Aug 2006 Location: Western Australia Posts: 767 Good Answers: 58	#5 In reply to #4 Re: Thnx, anyway... 04/12/2009 10:23 PM
	It is not a matter of good or bad, but rather of what specific speed impeller is required to match the intended duty. The specific speed is simply a number that describes the hydraulic features of a pump impeller varying from radial to propeller as described before. If you forget the theory and just look at the shapes of the different impellers and the passage that a liquid will take through the impeller and pump then it is not difficult to imagine that a propeller will pump a greater volume flow than can be achieved through the relatively narrow passages of the radial impeller. By the same token it should be easy to imagine that the head developed by a radial design would be greater than by a propeller. The sites recommended by other posters are good and will give you the basics. If you can get hold of a second hand copy of Centrifugal Pumps Design and Application by Lobanoff and Ross it will give you most all you will need to know. __________________ If you can't explain it simply, you don't understand it well enough. (A.E.)
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Tim in Mexico Guru Join Date: Jul 2008 Location: Anywhere I may be at the time Posts: 661 Good Answers: 16	#2 Re: Pump Types and Pump Terminology 04/11/2009 5:54 AM
	Check out www.yesyen.com this site should be very helpful to you trying to get a handle on the basics. Then you could come back with more specific questions afterwards. You'll find some interesting and informative tutorials and games there to help you.
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Anonymous Poster	#3 Re: Pump Types and Pump Terminology 04/11/2009 7:18 PM
	Go here for a free book to download (it is mainly on centrifugal pumps though) http://www.lightmypump.com/pump_book.htm
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Anonymous Poster (1); nik.farid (1); The Prof (2); Tim in Mexico (1)

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