Pump head

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santoshp9 Active Contributor Join Date: May 2010 Posts: 11	Pump head 07/02/2010 6:50 AM
	Dear sir, I have evaluating one pump 2100m3/hr,29m head of sp. gravity 1.1 with viscosity of 10cp,the vendor has selected pump RPM 470 & impeller dia 922mm with 79% efficiency motor of 1450rpm & 260Kw. As per tip speed the shutoff head I have calculated is 26.2m,Now I am in doubt wheather this pump will work for my required head of 29m. please advise me whether I am on right path of calculating the shut off head by tip speed(470rpm & 922mm dia.).
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PWSlack Guru Join Date: Jan 2007 Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on. Posts: 32175 Good Answers: 839	#1 Re: Pump head 07/02/2010 7:02 AM
	The tip speed is irrelevant, as the shut-off head depends upon the passing clearances in the casing and the detailed impeller design, the performance of which will be on the vendor's pump curve. 2100m³/h = 0.58m³/s. 29m head @ 1100kg/m³ and 9.81m/s²= 3.13 x 10⁵ N/m². Pump duty @79% is 231kW, so the motor seems large enough. Does the vendor's pump curve at 470rpm pass through 2100m³/h and 29m head, the purchaser's duty point? If not, then the pump may be wrong and the selection needs to be revisited with a view to determining whether the pump curve selected is acceptable. If it does then it is right. Buy the pump. __________________ "Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
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The Prof Guru Join Date: Aug 2006 Location: Western Australia Posts: 767 Good Answers: 58	#2 Re: Pump head 07/02/2010 8:57 AM
	Why oh why would your vendor choose to insert a gearbox or any other speed changing maintenance increasing device. Why not go for nominal 1500 rpm motor and pump (- slip is about 1450). You do not give NPSHa, but a double entry between bearing axially split pump will do most duties. Something like a KSB Omega (there are many other manufacturers of similar style pumps). You would then have direct drive at 1450 rpm and a much smaller diameter impeller - around 350 mm or so. __________________ If you can't explain it simply, you don't understand it well enough. (A.E.)
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Anonymous Poster	#3 Re: Pump head 07/03/2010 5:53 AM
	Dear Santoshp9, It is very difficult actualy to answer whether you are in the right way to check the your vendor pumps proposing, because the installation you do not inform,,what is the pipe diameter, and what is it the length, and what the installation facilities, and what the pipe materials, because the actual head can be calculated is all of it are informed. Anyway...if your way to calculate the head is correct, it means your pump head is bigger than actuall head meaning it is work.....and power usage can be checked by the formula density x total head x gravity....if this power smaller than installed motor it means the pum p will working well..........
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Kaisan Power-User Join Date: Nov 2009 Posts: 296 Good Answers: 27	#4 Re: Pump head 07/03/2010 2:45 PM
	Just taking a break from watching the ladies doubles and getting ready to watch Spain win. Quick read of this question and interesting to note that PW got GA and the prof got off topic. Going to have to think about this - "tip speed is irrelevant" ????????????????? Where did all the "laws" of similitude go? __________________ I have no special talent. I am only passionately curious. Albert E
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Anonymous Poster (1); Kaisan (1); PWSlack (1); The Prof (1)

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