Reduced Bore vs Full Bore Ball Valve Flow Rate Change at the Constant Speed Pump

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phillipwon Associate Join Date: Nov 2011 Posts: 42	Reduced Bore vs Full Bore Ball Valve Flow Rate Change at the Constant Speed Pump 11/28/2011 7:52 AM
	Assume that we use - the pump only at the constant speed. - The 4 inch pipe - 4 inch full bore ball valve Cv= 1850 - 4*3 inch reduced bore ball valve Cv= 600 Suppose that the flow rate, Q, of the full bore ball valve is 52.5 USgpm and then pressure drop would be 0.0008013 psi. If we use reduced bore ball valve instead of full bore, the flow rate would be decreased in case we run the pump at the constant speed, same speed as full bore case, but pressure drop would be increased. I know how pressure drop of reduced bore ball valve can be calculated assuming the flow rate is the same between full bore and reduced bore, but supposed that we use the pump at only constant speed, can we calculate how much is the flow rate and the pressure drop in the reduced bore ball valve? Thanks in advance.
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lyn Guru Join Date: Oct 2008 Posts: 42355 Good Answers: 1693	#1 Re: reduced bore vs full bore ball valve flow rate change at the constant speed pump 11/28/2011 8:07 AM
	Yes, you can. Or, yes, you may, depending on the level of formality in your classroom.
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ajwinemaker Power-User Join Date: Dec 2008 Location: Australia Posts: 143 Good Answers: 24	#4 In reply to #1 Re: reduced bore vs full bore ball valve flow rate change at the constant speed pump 11/28/2011 5:48 PM
	GA for me for your wit
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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	#2 Re: Reduced Bore vs Full Bore Ball Valve Flow Rate Change at the Constant Speed Pump 11/28/2011 11:28 AM
	The things that are missing are the pump characteristic curve and the system characteristic curve. The operating point is where these two curves intersect. Adding some restriction such as a reduced bore ball valve alters the system characteristic curve. As to how much reduction in flow is achieved depends on the slope of the pump characteristic curve in the region of the operating point. Any reduction in flow is likely to be tiny in comparison with other features of the system; rarely is it worth calculating it in the real world as other considerations would tend to swamp the effect. __________________ "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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RVZ717 Guru Join Date: Oct 2008 Location: City of Roses. Posts: 2056 Good Answers: 101	#3 Re: Reduced Bore vs Full Bore Ball Valve Flow Rate Change at the Constant Speed Pump 11/28/2011 11:29 AM
	Of course it can be calculated, and a constant speed (not a variable displacement style) fixed displacement pump makes things easy. It looks like you have all the information you'll need to find the answer. These might be of help: http://www.engineeringtoolbox.com/pipes-fluid-flow-pressure-loss-t_18.html http://www.engineeringpage.com/engineering/pressure_drop.html www.pe.tamu.edu/.../1.7%20Pressure%20Drop%20Calculations.ppt __________________ Don't believe everything you read on the Internet!
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Tornado Guru Join Date: May 2009 Location: Richland, WA, USA Posts: 21017 Good Answers: 795	#5 Re: Reduced Bore vs Full Bore Ball Valve Flow Rate Change at the Constant Speed Pump 11/29/2011 3:07 AM
	My "constant speed" to you mean fixed displacement, or constant rpm? The answer depends on what type of pump it is. __________________ In vino veritas; in cervisia carmen; in aqua E. coli.
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phillipwon Associate Join Date: Nov 2011 Posts: 42	#6 Re: Reduced Bore vs Full Bore Ball Valve Flow Rate Change at the Constant Speed Pump 12/01/2011 12:18 AM
	Thanks for all of your comments. With your comments, I figure out how the flow rate and pressure drop is calculated in the reduced bore ball valve with the constant speed pump through using pump performance curve and resistance curve. Thank you very much all.
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ajwinemaker (1); lyn (1); phillipwon (1); PWSlack (1); RVZ717 (1); Tornado (1)

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