Using orifice plate for minimum flow protection

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Anonymous Poster	Using orifice plate for minimum flow protection 05/20/2010 6:48 AM
	Why / what would be the reason for you to use an orifice plate for minimum flow protection for a pump? Since the discharge side always has a higher pressure, the discharge fluid will keep on flowing through the orifice plate until the delta P is zero (meaning a big increase in suction head), basically, you will be constantly sucking discharge fluid into the suction and then pumping it again, which sounds like a total waste of energy? Thank you.
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Anonymous Poster	#1 Re: Using orifice plate for minimum flow protection 05/20/2010 7:46 AM
	Can you pleas draw a line diagram? I am atleast unable to understand the schematic. The way you describ, there should be a pressure relief valve and not an orifice plate to protect the pump (especially seals of it) against any sudden/accidental outlet blockage. Orifice byepass, I have never come across.
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deekay Member Join Date: May 2010 Location: Kuala Lumpur Posts: 5	#2 Re: Using orifice plate for minimum flow protection 05/21/2010 3:46 AM
	It seems to me that you should be using a relief valve on the discharge side of the pump. This is even more essential if you have a positive displacement pump. I have never heard of orifice plates being used for minimum flow protection. Please review this or you could damage the pump big time.
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Codemaster Guru Join Date: Jul 2005 Location: Stoke-on-Trent, UK Posts: 4496 Good Answers: 137	#3 Re: Using orifice plate for minimum flow protection 05/21/2010 6:15 AM
	It's to avoid no-flow (deadhead) condition on the pump if all downstream valves are closed. Orifice plate is in a pipe taken from the pump discharge, and routed back to the suction tank. Best not returned to the pump suction pipe as the fluid would soon overheat. Orifice sized for the minimum flow the pump is happy with, which is usually quite low, a few % of design flow. In normal operation there is still a flow through the orifice, so this flow must be added to the required delivery flow when spec-ing the pump. Cheers...........Codey __________________ Give masochists a fair crack of the whip
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ducon Guru Join Date: Dec 2006 Location: Hop around Toronto, New York & Karachi Posts: 1876 Good Answers: 19	#4 Re: Using orifice plate for minimum flow protection 05/22/2010 7:17 AM
	Check your pump flow gpm/outlet pressure/motor HP. in one of my application a grossly oversized pump with heavy HP motor was taken for personal money-making reason and to coverup an orifice was fitted with an expensive water pressure reducing valve. This is but one application of orfice. __________________ I not only use all the brains that I have, but all that I can borrow. Woodrow Wilson
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Anonymous Poster	#5 Re: Using orifice plate for minimum flow protection 05/26/2010 1:14 PM
	Thank you for your replies, is there a specifications which guides you in selecting a proper orifice plate?
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Codemaster Guru Join Date: Jul 2005 Location: Stoke-on-Trent, UK Posts: 4496 Good Answers: 137	#6 In reply to #5 Re: Using orifice plate for minimum flow protection 05/27/2010 6:28 AM
	Yes, it's the usual orifice flow formula. You need to know flow = minimum pump flow (see #3) and ΔP across the orifice, likely to be close to pump closed-valve pressure rise, as pipe friction negligible at the minimum flow, unless the system is unusual. Then you can calculate orifice diameter. Cheers............Codey __________________ Give masochists a fair crack of the whip
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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	#7 Re: Using orifice plate for minimum flow protection 10/02/2024 6:10 AM
	The P&ID cannot be seen from here. Pass the installation through a HazOp Study, and see what the outcome is. __________________ "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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Anonymous Poster (2); Codemaster (2); deekay (1); ducon (1); PWSlack (1)

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