Comments for ekwestrel corp http://ekwestrel.com independent engineering consulting services Thu, 17 May 2012 05:22:06 +0000 hourly 1 http://wordpress.org/?v=3.3.2 Comment on Is there any confusion about NPSH? by Water Pumps Api | Water Pumps Directhttp://ekwestrel.com/npsh-clarification/npsh-clarification#comment-649 Water Pumps Api | Water Pumps Direct Thu, 17 May 2012 05:22:06 +0000 http://ekwestrel.com/?p=156#comment-649 [...] Is there any confusion about NPSH [...] [...] Is there any confusion about NPSH [...]

]]> Comment on Is there any confusion about NPSH? by ekwestrelhttp://ekwestrel.com/npsh-clarification/npsh-clarification#comment-625 ekwestrel Fri, 27 Apr 2012 19:14:50 +0000 http://ekwestrel.com/?p=156#comment-625 Excellent comment Scott. Production NPSHR test results can vary significantly due to the test conditions and the individual pump configuration. Often the production test is essentially a verification that the pump NPSHR falls below a guaranteed value at one or a few flow conditions. Manufacturers will balance the necessities for publishing a competitive level of NPSHR and meeting that level on test or in the field. Manufacturers would seldom have reason to add margin for the sake of system uncertainties. Notwithstanding, the term NPSH3 is coming into more common usage and clearly represents the NPSH definition for 3% head loss. Best, Randal Excellent comment Scott. Production NPSHR test results can vary significantly due to the test conditions and the individual pump configuration. Often the production test is essentially a verification that the pump NPSHR falls below a guaranteed value at one or a few flow conditions. Manufacturers will balance the necessities for publishing a competitive level of NPSHR and meeting that level on test or in the field. Manufacturers would seldom have reason to add margin for the sake of system uncertainties. Notwithstanding, the term NPSH3 is coming into more common usage and clearly represents the NPSH definition for 3% head loss. Best, Randal

]]> Comment on Is there any confusion about NPSH? by Scott Boysonhttp://ekwestrel.com/npsh-clarification/npsh-clarification#comment-624 Scott Boyson Fri, 27 Apr 2012 15:27:43 +0000 http://ekwestrel.com/?p=156#comment-624 Nice overview. of NPSH. Personally, I think manufacturers should not add their on margin of safety on published curves for NPSHr. NPSHr has a clear definition of 3% head loss. Safety factors should be left to the system designer or as a note at the bottom of the published curves.Not only is the NPSH term often misunderstood but how to measure it in an existing system can be confusing. The issue often revolves around the fact that NPSH is an absolute pressure measurement. In open tank suction conditions, you have one atmosphere of pressure contributing to positive NPSHA. We so often think in gauge pressures or pressure differerential conditions that this tends to be confusing for those that do not work with pumps often. Nice overview. of NPSH. Personally, I think manufacturers should not add their on margin of safety on published curves for NPSHr. NPSHr has a clear definition of 3% head loss. Safety factors should be left to the system designer or as a note at the bottom of the published curves.

Not only is the NPSH term often misunderstood but how to measure it in an existing system can be confusing. The issue often revolves around the fact that NPSH is an absolute pressure measurement. In open tank suction conditions, you have one atmosphere of pressure contributing to positive NPSHA. We so often think in gauge pressures or pressure differerential conditions that this tends to be confusing for those that do not work with pumps often.

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