PARSIPPANY, NJ -- The Hydraulic Institute (HI) has published “ANSI/HI 9.6.1–2012 Rotodynamic Pumps Guideline for NPSH Margin.” The new guideline serves as a replacement for the 1998 edition, which was later withdrawn completely in 2003.

This guideline covers rotodynamic, general-purpose pumps with power levels as high as 5300 hp and impeller tip speeds less than 130 feet per second, and describes the benefits to pump longevity of maintaining suitable NPSH margin.

The document serves as a tutorial on the subject of NPSH as well as providing guidance for determining NPSH margin. The following considerations are discussed relative to the sensitivity of a pump to NPSH-related problems: impeller inlet tip speed, larger vs. smaller impeller eye diameter, suction-specific speed, characteristics of the pumpage, operating range of the pump and proximity to POR and AOR, materials of construction and cavitation resistance, impeller vane overlap, pump size and relationship of size to cavitation damage, duty cycle (time of operation under cavitating condition), and reduction of NPSHA with time.

The NPSH reference helps pump users understand why it is essential to specify an appropriate NSPH margin and learn about the negative aspects of specifying an excessive NPSH margin.

The updated guideline is available for purchase at the HI eStore. Visit for more information.     

The Hydraulic Institute has also introduced CD Version 3.1, its latest offering of ANSI/HI standards presented in CD format. An update of an earlier CD offering, the new release contains a full set of all 31 current standards on one CD. Orders for the new CD are now being expedited via the HI eStore.