ANSI/HI 9.6.1-2024

Rotodynamic Pumps Guideline for NPSH Margin

The guideline explains the concept of net positive suction head (NPSH), which characterizes the suction conditions of rotodynamic pumps. It focuses on two key components:  - NPSHA – A system-specific characteristic determined by the system designer. - NPSHR – A pump-specific requirement specified by the pump manufacturer.  To ensure optimal performance, the system supplied NPSHA must always exceed the pump’s - NPSHR. Emphasis is placed on maintaining an appropriate NPSH margin, as insufficient margins can lead to noise, vibration, performance degradation, and reduced pump reliability.  This guideline is globally applicable, assisting engineering firms in designing reliable pump systems and selecting pumps that meet operational requirements. Recommended minimum NPSH margins are provided for various applications within the following market segments:  - Petroleum (hydrocarbon) process pumps - Chemical process pumps - Electric power plant (non-nuclear) pumps - Water and wastewater pumps - Pulp and paper stock pumps - Slurry pumps - Oil and gas pumps - Irrigation pumps - General service pumps - Building services pumps  What’s New: This standard supersedes the ANSI/HI 9.6.1-2017 edition. Updates in the new edition include:  - Transition from the use of NPSH3 to NPSHR for NPSH margin determination. - The pump manufacturer’s supplied NPSHR value will be greater than or equal to the tested NPSH3 value. - Revision to the NPSH margin considerations section. - Elimination of the NPSH margin determination section. - Coordination of the applications section with the NPSH margin considerations. - Appendices were replaced with new NPSH margin focused/related topics applicable to all market segments(NPSHA Determination and Considerations, and Compensating for Insufficient NPSH Margin).