HI 9.6.1-2024

This standard applies to rotodynamic pumps and defines how to calculate net positive suction head (NPSH) margin and recommends NPSH margin for these pumps based on specific application considerations, pump design, and the flow relative to the best efficiency point (BEP). NPSH margin above the pumps required NPSH is needed for reliable operation. NPSH margin recommendations are provided for petroleum (hydrocarbon) process pumps, chemical process pumps, electric power plant pumps, water/wastewater pumps, pulp and paper stock pumps, slurry pumps, oil and gas, and building services pumps.

This standard applies to all markets worldwide and aids the engineering firm in designing a pump system and selecting a pump that will operate reliably.

This edition of the guideline supersedes the 2017 edition. Major updates in this 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.