The 1997 edition of the ANSI/HI standard on allowable operating region for centrifugal and vertical pumps has been updated by the Hydraulic Institute, Parsippany, N.J. The organization published ANSI/HI 9.6.3,2012 Rotodynamic (Centrifugal and Vertical) Pumps – Guideline for Allowable Operating Region, to delineate the changes.

The updated guideline discusses the effects of operating a rotodynamic pump at rates of flow greater than or less than the rate of flow at the pump’s best efficiency point (BEP). These effects influence the power consumption and life of pump components; therefore, considering the operating rate of flow is essential to reliable, efficient pump operation. The preferred operating region (POR) and the allowable operating region (AOR) are defined for rotodynamic pump types and related to specific speed. Factors that affect AOR are discussed and NPSH margin vs. rate of flow is presented.

The guideline also indicates when stable or unstable operation may be expected based on typical system head curves, for pumps exhibiting a drooping head curve or a head curve with a dip.. The guideline is available for purchase at the HI eStore for $65 and is available in both hardcopy and pdf formats.