ANSI/HI 9.6.7-2015 pdf free download

ANSI/HI 9.6.7-2015 pdf free download.Rotodynamic Pumps – Guideline for Effects of Liquid Viscosity on Performance.
9.6.7.3.2 Methods for determining correction factors Correction factors can be either defined empirically from a data bank containing measurements on various pumps with water and liquids of different viscosities or from a physical model based on the analysis of the energy losses in the pump. Examples of such loss analysis methods are given in references 9, 10, 11 , and 23 of the bibliography. Analysis of the limited data available shows that empirical and loss analysis methods predict head correction func- tions with approximately the same accuracy. Loss analysis methods are, however, more precise in predicting power requirements for pumping viscous liquids. It is also possible to investigate the influence of various design parame- ters on viscous performance and to optimize pump selection or design features for operation with highly viscous liq- uids by applying the loss analysis procedures. Further theoretical explanations of the principles of loss analysis methods are given in Section 9.6.7.5. Use of such methods may require more information about pump dimensions than is generally available to the user. A loss anal- ysis procedure may be expected to provide more accurate predictions of pump performance with viscous liquids when such detailed information is available. The HI method explained in Section 9.6.7.4 is based on empirical data. It provides a way of predicting the effects of liquid viscosity on pump performance with adequate accuracy for most practical purposes. The method in this doc- ument gives correction factors similar to the previous HI method. The new method matches the experimental data better than the old HI method that has been widely used throughout the world for many years. The standard devia- tion for the head correction factor, C H , is 0.1. Estimates of viscous power, P vis , are subject to a standard deviation of 0.1 5. 9.6.7.4 Synopsis of Hydraulic Institute method
The correction equations are, therefore, a generalized method based on empirical data, but are not exact for any particular pump. The generalized method may be applied to pump performance outside the range of test data indi- cated above, as outlined in Section 9.6.7.4 and with the specific instructions and examples in Sections 9.6.7.4.5 and 9.6.7.4.6. Extrapolating the method to larger pumps will tend to give conservative performance predictions because larger pumps, at any given speed and viscosity, imply higher Reynolds numbers and lower viscous correc- tions. When more accurate information is essential, pump performance tests should be conducted with the particular vis- cous liquid to be handled. Prediction methods based on an analysis of hydraulic losses for a particular pump design may also be more accurate than this generalized method. 9.6.7.4.2 Viscous liquid performance correction limitations The correction factors are applicable to pumps of hydraulic design with essentially radial impeller discharge (n s ≤ 60, N s ≤ 3000), in the normal operating range, with fully open, semi-open, or closed impellers with either a single or double suction entry. Do not use these correction factors for axial flow type pumps or for pumps of special hydraulic design. See Section 9.6.7.6 for additional guidance. Use correction factors only where an adequate margin of NPSH available (NPSHA) over NPSH3 is present in order to cope with an increase in NPSH3 caused by the increase in viscosity. See Section 9.6.7.5.3 to estimate the increase in NPSH3. The data used to develop the correction factors are based on tests of Newtonian liquids. Gels, slurries, paper stock, and other non-Newtonian liquids may produce widely varying results, depending on the particular characteristics of the liquids. 9.6.7.4.3 Symbols and definitions used for determining correction factors See Section 9.6.7.8 for all notation definitions. Other technical expressions are defined in HI Standards. Equations for converting kinematic viscosity from SSU to cSt