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Model Pump Curve Families with Multiple Pump Configurations

Posted in AFT Fathom, AFT Arrow, AFT Titan, AFT Impulse, AFT Mercury

You've probably modeled pumps using curve data from the manufacturer. In conjunction with specifying a name reflecting the pump make and model and saving pumps to your component database, selecting and using these pump junctions in your system models is fast and easy. Often, however, a make/model pump will have not one set of head/pressure, efficiency and NPSHR curves, but a family of curves for various operating speeds and impeller diameters. You could define a pump junction for each set of curves, but with Multiple Pump Configurations, you can readily save the entire family of curves in one pump junction.

For simplicity's sake we'll refer to pumps here, but this tip works equally well for both pumps in AFT Fathom, AFT Mercury and AFT Impulse, and compressors/fans in AFT Arrow.

Let's first review how you model pump curves for one combination of speed and impeller diameter.

  1. Select the 'Pump Curve' option in the pump specifications window.
  2. Click on the 'Pump Configurations' button which opens the Pump Configuration window
  3. Enter data for the head/pressure curve and, optionally, the efficiency and NPSHR curves.
  4. Select which data you want to curve fit and click 'Generate Curve Fit'.

Looking at the upper lefthand corner of the Pump Configuration window you'll see two options; "Simple (configuration)", the default, and "Multiple Configurations". Selecting Multiple Configurations the Pump Configuration window will expand, revealing an area describing the configurations that have been defined.

A pump configuration is a set of curves describing the pump performance for a specific speed and impeller diameter (i.e. head/pressure and, optionally, efficiency and NPSHR). Configurations defined are listed by RPM and impeller diameter.

Let's say you want to enter the curves for 1750 RPM using 6" and 8" impellers and 3550 RPM using 4" and 5" impellers.

  1. Within the Pump Configuration window with 'Multiple Configurations' selected, click the 'Create' button in the configurations area
  2. Input 1750 for RPM and 6" for impeller diameter (these can be entered in any order and you can always add, delete or modify configurations).
  3. Fill in the curve data for this pump speed and impeller diameter and fit the curves by clicking the 'Generate Curve Fit Now' button. To complete defining the configuration, click 'Update Configuration Now' (you'll note this area is highlighted to remind of this final step). The 'Pump Configurations Defined' area will now list '1750 RPM' and '6 inches'
  4. We'll now add the 1750 RPM / 8" data by clicking 'Create', selecting 1750 RPM from the dropdown list (which will contain all speeds we've defined), input 8" for the impeller diameter, then enter and curve fit the data and click 'Update Configuration Now'.

Repeat the above for the two 3550 RPM impeller sizes and you'll see all four configurations listed in the 'Pump Configurations Defined' area.

With multiple configurations defined, you'll now see 'RPM' and 'Impeller' drop down lists in the pump specifications window containing all the configurations defined. Changing from one set of pump curves to another is as fast and easy as selecting the desired speed and diameter from these lists.

Multiple pump configurations let you effectively model an entire family of curves in one pump junction. Coupled with the ability to store pumps in the Component Database, one can easily build and share a comprehensive database of the pumps you use.

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