AFT Product Tips
It’s a Pump Properties Party!
Everyone loves to celebrate. Here at AFT, we are celebrating the release of AFT Fathom 10. One of the great things about AFT Fathom 10 is that the new and improved Pump Properties window makes specifying pumps faster and easier than ever. This blog will provide an overview of the features that have been added or changed within the Pump Properties window, so that you can get a head start on defining pumps in AFT Fathom 10!
Positive Displacement Pump Model
There are now two distinct pump models in the Pump Properties window:
The addition of the Positive Displacement (PD) pump model clarifies the specification of this pump type and makes it easier for users to input the required data.
As shown in Figure 2, part of the new Positive Displacement pump model is the option to specify "Acceleration Head/Pressure Parameters."
Acceleration head is the energy required to change the velocity of the fluid in the system from zero to some non-zero velocity. This requires additional energy beyond the amount required simply to overcome the frictional losses in a system. PD pumps are constantly accelerating and decelerating the fluid in the suction line, which makes this feature useful.
Centrifugal Pump Analysis Types
When the user selects a Centrifugal (Rotodynamic) pump, there are now two Analysis Types available:
The Analysis Types clarify the required data and intention of the model. For example, if the user already has a pump curve, they would select "Pump Curve" and click the "Enter Curve Data" button. This opens the Pump Configuration window, where the curve data can be entered, as shown in Figure 3.
If the user is sizing a pump, however, they would select "Sizing," which allows users to fix one parameter, as shown in Figure 4. AFT Fathom will then calculate the other parameters, helping to size the pump.
Preferred and Allowable Operating Regions
The Configuration Data tab of the Pump Configuration window now includes the option to specify Preferred and/or Allowable Operating Regions. This feature helps the user to quickly determine if a centrifugal pump's behavior is acceptable.
The Preferred Operating Region (POR) is a percentage of BEP range. If the pump operates outside of this range, there will be a warning in the Output. The percentage of BEP range can come from three sources:
1. HI 9.6.3-2017, based on the specific speed of the pump
2. ANSI/API 610 11th Edition (2010)
3. User Specified
The Allowable Operating Region (AOR) is a volumetric flow range. If the pump operates outside of this range, there will be a warning in the Output. The flow range is User Specified.
In addition to providing warnings in the Output, POR and AOR values can be plotted on Pump vs. System curves in the Graph Results.
Interstage Bleed/Takeoff Flow Pump Model
Some multiple stage centrifugal pumps can have flow removed at an intermediate point. For such pumps, the manufacturer provides two pump curves:
1. Overall Pump Curve – The total dynamic head from the suction of the first stage to the discharge of the last stage when the takeoff flow is zero
2. Takeoff Pump Curve – The total dynamic head of the stages before the takeoff point
The new "Interstage Bleed/Takeoff Flow" feature allows the user to directly enter these manufacturer pump curves without any manual calculations.
In summary, the Pump Properties window in AFT Fathom 10 makes it easier to specify pumps by clarifying the user input needed for each type. It also includes new features, expanding the versatility of the existing pump models. Now that's something to celebrate!
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